HomeMy WebLinkAboutGeomorphic Analysis of Mattituck Inlet & Goldsmith Inlet - 2005
ER
D
C
/
C
H
L
T
R
-
0
5
-
2
Geomorphic Analysis of Mattituck Inlet and
Goldsmith Inlet, Long Island, New York
Michael J. Morgan, Nicholas C. Kraus,
and Jodi M. McDonald
July 2005
Co
a
s
t
a
l
a
n
d
H
y
d
r
a
u
l
i
c
s
L
a
b
o
r
a
t
o
r
y
Approved for public release; distribution is unlimited.
Coastal Inlets
Research Program
ERDC/CHL TR-05-2
July 2005
Geomorphic Analysis of Mattituck Inlet and
Goldsmith Inlet, Long Island, New York
Michael J. Morgan
Department of Geography
Hunter College, City University of New York
695 Park Avenue
New York, NY 10021
Nicholas C. Kraus
Coastal and Hydraulics Laboratory
U.S. Army Engineer Research and Development Center
3909 Halls Ferry Road
Vicksburg, MS 39180-6199
Jodi M. McDonald
U.S. Army Engineer District, New York
26 Federal Plaza
New York, NY 10278-0090
Final report
Approved for public release; distribution is unlimited.
Prepared for U.S. Army Corps of Engineers
Washington, DC 20314-1000
ABSTRACT: This study of Mattituck Inlet and Goldsmith Inlet, Long Island, NY, covers the historic and geomor-
phic background, literature, field measurements, numerical modeling of tidal circulation, and analysis of inlet mor-
phologic properties. The inlets are located 8.2 km apart on the eastern end of the north shore of Long Island, NY,
facing Long Island Sound Mattituck Inlet has a federally maintained channel and dual jetties, and it connects the
sound to Mattituck Creek. Mattituck Inlet is the only major harbor on the north fork of Long Island is a commercial
and recreational boating center. The navigation channel is maintained to a depth of 7 ft mean low water with a 2-ft
allowable overdraft. Goldsmith Inlet connects the sound to Goldsmith Pond. The inlet has a nonfunctional jetty on
its west side and is non-navigable, with typical depths ranging from 0.5 to 3 ft.
Tidal inlets on the north shore of Long Island have received little study compared to those on the south shore that
open to the Atlantic Ocean. It appears that most inlets on the north shore have been more stable and in existence
longer than the inlets on the south shore. Inlets on the north shore, therefore, hold value for further understanding of
basic inlet processes, in particular, of channel cross section and locational stability. Another motivation for the study
of inlets along the north shore of Long Island is the large range in grain size of the sediments on this coast.
Given their significant differences, it is remarkable that Mattituck Inlet and Goldsmith Inlet have remained open
for more than two centuries and likely much longer. The stability of inlets on the north shore derives in part from a
relatively steep inner shore face, presence of geologic controls such as glacial erratics or hard points on shore, ori-
gins of ponds as low-lying areas created after glaciation, and relatively weak longshore sediment transport that is
about an order of magnitude less than that on the south shore of Long Island. However, other factors enter in con-
trolling stability, in particular, commercial mining of sediment, such as at Mattituck Inlet.
.
DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes.
Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products.
All product names and trademarks cited are the property of their respective owners. The findings of this report are not
to be construed as an official Department of the Army position unless so designated by other authorized documents.
DESTROY THIS REPORT WHEN IT IS NO LONGER NEEDED. DO NOT RETURN TO THE ORIGINATOR.
iii
Contents
Preface .............................................................................................................. xxii
Conversion Factors Non-SI to SI Units of Measurement................................. xxiv
1⎯Introduction......................................................................................................1
Background......................................................................................................1
Study Site.........................................................................................................3
Previous Studies...............................................................................................6
Motivaton.........................................................................................................9
Study Objective..............................................................................................10
2⎯Study Area and Physical Setting....................................................................12
Regional Setting - Long Island Sound...........................................................12
Geomorphic environment........................................................................12
Oceanographic environment....................................................................15
Longshore sediment transport.................................................................18
Mattituck Inlet - History and Site Description...............................................20
Physical description.................................................................................22
Physical setting........................................................................................27
Goldsmith Inlet - History and Site Description .............................................32
Physical description.................................................................................35
Physical setting........................................................................................39
Present condition.....................................................................................40
3⎯Field Data Collection and Analysis................................................................46
Overview of Measurements and Vertical Datums.........................................46
Mattituck Inlet................................................................................................49
Bathymetry..............................................................................................49
Water level ..............................................................................................65
Current.....................................................................................................68
Sediment..................................................................................................69
Goldsmith Inlet..............................................................................................74
Bathymetry..............................................................................................74
Water level ..............................................................................................88
Current.....................................................................................................91
Sediment..................................................................................................92
iv
4⎯Morphology Change, and Channel Shoaling and Migration........................101
Mattituck Inlet..............................................................................................101
Offshore morphology change................................................................101
Navigation channel and flood shoal morphology change .....................117
East bank spit migration........................................................................162
Bank encroachment analysis.................................................................164
Goldsmith Inlet............................................................................................168
Offshore morphology change................................................................168
Channel migration.................................................................................174
Channel and flood shoal morphology change.......................................187
Summary of morphology change at Goldsmith Inlet............................200
5⎯Circulation Analysis.....................................................................................204
Mattituck Inlet..............................................................................................204
Model validation ...................................................................................206
Pre-dredging condition (2002) ..............................................................213
Alterntive 1: Post-dredging morphology..............................................222
Alterntive 2: Natural morphology with offshore shoal ........................228
Goldsmith Inlet............................................................................................243
Model validation ...................................................................................243
Discussion of tidal asymmetry..............................................................249
Discussion of current velocity...............................................................255
6⎯Inlet Morphology and Stability ....................................................................265
General Inlet Properties...............................................................................265
Inlet classification and sedimentation patterns......................................265
Inlet stability..........................................................................................268
Hydraulic efficiency..............................................................................269
Ebb shoal volume..................................................................................270
Flood shoal volume...............................................................................270
Mattituck Inlet..............................................................................................271
Mattituck Inlet channel cross-sectional area stability ...........................272
Mattituck Inlet offshore shoal ...............................................................275
Mattituck Inlet flood shoal....................................................................276
Goldsmith Inlet............................................................................................278
Goldsmith Inlet channel cross-sectional area stability..........................279
Goldsmith Inlet ebb shoal......................................................................282
Goldsmith Inlet flood shoal...................................................................282
Discussion of Channel Cross-Sectional Area Relations..............................284
7⎯Comparative Analysis and Conclusions.......................................................286
Summary of Inlet Characteristics.................................................................287
Comparative Analysis..................................................................................288
Forcing ..................................................................................................288
General features of geomorphology......................................................289
v
Anthropogenic influences......................................................................290
Hydrodynamic and tidal shoals.............................................................291
Channel cross-sectional area stability ...................................................291
Mattituck Inlet, Conclusions........................................................................292
Goldsmith Inlet, Conclusions.......................................................................294
Recommendations for Future Studies..........................................................295
References..........................................................................................................297
List of Figures
Figure 1-1. Long Island, NY, inlets and harbors................................................4
Figure 1-2. Long Island, NY, with study area inset...........................................5
Figure 1-3. Study area with Mattituck Inlet and Goldsmith Inlet insets............5
Figure 1-4. Mattituck Inlet and Mattituck Creek, 16 April 2003.......................6
Figure 1-5. Goldsmith Inlet and Goldsmith Pond, 16 April 2003......................7
Figure 1-6. Shoreline from Duck Pond Point to Horton Point...........................8
Figure 1-7. Goldsmith Inlet with view northeast into Long Island Sound,
showing substantial gravel and cobble, 22 March 2003................10
Figure 2-1. Long Island Sound region bathymetry ..........................................13
Figure 2-2. Harbor Hill and Ronkonkoma Moraine locations .........................14
Figure 2-3. Study area headlands.....................................................................15
Figure 2-4. Mattituck Inlet as depicted in NOS T-sheet 55 (1838)..................21
Figure 2-5. Mattituck Inlet and northern end of Mattituck Creek,
11 May 1955..................................................................................21
Figure 2-6. The Mattituck Mill at Mattituck Creek..........................................22
Figure 2-7. Dredging and mining activities in and near Mattituck Inlet..........23
Figure 2-8. Mattituck Inlet and jetties, view looking south,
28 March 2003...............................................................................26
Figure 2-9. Mattituck Inlet and jetties, view looking north,
28 March 2003...............................................................................26
Figure 2-10. Mattituck Inlet channel, after turn eastward inside jetties.............27
Figure 2-11. Bluffs east of Mattituck Inlet, 21 November 2003........................28
Figure 2-12. Bailie’s Beach primary dune, 21 November 2003.........................29
Figure 2-13. Dunes east of Mattituck Inlet, looking west, 8 October 2002.......29
vi
Figure 2-14. Dunes at base of Mattituck Inlet east jetty, looking south,
21 November 2003........................................................................30
Figure 2-15. Dunes at base of Mattituck Inlet east jetty, looking north,
8 October 2003..............................................................................30
Figure 2-16. Vegetated dune protected by revetment at Bailie’s Beach, view
looking east, 9 July 2004...............................................................31
Figure 2-17. Sparsely vegetated and unprotected dune at Bailie’s Beach,
view looking west, 9 July 2004.....................................................31
Figure 2-18. Mattituck Inlet perimeter, view looking south,
21 November 2003........................................................................32
Figure 2-19. Goldsmith Inlet as depicted in NOS T-sheet 55 (1838) ................33
Figure 2-20. Peconic Mill at Goldsmith Inlet.....................................................34
Figure 2-21. Headstone of James H. and Sarah C. Goldsmith, Old Burial
Ground, Southold, New York........................................................35
Figure 2-22. Goldsmith Inlet and Goldsmith Pond, 11 May 1955, 9 years
before jetty construction................................................................36
Figure 2-23. Typical gravel and some cobble armoring at Goldsmith Inlet,
28 March 2003...............................................................................37
Figure 2-24. Proposed marinas, 1960.................................................................37
Figure 2-25. Goldsmith Inlet, west perimeter, view looking south,
circa winter 2001...........................................................................39
Figure 2-26. Bluffs west of Goldsmith Inlet, 28 March 2003............................40
Figure 2-27. Goldsmith Inlet entrance with view of east beach,
28 March 2003...............................................................................40
Figure 2-28. Sediment impoundment west of Goldsmith Inlet jetty, circa
winter 2001....................................................................................42
Figure 2-29. Goldsmith Inlet orientation, 8 October 2002.................................43
Figure 2-30. Goldsmith Inlet orientation, 28 March 2003.................................43
Figure 2-31. Goldsmith Inlet orientation and ice, 16 February 2004.................44
Figure 2-32. Goldsmith Inlet orientation after emergency dredging,
6 April 2004...................................................................................44
Figure 3-1a. Datum elevation differences, Port Jefferson..................................47
Figure 3-1b. Datum elevation differences, Bridgeport.......................................48
Figure 3-2. Mattituck Inlet bathymetry survey coverage, 6-8 October
2002...............................................................................................50
Figure 3-3. Mattituck Inlet elevation contours, 6-8 October 2002...................51
Figure 3-4. Mattituck Inlet offshore west survey transects, 6-8 October
2002...............................................................................................52
vii
Figure 3-5a. Beach profiles W1-W5, west of Mattituck Inlet,
6-8 October 2002...........................................................................52
Figure 3-5b. Beach profiles W6-W10, west of Mattituck Inlet,
6-8 October 2002...........................................................................53
Figure 3-6. Shoreline west of Mattituck Inlet, 21 November 2003..................53
Figure 3-7a. Longshore bars west of Mattituck Inlet, 16 April 2003.................54
Figure 3-7b. Offshore east of Mattituck Inlet, 16 April 2003............................54
Figure 3-8. Mattituck Inlet offshore east survey transects, 6-8 October
2002...............................................................................................55
Figure 3-9a. Beach profiles E1-E5, east of Mattituck Inlet, 6-8 October
2002...............................................................................................56
Figure 3-9b. Beach profiles E6-E10, east of Mattituck Inlet,
6-8 October 2002...........................................................................56
Figure 3-10. Beach east of Mattituck Inlet, 16 April 2003, showing
irregular shoreline..........................................................................57
Figure 3-11 Cuspate shoreline features east of Mattituck Inlet,
21 November 2003........................................................................57
Figure 3-12. Mound of Crepidula fornicata shells, east of Mattituck
Inlet, 21 November 2003...............................................................58
Figure 3-13. Mattituck Inlet offshore shoal and channel contour
elevation, 6-8 October 2002 ..........................................................59
Figure 3-14. Features offshore of Mattituck Inlet, 6-8 October 2002................59
Figure 3-15. Mattituck Inlet flood shoal, 6-8 October 2002..............................60
Figure 3-16. Mattituck Inlet flood shoal on eastern bank, view looking
west, March 2003 ..........................................................................60
Figure 3-17. Mattituck Inlet flood shoal on eastern bank, view looking
east, 21 November 2003................................................................61
Figure 3-18. Mattituck Inlet Federal navigation channel elevation,
6-8 October 2002...........................................................................62
Figure 3-19. Mattituck Inlet channel transects 1-10, 6-8 October 2002.............62
Figure 3-20a. Mattituck Inlet channel cross sections 1-4, 6-8 October
2002...............................................................................................63
Figure 3-20b. Mattituck Inlet channel cross sections 5-7, 6-8 October
2002...............................................................................................63
Figure 3-20c. Mattituck Inlet channel cross sections 8-10, 6-8 October
2002...............................................................................................64
Figure 3-21. Mattituck Inlet shore-attached flood shoals on northern
and southern banks of channel, view looking east,
21 November 2003........................................................................64
viii
Figure 3-22. Mattituck Inlet tide gauge and current meter locations,
19 September – 8 October 2002....................................................65
Figure 3-23a. Mattituck Inlet water level, 19 September – 8 October
2002...............................................................................................66
Figure 3-23b. Mattituck Inlet water level, 4-8 October 2002...............................67
Figure 3-24. Mattituck Inlet along-channel current velocity,
7-8 October 2002...........................................................................68
Figure 3-25. Mattituck Inlet sediment sample locations, 6-7 May 2003............70
Figure 3-26a. Mattituck Inlet cumulative grain size distribution MH1-MH4,
6-7 May 2003 ................................................................................71
Figure 3-26b. Mattituck Inlet cumulative grain size distribution MH5, MH6,
MH8, and MH10, 6-7 May 2003...................................................71
Figure 3-27. Mattituck Inlet, New York District (1969) sediment
sampling profile locations .............................................................72
Figure 3-28a Goldsmith Inlet bathymetry survey coverage,
6-8 October 2002...........................................................................75
Figure 3-28b. Goldsmith Inlet elevation contours, 6-8 October 2002 .................75
Figure 3-29. Goldsmith Inlet offshore survey transects, 6-8 October
2002...............................................................................................76
Figure 3-30a. Beach profiles W1-W3, west of Goldsmith Inlet,
6-8 October 2002...........................................................................77
Figure 3-30b. Beach profiles W4-W7, west of Goldsmith Inlet,
6-8 October 2002...........................................................................77
Figure 3-31a. Beach profiles E1-E5, east of Goldsmith Inlet, 6-8 October
2002...............................................................................................78
Figure 3-31b. Beach profiles E6-E10, east of Goldsmith Inlet,
6-8 October 2002...........................................................................78
Figure 3-32. Aerial view of shoreline west of Goldsmith Inlet, 16 April
2003...............................................................................................79
Figure 3-33. Ground view of shoreline west of Goldsmith Inlet,
28 March 2003...............................................................................79
Figure 3-34. Aerial view of shoreline east of Goldsmith Inlet, 16 April
2003...............................................................................................80
Figure 3-35. Ground view of inlet entrance and shoreline east of
Goldsmith Inlet, 28 March 2003....................................................80
Figure 3-36. Goldsmith Pond flood shoal formations, 16 April 2003................81
Figure 3-37. Goldsmith Inlet flood shoal, west lobe, view looking
south, 28 March 2003....................................................................81
Figure 3-38. Goldsmith Inlet flood shoal, east lobe, view looking south,
9 July 2004 ....................................................................................82
ix
Figure 3-39. Goldsmith Inlet flood shoal, east and west lobe, view
looking south, 9 July 2004.............................................................82
Figure 3-40a. Goldsmith Inlet contours at low tide, 8 October 2002...................83
Figure 3-40b. Goldsmith Inlet contours at mean tide, 8 October 2002................83
Figure 3-40c. Goldsmith Inlet contours at high tide, 8 October 2002 .................84
Figure 3-41. Goldsmith Inlet, channel with shoal, 28 March 2003....................85
Figure 3-42. Goldsmith Inlet attached shoal, 28 March 2003............................85
Figure 3-43. Goldsmith Inlet channel transects, 8 October 2002.......................86
Figure 3-44a. Goldsmith Inlet channel cross sections 1-4, 8 October 2002 ........86
Figure 3-44b. Goldsmith Inlet channel cross sections 5-8, 8 October 2002 ........87
Figure 3-44c. Goldsmith Inlet channel cross sections 9-12, 8 October 2002 ......87
Figure 3-45. Goldsmith Inlet channel center-line elevation, 8 October 2002....88
Figure 3-46. Goldsmith Inlet tide gauge locations, 19 September - 8 October
2002...............................................................................................89
Figure 3-47a. Goldsmith Inlet water level, 19 September – 8 October 2002.......89
Figure 3-47b. Goldsmith Inlet water level, 5-7 October 2002.............................90
Figure 3-48. Goldsmith Inlet midchannel current velocity, 8 October 2002 .....92
Figure 3-49a. Goldsmith Inlet sediment sample locations, 8 October 2002........93
Figure 3-49b. Goldsmith Inlet sediment sample locations, 31 July 2003............93
Figure 3-50a. Goldsmith Inlet cumulative grain size S1-S4 and S15, 8 October
2002 and 31 July 2003...................................................................94
Figure 3-50b. Goldsmith Inlet cumulative grain size S5-S8 and S16, 8 October
2002 and 31 July 2003...................................................................94
Figure 3-50c. Goldsmith Inlet cumulative grain size S9-S12 and S17, 8 October
2002 and 31 July 2003...................................................................95
Figure 3-50d. Goldsmith Inlet cumulative grain size S13, S14, S18, S19,
8 October 2002 and 31 July 2003..................................................95
Figure 3-50e. Goldsmith Inlet cumulative grain size S20-S23, 8 October 2002
and 31 July 2003............................................................................96
Figure 3-50f. Goldsmith Inlet cumulative grain size S24-S27, 8 October 2002
and 31 July 2003............................................................................96
Figure 3-50g. Goldsmith Inlet cumulative grain size S28-S31, 8 October 2002
and 31 July 2003............................................................................97
Figure 3-51. Goldsmith Inlet median grain-size distribution of surface
samples, 8 October 2002 and 31 July 2003...................................98
Figure 3-52. Goldsmith Inlet, New York District (1969) profile locations......100
Figure 4-1a. Beach profile W1, west of Mattituck Inlet, March 1998 and
6-8 October 2002.........................................................................102
x
Figure 4-1b Beach profile W2, west of Mattituck Inlet, March 1998 and
6-8 October 2002.........................................................................102
Figure 4-1c. Beach profile W3, west of Mattituck Inlet, March 1998 and
6-8 October 2002.........................................................................103
Figure 4-1d. Beach profile W4, west of Mattituck Inlet, March 1998 and
6-8 October 2002.........................................................................103
Figure 4-1e. Beach profile W5, west of Mattituck Inlet, March 1998 and
6-8 October 2002.........................................................................104
Figure 4-1f. Beach profile W6, west of Mattituck Inlet, March 1998 and
6-8 October 2002.........................................................................104
Figure 4-1g. Beach profile W7, west of Mattituck Inlet, March 1998 and
6-8 October 2002.........................................................................105
Figure 4-1h Beach profile W8, west of Mattituck Inlet, March 1998 and
6-8 October 2002.........................................................................105
Figure 4-2a. Offshore shoal cross-shore profile E4, March 1998 and
6-8 October 2002.........................................................................106
Figure 4-2b. Offshore shoal cross-shore profile E5, March 1998 and
6-8 October 2002.........................................................................106
Figure 4-2c. Offshore shoal cross-shore profile E6, March 1998 and
6-8 October 200...........................................................................107
Figure 4-2d. Offshore shoal cross-shore profile E7, March 1998 and
6-8 October 2002.........................................................................107
Figure 4-2e. Offshore shoal cross-shore profile E8, March 1998 and
6-8 October 2002.........................................................................108
Figure 4-2f. Offshore shoal cross-shore profile E9, March 1998 and
6-8 October 2002.........................................................................108
Figure 4-3. Mattituck Inlet and offshore elevation contours,
8 December 1927.........................................................................110
Figure 4-4. Mattituck Inlet, circa 1930 and offshore elevation contours,
1969.............................................................................................110
Figure 4-5a. Mattituck Inlet offshore elevation change, 1927-1969................111
Figure 4-5b. Mattituck Inlet offshore elevation change, 1969-2002................111
Figure 4-5c. Mattituck Inlet offshore elevation change, 1927-2002................112
Figure 4-6. Volume change polygons, east of Mattituck Inlet,
with elevation change 1927-2002................................................113
Figure 4-7. Offshore shoal elevation change, 1969-2002 and Mattituck
Inlet 16 April 2003 ......................................................................114
Figure 4-8. Mattituck Inlet offshore shoal center lines,
8 December 1927 and 6-8 October 2002.....................................116
Figure 4-9. Offshore feature center lines, 8 December 1927
and 6-8 October 2002..................................................................117
xi
Figure 4-10. Mattituck Inlet orientation, 1891.................................................119
Figure 4-11. Mattituck Inlet orientation, 1900.................................................119
Figure 4-12. Mattituck Inlet, 1891-1900, hypothesized reorientation..............120
Figure 4-13. Mattituck Inlet orientation, 1901.................................................121
Figure 4-14. Mattituck Inlet orientation, 1905-1907........................................121
Figure 4-15. Mattituck Inlet orientation, 1913/14............................................122
Figure 4-16. Mattituck Inlet with shoaling along inside of west jetty,
circa 1930s...................................................................................123
Figure 4-17. Mattituck Inlet east jetty landward breach, 1941.........................123
Figure 4-18a. Mattituck Inlet channel elevation, 1935......................................127
Figure 4-18b. Mattituck Inlet flood shoal area, 1935.........................................127
Figure 4-19a. Mattituck Inlet channel elevation, 4 May 1936...........................128
Figure 4-19b. Mattituck Inlet flood shoal area, 4 May 1936..............................129
Figure 4-19c. Channel elevation change, 1935 to 4 May 1936..........................129
Figure 4-20. Federal navigation channel study area.........................................130
Figure 4-21a. Mattituck Inlet channel elevation, 3 July 1937............................131
Figure 4-21b. Mattituck Inlet flood shoal area, 3 July 1937..............................132
Figure 4-21c. Channel elevation change, 4 May 1936 to 3 July 1937...............132
Figure 4-22a. Mattituck Inlet channel elevation, 1938......................................133
Figure 4-22b. Mattituck Inlet flood shoal area, 1938.........................................134
Figure 4-22c. Channel elevation change, 4 May 1936 to 1938 .........................134
Figure 4-23a. West lobe morphology change, 1936–1938................................135
Figure 4-23b. East lobe morphology change, 1936–1938..................................135
Figure 4-24. Mattituck Inlet west jetty seaward extension, 1938.....................136
Figure 4-25 Shoreline recession and east jetty landward breach
1927 to 1941................................................................................137
Figure 4-26a. Mattituck Inlet east bank spit morphology, 1891-1927, with
jetty configuration of 1914 included for reference......................138
Figure 4-26b. Mattituck Inlet east bank spit morphology, 1935-1955, with
jetty configuration of 1914 and 1946 included for reference......139
Figure 4-27. Mattituck Inlet Federal navigation channel configuration,
prior to and after October – November 1950...............................140
Figure 4-28. Federal navigation channel and Federal anchorage
dredging areas, September – October 1965.................................141
Figure 4-29a. Mattituck Inlet, circa 1930...........................................................142
Figure 4-29b. Mattituck Inlet, 1938...................................................................142
xii
Figure 4-29c. Mattituck Inlet, 1941...................................................................143
Figure 4-29d. Mattituck Inlet, 11 May 1955......................................................143
Figure 4-29e. Mattituck Inlet, 1 April 1964.......................................................144
Figure 4-29f. Mattituck Inlet, 25 April 1969.....................................................144
Figure 4-29g. Mattituck Inlet, 6 April 1976.......................................................145
Figure 4-29h. Mattituck Inlet, 23 March 1980...................................................145
Figure 4-29i. Mattituck Inlet, 5 April 1993.......................................................146
Figure 4-29j. Mattituck Inlet, 26-30 April 2001................................................146
Figure 4-29k. Mattituck Inlet, 16 April 2003.....................................................147
Figure 4-29l. Mattituck Inlet, 15 April 2004.....................................................147
Figure 4-30. Mining related companies and locations at Mattituck Inlet.........149
Figure 4-31a. Channel elevation, June 1961 (pre-dredging)..............................151
Figure 4-31b. Channel elevation, September 1961 (post-dredging) ..................152
Figure 4-31c. Channel elevation change, June 1961 - September 1961............152
Figure 4-32a. Channel elevation, January 1980 (pre-dredging).........................153
Figure 4-32b. Channel elevation, May 1980 (post-dredging)............................153
Figure 4-32c. Channel elevation change, January 1980 - May 1980.................154
Figure 4-33a. Channel elevation, September 1990 (pre-dredging)....................154
Figure 4-33b. Channel elevation, October 1990 (post-dredging).......................155
Figure 4-33c. Channel elevation change, September 1990 - October 1990.......155
Figure 4-34a. Channel elevation change, May 1980 to August 1983................158
Figure 4-34b. Channel elevation change, May 1980 to June 1985....................158
Figure 4-34c. Channel elevation change, May 1980 to September 1987...........159
Figure 4-34d. Channel elevation change, May 1980 to June 1988....................159
Figure 4-34e. Channel elevation change, May 1980 to October 1989...............160
Figure 4-35. Channel elevation change, October 1990 to January 2002..........161
Figure 4-36. Mattituck Inlet shoreline, pre- and post-dredging,
16 April 2003 and 15 April 2004.................................................162
Figure 4-37a. East bank spit migration, 1941-1976...........................................163
Figure 4-37b. East flood shoal migration, 1976-2003........................................163
Figure 4-38. Mattituck Inlet channel cross sections.........................................164
Figure 4-39a. Mattituck Inlet channel cross-section A......................................165
Figure 4-39b. Mattituck Inlet channel cross-section B ......................................166
Figure 4-39c. Mattituck Inlet channel cross-section C ......................................167
xiii
Figure 4-40a. Boat approaching turn at base of jetties, Mattituck Inlet,
9 July 2004, view looking northwest...........................................167
Figure 4-40b. Boat wake obliquely incident on area of flood shoal
at base of east jetty, Mattituck Inlet, 9 July 2004........................168
Figure 4-41a. Beach profile W1, west of Goldsmith Inlet, March 1998 and
6-8 October 2002.........................................................................169
Figure 4-41b Beach profile W2, west of Goldsmith Inlet, March 1998 and
6-8 October 2002.........................................................................169
Figure 4-41c. Beach profile W4, west of Goldsmith Inlet, March 1998 and
6-8 October 2002.........................................................................170
Figure 4-41d. Beach profile E1, east of Goldsmith Inlet, March 1998 and
6-8 October 2002.........................................................................170
Figure 4-41e. Beach profile E2, east of Goldsmith Inlet, March 1998 and
6-8 October 2002.........................................................................171
Figure 4-41f. Beach profile E3, east of Goldsmith Inlet, March 1998 and
6-8 October 2002.........................................................................171
Figure 4-41g. Beach profile E4, east of Goldsmith Inlet, March 1998 and
6-8 October 2002.........................................................................172
Figure 4-41h. Beach profile E5, east of Goldsmith Inlet, March 1998 and
6-8 October 2002.........................................................................172
Figure 4-41i. Beach profile E6, east of Goldsmith Inlet, March 1998 and
6-8 October 2002.........................................................................173
Figure 4-41j. Beach profile E7, east of Goldsmith Inlet, March 1998 and
6-8 October 2002.........................................................................173
Figure 4-41k. Beach profile E8, east of Goldsmith Inlet, March 1998 and
6-8 October 2002.........................................................................174
Figure 4-42a. Goldsmith Inlet channel entrance, 1938......................................175
Figure 4-42b. Goldsmith Inlet channel entrance, 11 May 1955.........................175
Figure 4-42c. Goldsmith Inlet channel entrance, 1 April 1964..........................176
Figure 4-42d. Goldsmith Inlet channel entrance, 5 October 1966.....................176
Figure 4-42e. Goldsmith Inlet channel entrance, 28 April 1969........................177
Figure 4-42f. Goldsmith Inlet channel entrance, 6 April 1976..........................177
Figure 4-42g. Goldsmith Inlet channel entrance, 24 May 1980.........................178
Figure 4-42h. Goldsmith Inlet channel entrance, 5 April 1993..........................178
Figure 4-42i. Goldsmith Inlet channel entrance, 21 April 1996........................179
Figure 4-42j. Goldsmith Inlet channel entrance, 26-30 April 2001 ..................179
Figure 4-42k. Goldsmith Inlet channel entrance, 16 April 2003........................180
Figure 4-42l. Goldsmith Inlet, 15 April 2004....................................................180
Figure 4-43a. Goldsmith Inlet channel entrance, 1938 and 11 May 1955.........181
xiv
Figure 4-43b. Goldsmith Inlet channel entrance, 11 May 1955,
1 April 1964, and 5 October 1966...............................................182
Figure 4-43c. Goldsmith Inlet channel entrance, 28 April 1969, 28 April
1976, and 24 May 1980...............................................................182
Figure 4-43d. Goldsmith Inlet channel entrance , 21 April 1996 and
5 April 1996.................................................................................184
Figure 4-43e. Goldsmith Inlet channel entrance, 16 April 2002,
16 April 2003, and 15 April 2004................................................184
Figure 4-44a. Goldsmith Inlet channel entrance orientation, 1993-2003 ..........185
Figure 4-44b. Goldsmith Inlet channel entrance orientation, 2002-2004 ..........186
Figure 4-45. Shoaling east of Goldsmith Inlet jetty, 1993-2004......................187
Figure 4-46a. Goldsmith Inlet natural flood shoal, 1938...................................188
Figure 4-46b. Goldsmith Inlet natural flood shoal, 11 May 1955......................188
Figure 4-46c. Goldsmith Inlet -channel with partially intact in-channel flood
shoal, 1 April 1964......................................................................189
Figure 4-46d. Goldsmith Inlet channel, 5 October 1966....................................190
Figure 4-46e. Goldsmith Inlet channel, 28 April 1969......................................190
Figure 4-46f. Goldsmith Inlet channel, 6 April 1976........................................191
Figure 4-46g. Goldsmith Inlet channel, 24 May 1980.......................................191
Figure 4-46h. Goldsmith Inlet channel, 5 April 1993........................................192
Figure 4-46i. Goldsmith Inlet channel, 21 April 1996......................................192
Figure 4-46j. Goldsmith Inlet channel, 16 April 2003......................................193
Figure 4-46k. Goldsmith Inlet channel, 15 April 2004......................................193
Figure 4-47a. Goldsmith Inlet channel center, 11 May 1955 and
1 April 1964.................................................................................195
Figure 4-47b Goldsmith Inlet channel center, 5 October 1966 and
28 April 1969...............................................................................195
Figure 4-47c. Goldsmith Inlet channel center, 6 April 1976 and
24 May 1980................................................................................196
Figure 4-47d. Goldsmith Inlet channel center, 5 April 1993 and
21 April 1996...............................................................................196
Figure 4-47e. Goldsmith Inlet channel center, 16 April 2003 and
15 April 2004...............................................................................197
Figure 4-48a. Goldsmith Inlet flood shoal, 11 May 1955 and 1 April 1964......198
Figure 4-48b. Goldsmith Inlet flood shoal, 5 October 1966 and
6 April 1976.................................................................................198
Figure 4-48c. Goldsmith Inlet flood shoal, 5 April 1993 and 21 April 1996.....199
Figure 4-48d. Goldsmith Inlet flood shoal, 16 April 2003 and 21 April 2004...199
xv
Figure 4-49. Goldsmith Inlet, east bank wetlands, during current
measurement, 8 October 2002.....................................................200
Figure 4-50. Goldsmith Inlet, east bank wetlands, with protective sand bank,
8 October 2002............................................................................201
Figure 4-51. Goldsmith Inlet, east bank wetland, 20 February 2004...............201
Figure 5-1. Regional ADCIRC grid - New York Bight and Long
Island Sound................................................................................205
Figure 5-2. Mattituck Inlet and Mattituck Creek, ADCIRC model
bathymetry...................................................................................205
Figure 5-3. Close view of Mattituck Inlet, ADCIRC model bathymetry.......206
Figure 5-4. NOS stations and 19 September - 8 October 2002 survey tide
gauge locations............................................................................207
Figure 5-5a. Water level at Eaton’s Neck, Huntington Harbor; NOS
measurements and ADCIRC calculations, 19 September -
8 October 2002............................................................................208
Figure 5-5b. Water level at Eaton’s Neck, Huntington Harbor; NOS
measurements and ADCIRC calculations, 5-8 October 2002.....208
Figure 5-5c. Water level at New Haven Harbor, New Haven; NOS
measurements and ADCIRC calculations, 19 September -
8 October 2002............................................................................209
Figure 5-5d. Water level at New Haven Harbor, New Haven; NOS
measurements and ADCIRC calculations, 5-8 October 2002.....209
Figure 5-5e. Water level at Kings Point; NOS measurements and ADCIRC
calculations, 19 September - 8 October 2002..............................210
Figure 5-5f. Water level at Kings Point; NOS measurements and ADCIRC
calculations, 5-8 October 2002....................................................210
Figure 5-6a. Water level at Mattituck Inlet, near west jetty; measurements
and ADCIRC calculations, 19 September - 8 October 2002.......211
Figure 5-6b. Water level at Mattituck Inlet, near west jetty; measurements
and ADCIRC calculations, 5-8 October 2002.............................211
Figure 5-6c. Water level at Mattituck Creek; measurements and ADCIRC
calculations, 19 September - 8 October 2002..............................212
Figure 5-6d. Water level at Mattituck Creek; measurements and ADCIRC
calculations, 5-7 October 2002....................................................212
Figure 5-7. Current velocity at Mattituck Creek; measurements and
ADCIRC calculations, 7-8 October 2002....................................213
Figure 5-8a. Near-maximum flood-tide velocity, Mattituck Inlet offshore
area, 1200 GMT, 7 October 2002................................................214
Figure 5-8b. Near-maximum ebb-tide velocity, Mattituck Inlet offshore
area, 1830 GMT, 7 October 2002................................................214
xvi
Figure 5-8c. Near-maximum flood-tide velocity, Mattituck Inlet ebb shoal
area, 1200 GMT, 7 October 2002................................................215
Figure 5-8d. Near-maximum flood-tide velocity and depth, Mattituck Inlet
offshore shoal area, 1200 GMT, 7 October 2002........................215
Figure 5-8e. Near-maximum ebb-tide velocity, Mattituck Inlet offshore
shoal area, 1830 GMT, 7 October 2002......................................216
Figure 5-8f. Near-maximum ebb-tide velocity and depth, Mattituck Inlet
ebb shoal area, 1830 GMT, 7 October 2002................................216
Figure 5-8g. Flood-current eddies and depth, directly west of Mattituck Inlet,
1200 GMT, 7 October 2002........................................................217
Figure 5-8h. Ebb-current eddies and depth, directly east of Mattituck Inlet,
1830 GMT, 7 October 2002........................................................217
Figure 5-9a. Near-maximum flood-tide velocity, Mattituck Inlet, 1200 GMT,
7 October 2002............................................................................218
Figure 5-9b. Near-maximum flood-tide velocity and depth, Mattituck Inlet,
1200 GMT, 7 October 2002........................................................219
Figure 5-9c. Near-maximum ebb-tide velocity, Mattituck Inlet, 1830 GMT,
7 October 2002............................................................................219
Figure 5-9d. Near-maximum ebb-tide velocity and depth, Mattituck Inlet,
1830 GMT, 7 October 2002........................................................220
Figure 5-10a. Near-maximum flood-tide velocity, Mattituck Inlet flood shoal
area, 1200 GMT, 7 October 2002................................................220
Figure 5-10b. Near-maximum flood-tide velocity and depth, Mattituck Inlet
flood shoal area, 1200 GMT, 7 October 2002.............................221
Figure 5-10c. Near-maximum ebb tide velocity, Mattituck Inlet flood shoal area,
1830 GMT, 7 October 2002........................................................221
Figure 5-10d. Near-maximum ebb-tide velocity and depth, Mattituck Inlet
flood shoal area, 1830 GMT, 7 October 2002.............................222
Figure 5-11a. Near-maximum flood-tide velocity, Mattituck Inlet,
pre-dredging grid.........................................................................223
Figure 5-11b. Near-maximum flood-tide velocity, Mattituck Inlet,
post-dredging grid .......................................................................223
Figure 5-11c. Near-maximum ebb-tide velocity, Mattituck Inlet,
pre-dredging grid.........................................................................224
Figure 5-11d. Near-maximum ebb tide velocity, Mattituck Inlet,
post-dredging grid .......................................................................224
Figure 5-11e. Near-maximum flood-tide velocity and depth, Mattituck Inlet
pre-dredging grid.........................................................................225
Figure 5-11f. Near-maximum flood-tide velocity and depth, Mattituck Inlet
post-dredging grid .......................................................................225
Figure 5-12. Comparative current velocity plot locations................................226
xvii
Figure 5-13a. Current velocity directly north of Mattituck Inlet east bank
flood shoal, pre-dredging and synthetic post-dredging condition
(Location A)................................................................................226
Figure 5-13b. Current velocity directly north of Mattituck Inlet east bank
flood shoal, pre-dredging and synthetic post-dredging condition
(Location B) ................................................................................227
Figure 5-13c. Current velocity directly north of Mattituck Inlet east bank
flood shoal, pre-dredging and synthetic post-dredging condition
(Location C) ................................................................................227
Figure 5-14a. Mattituck Inlet natural state, near-maximum offshore spring
flood-tide velocity, 1200 on 7 October 2002...............................229
Figure 5-14b. Mattituck Inlet natural state, near-maximum offshore spring
flood-tide velocity, 1200 on 7 October 2002...............................229
Figure 5-14c. Mattituck Inlet natural state, offshore and inlet spring flood-tide
velocity, 1230 on 7 October 2002 ...............................................230
Figure 5-14d. Mattituck Inlet natural state, offshore spring flood-tide and near-
maximum inlet spring flood-tide velocity,
1430 on 7 October 2002..............................................................230
Figure 5-14e. Mattituck Inlet natural state, offshore spring ebb-tide and inlet
spring flood-tide velocity, 1530 on 7 October 2002....................231
Figure 5-14f. Mattituck Inlet natural state, near maximum offshore spring
ebb-tide and inlet spring ebb-tide velocity, 1830 on
7 October 2002............................................................................231
Figure 5-14g. Mattituck Inlet natural state, offshore spring ebb-tide and inlet near
maximum spring ebb-tide velocity, 2100 on 7 October 2002.....232
Figure 5-14h. Mattituck Inlet natural state, offshore spring flood-tide and inlet
spring ebb-tide velocity, 2200 on 7 October 2002......................232
Figure 5-14i. Mattituck Inlet natural state, near maximum offshore spring
flood tide and inlet spring ebb-tide velocity, 0030 on 8 October
2002.............................................................................................233
Figure 5-15. Mattituck Inlet assumed (synthetic) natural state and offshore
water level and current velocity comparison locations ...............233
Figure 5-16a. Mattituck Inlet natural state and offshore water level
comparison (Locations A and B).................................................234
Figure 5-16b. Mattituck Inlet natural state and offshore water level
comparison (Locations A and C).................................................234
Figure 5-16c. Mattituck Inlet natural state and offshore water level
comparison (Locations A and D) ................................................235
Figure 5-17a. Mattituck Inlet natural state and offshore current velocity
comparison (Locations A and B).................................................235
Figure 5-17b. Mattituck Inlet natural state and offshore current velocity
comparison (Locations A and C).................................................236
xviii
Figure 5-17c. Mattituck Inlet natural state and offshore current velocity
comparison (Locations A and D) ................................................236
Figure 5-18a. Near-maximum offshore flood-tide velocity, Mattituck Inlet
offshore shoal area, 1200 GMT on 7 October 2002....................237
Figure 5-18b. Near-maximum offshore flood-tide velocity and depth, Mattituck
Inlet offshore shoal area, 1200 GMT on 7 October.....................238
Figure 5-18c. Near-maximum inlet flood-tide velocity, Mattituck Inlet
offshore shoal area, 1430 GMT on 7 October 2002....................238
Figure 5-18d. Near-maximum inlet flood-tide velocity and depth, Mattituck
Inlet offshore shoal area, 1430 GMT on 7 October.....................239
Figure 5-18e. Near-maximum offshore ebb-tide velocity, Mattituck Inlet offshore
shoal area, 1830 GMT on 7 October 2002 ..................................239
Figure 5-18f. Near-maximum offshore ebb-tide velocity and depth, Mattituck
Inlet offshore shoal area, 1830 GMT on 7 October.....................240
Figure 5-18g. Near-maximum inlet ebb-tide velocity, Mattituck Inlet offshore
shoal area, 2030 GMT on 7 October 2002 ..................................241
Figure 5-18h. Near-maximum inlet ebb-tide velocity and depth, Mattituck Inlet
offshore shoal area, 2030 GMT on 7 October 2002....................241
Figure 5-19. Current velocity comparison plot locations.................................242
Figure 5-20a. Current velocity at Mattituck Inlet entrance
(Locations A and B) ....................................................................242
Figure 5-20b. Current velocity between Mattituck Inlet entrance and offshore
shoal (Locations C through E).....................................................243
Figure 5-21. DYNLET grid of Goldsmith Inlet, with nodes and extents of
nodal cross sections.....................................................................244
Figure 5-22a. Water-level measurements offshore of Goldsmith Inlet and
Node 2 calculations, 20 September - 8 October 2002.................246
Figure 5-22b. Water-level measurements offshore of Goldsmith Inlet and
Node 2 calculations, 5-8 October 2002.......................................246
Figure 5-22c. Water-level measurements at Goldsmith Pond and DYNLET
Node 30 calculations, 20 September - 8 October 2002...............247
Figure 5-22d. Water-level measurement offshore of Goldsmith Pond and
DYNLET Node 30 calculations, 5-8 October 2002 ....................247
Figure 5-23a. Current velocity measurement and calculated velocities at
Nodes 13 and 14, 7-8 October 2002............................................248
Figure 5-23b. Current velocity measurement and Nodes 13 and 14 calculations,
8 October 2002............................................................................248
Figure 5-24a. Water-level measurements offshore of Goldsmith Inlet and
DYNLET Nodes 5 and 8 calculations, 5-8 October 2002...........250
Figure 5-24b. Water-level measurements offshore of Goldsmith Inlet and
DYNLET Nodes 8 and 9 calculations, 5-8 October 2002...........251
xix
Figure 5-24c. Water-level measurements offshore of Goldsmith Inlet and
DYNLET Nodes 9 and 10 calculations, 5-8 October 2002.........251
Figure 5-24d. Water-level measurements offshore of Goldsmith Inlet and
DYNLET Nodes 10 and 15 calculations, 5-8 October 2002.......252
Figure 5-24e. Water-level measurements offshore of Goldsmith Inlet and
DYNLET Nodes 15 and 20 calculations, 5-8 October 2002.......252
Figure 5-24f. Water-level measurements offshore of Goldsmith Inlet and
DYNLET Nodes 20 and 30 calculations, 5-8 October 2002.......253
Figure 5-25a. Discharge at Goldsmith Inlet, DYNLET Nodes 5 and 8
calculations, 5-8 October 2002....................................................253
Figure 5-25b. Discharge at Goldsmith Inlet, DYNLET Nodes 9 and 10
calculations, 5-8 October 2002....................................................254
Figure 5-25c. Discharge at Goldsmith Inlet, DYNLET Nodes 15 and 20
calculations, 5-8 October 2002....................................................254
Figure 5-26a. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 6 and 7 calculations, 5-8 October 2002...........255
Figure 5-26b. Current velocity calculations offshore of Goldsmith Inlet and
DYNLET Nodes 7 and 8 calculations, 5-8 October 2002...........256
Figure 5-26c. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 8 and 9 calculations, 5-8 October 2002...........256
Figure 5-26d. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 9 and 10 calculations, 5-8 October 2002.........257
Figure 5-26e. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 10 and 11 calculations, 5-8 October 2002.......257
Figure 5-26f. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 11 and 13 calculations, 5-8 October 2002.......258
Figure 5-26g. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 13 and 16 calculations, 5-8 October 2002.......258
Figure 5-26h. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 16 and 17 calculations, 5-8 October 2002.......259
Figure 5-26i. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 17 and 21 calculations, 5-8 October 2002.......259
Figure 5-26j. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 21 and 22 calculations, 5-8 October 2002.......260
Figure 5-26k. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 22 and 30 calculations, 5-8 October 2002.......260
Figure 5-27. Maximum calculated flood- and ebb-spring-tide current velocities
and channel elevation at Goldsmith Inlet, 7 October 2002 .........261
Figure 5-28a. Goldsmith Inlet spring flood-tide maximum current velocity,
total calculation domain...............................................................262
xx
Figure 5-28b. Goldsmith Inlet spring ebb-tide maximum current velocity,
total calculation domain...............................................................262
Figure 5-28c. Goldsmith Inlet spring flood-tide maximum current velocity,
inlet channel.................................................................................263
Figure 5-28d. Goldsmith Inlet spring ebb-tide maximum current velocity,
inlet channel ................................................................................263
Figure 5-28e. Goldsmith Inlet spring flood-tide and ebb-tide maximum
current velocity difference...........................................................264
Figure 6-1. Classification of tidal inlet morphology......................................266
Figure 6-2. Tidal prism-channel area relation, Mattituck Inlet and Atlantic
coast dual jettied inlets................................................................273
Figure 6-3. Mattituck Inlet offshore water-level measurements and
calculations by CEA model.........................................................273
Figure 6-4. Mattituck Creek water-level measurements and calculations
by CEA model.............................................................................274
Figure 6-5. Escoffier curve calculated for Mattituck Inlet, CEA model........275
Figure 6-6. Shoaling at Mattituck Inlet and Mattituck Creek,
6-8 October 2002.........................................................................277
Figure 6-7. Goldsmith Pond water-level measurements and calculations
by CEA model.............................................................................280
Figure 6-8. Escoffier curve calculated for Goldsmith Inlet, CEA model ........281
Figure 6-9. Tidal prism-channel area relations, Goldsmith Inlet, Chesapeake
Bay small inlets, and Puget Sound inlets ......................................281
Figure 6-10 Shoaling at Goldsmith Inlet and Goldsmith Pond,
8 October 2002..............................................................................283
Figure 6-11. Comparison of channel cross section and tidal prism relations ....285
List of Tables
Table 2-1. Selected Tide Ranges for Long Island Sound ................................... 16
Table 2-2. Average Wind Direction for Long Island Sound................................16
Table 2-3. Calculated Significant Wave Height and Period................................17
Table 2-4. Mean and Maximum Measured Current Velocities for Long Island
Sound..................................................................................................18
Table 2-5. Mattituck Inlet Dredging History.......................................................24
xxi
Table 2-6. Mattituck Inlet Maintenance History..................................................24
Table 2-7. Summary of Federal Commercial Sand Mining Permits....................25
Table 2-8. Mattituck Park District Permit Mining Volume Estimates
1960-1975...........................................................................................25
Table 2-9. Goldsmith Inlet Dredging History......................................................41
Table 3-1. Phi Units and Millimeter Equivalents ................................................69
Table 3-2. Grain-Size Analysis, Mattituck Inlet Offshore Area,
Profiles 56 and 57...............................................................................73
Table 3-3. Grain-Size Analysis, Goldsmith Inlet Offshore Area,
Profiles 59 and 60...............................................................................99
Table 4-1. Estimated Offshore Volume Change, Mattituck Inlet, 1927-2002...114
Table 4-2. Mattituck Inlet Flood Shoal Area 1935-1938...................................124
Table 4-3. Estimated Mattituck Inlet Flood Shoal Volumes and Areas,
1935-1938.........................................................................................125
Table 4-4. Calculated Versus Measured Dredging Volumes, Mattituck Inlet
Channel.............................................................................................156
Table 4-5. Estimated Sediment Accumulation Rates, Mattituck Inlet Federal
Navigation Channel..........................................................................157
Table 4-6. Summary of Morphology Change at Goldsmith Inlet, 1955
to Present..........................................................................................202
Table 5-1. Goldsmith Inlet DYNLET Node Depths..........................................249
Table 6-1. Inlet Bypassing and Channel Cross-Sectional Stability
Classification of Inlets......................................................................267
Table 6-2. Tidal Prism and Minimum Channel Cross-Sectional Area
Relationships....................................................................................268
Table 6-3. Mattituck Inlet r Ratio and Associated Physical Quantities.............272
Table 6-4. Channel Equilibrium Area Model Quantities for Mattituck Inlet ....274
Table 6-5. Goldsmith Inlet r Ratio and Associated Physical Quantities............279
Table 6-6. Channel Equilibrium Area Information for Goldsmith Inlet............279
Table 6-7. Goldsmith Inlet Flood Shoal and Physical Quantities......................284
Table 7-1. Mattituck Inlet and Goldsmith Inlet – Morphologic
Characteristics..................................................................................287
Table 7-2. Mattituck Inlet and Goldsmith Inlet, Nearshore Slopes and Sediment
Grain Size.........................................................................................287
Table 7-3. Mattituck Inlet and Goldsmith Inlet – Hydrodynamic
Characteristics..................................................................................288
Table 7-4. Mattituck Inlet and Goldsmith Inlet, Summary of Key Engineering
Activities ..........................................................................................288
xxii
Preface
This study of the morphology and dynamics of Mattituck Inlet and
Goldsmith Inlet, NY, was conducted at the U.S. Army Engineer Research and
Development Center (ERDC), Coastal and Hydraulics Laboratory (CHL),
Vicksburg, MS, and the Department of Geography, Hunter College, City
University of New York (CUNY). Work was performed as an activity of the
Coastal Morphology Modeling and Channel Evolution Work Unit of the Coastal
Inlets Research Program (CIRP) administered at CHL under the Navigation
Systems Program for Headquarters, U.S. Army Corps of Engineers
(HQUSACE). Mr. Barry W. Holliday is HQUSACE lead technical monitor for
CIRP. Dr. Sandra K. Knight is Technical Director for the Navigation Systems
Program, and Dr. Nicholas C. Kraus, Senior Scientists Group (SSG), CHL, is
CIRP Program Manager and Principal Investigator of the Coastal Morphology
Modeling and Channel Evolution Work Unit.
CIRP conducts applied research to improve USACE capability to manage
federally maintained inlets on all coasts of the United States, covering the
Atlantic Ocean, Gulf of Mexico, Pacific Ocean, and Great Lakes, as well as other
areas of responsibility of USACE. CIRP objectives are to improve understanding
and develop predictive technology for (a) design, maintenance, and operation of
inlet navigation projects, in particular, to reduce the cost of maintenance
dredging, and (b) preservation of the beaches adjacent to inlets in a systems
approach that treats the inlet and beaches as a sediment-sharing system. To
achieve these objectives, CIRP is organized in work units that conduct research
and development in hydrodynamic, sediment transport, and morphology change
modeling; navigation channel performance; sediment bypassing and adjacent
beaches; jetty performance; scour at jetties; laboratory and field investigations;
and technology transfer.
This report was written by Mr. Michael J. Morgan, graduate student, Hunter
College, CUNY, Dr. Kraus, and Ms. Jodi M. McDonald, U.S. Army Engineer
District, New York. Ms. McDonald was formerly in the New York District
Operations Division (OD), and is presently in the Plan Formulation Branch,
Planning Division. The September and October 2002 data collection was
performed under contract with Offshore and Coastal Technologies, Inc. (OCTI),
Chadds Ford, PA. Mr. William G. Grosskopf, OCTI, led the data-collection
effort and provided additional information in support of this study. Dr. Mark R.
Byrnes, Applied Coastal Research and Science, Inc., supplied and provided
information on various geospatial data sets and related metadata. Geographic
Information System support was provided by Ms. Mary Claire Allison, Coastal
Engineering Branch, CHL, and assistance in hydrodynamic modeling by
Mr. Mitchell E. Brown, SSG. Dr. Brian K. Batten, Coastal Engineering Branch,
xxiii
CHL, provided valuable information and discussion at the final stage of this
study. Logistical support at Hunter College was provided by Dr. Jeffrey Osleeb,
executive officer, Ph.D. Program in Earth and Environmental Sciences, CUNY.
Mr. John F. Tavolaro, Acting Chief, OD, New York District, and Ms. Lynn M.
Bocamazo, Engineering Division, New York District, provided bathymetric
survey data and engineering and coastal processes information for Mattituck
Inlet. Mr. James Richter, Town Engineer, Town of Southold, NY, provided
information on dredging and coastal processes at Goldsmith Inlet. Messrs. Barry
Pendergrass, New York State Department of State, Division of Coastal
Resources, and Richard Tuers, New York State Department of Environmental
Conservation, furnished copies of reports and aerial photographs. Dr. DeWitt
Davies, Suffolk County Department of Planning organized a review meeting for
the working draft of this report that resulted in many valuable suggestions and
corrections by local and state government officials. The meeting was attended
by: Dr. Davies, Mr. Thomas Isles, Ms. Lauretta Fischer, and Mr. Ronald
Verbarg of the Suffolk County Department of Planning; Mr. William Shannon
and Mr. Thomas Rogers of the Suffolk County Department of Public Works;
Dr. Henry Bokuniewicz of the Marine Sciences Research Center at the State
University of New York, Stony Brook; Mr. Jay Tanski of New York Sea Grant;
Messrs. George Hamarth and Richard Tuers of the New York State Department
of Environmental Protection; and Mr. Barry Pendergrass of the New York State
Department of State.
Work at CHL was performed under the general administrative supervision of
Mr. Thomas W. Richardson, Director, and Dr. William D. Martin, Deputy
Director, respectively, CHL. Final report formatting was completed by
Ms. J. Holley Messing, Coastal Engineering Branch, CHL.
At the time of publication of this report, Dr. James R. Houston was Director
of ERDC, and COL James R. Rowan, EN, was Commander and Executive
Director.
xxiv
Conversion Factors: Non-SI to
SI Units of Measurement
Non-SI units of measurement appearing in this report can be converted to SI
units as follows:
Multiply By To Obtain
cubic yards 0.7645549 cubic meters
feet 0.3048 meters
miles (U.S. statute) 1.609347 kilometers
square feet 0.09290304 square meters
square yards 0.8361274 square meters
yards 0.9144 meters
1 Introduction
Coastal inlets are narrow waterways that connect a bay, lagoon, or similar water body
with a larger water body that generates motion between them, such as forced by the tide
in the oceans and by seiching in the Great Lakes. Inlets serve commercial, military, and
recreational functions. They are also central to the health of marine and coastal terrestrial
organisms by allowing water exchange and by being a conduit for movement of
organisms and nutrients between the sea and estuaries or bays. Consequently, inlets have
been the subject of considerable research in coastal engineering and science.
In the present study, motivation for improved understanding of inlet processes lies in
reducing the cost of maintaining navigable channels and more reliably predicting the
functioning of proposed inlet modifications. Related concerns are the influence of an
inlet or planned inlet modification on the adjacent beaches and the associated ecosystem.
The overall aim of an inlet maintenance program is to establish and sustain a dynamic
state of equilibrium for the inlet morphology with minimal adjustment required of the
adjacent beaches and minimal change to the ebb- and flood-tidal shoals.
Background
The physical environment of a tidal inlet is determined by the forcing of the
periodically reversing tidal current, and by waves, wave-induced currents, wind-induced
currents, and storms. The interaction includes the type of sediment (grain size) and
sediment transport, and the morphologic response of the inlet to the hydrodynamic
forcing, which then feed back to the hydrodynamics. Two types of inlet stability are
commonly recognized, one referring to locational stability and orientation of the inlet
channel or gorge, and the other to stability of the inlet channel cross-sectional area. The
stability of an inlet depends on the balance between two physical processes, the wave-
induced longshore current that transports sediment toward the inlet, creating a tendency
towards closure and migration, and the tidal flow within the inlet that tends to scour the
bottom and banks of the channel, removing sediment from the inlet throat (Johnson 1919;
Bruun and Gerritsen 1959).
Most field and theoretical studies of inlet stability have concerned large tidal inlets
with sand-sized sediment, as commonly found on all coasts of the United States. Such
inlets are prevalent and have great economic and environmental functions. However,
coastal inlets are also found on rocky coasts, and small inlets that tend to close are of
environmental concern (Goodwin 1996). Although inlet channel cross-sectional area has
been investigated (e.g., Le Conte 1905; O’Brien 1931, 1969; Jarrett 1976; Byrne et al.
1980; Moody 1988; Hume and Merdendorf (1990); Kraus 1998; Hughes 2002), the role
of sediment size in the stability of inlets has received almost no investigation (Simpson
Chapter 1 Introduction 1
1976). The present study attempts to contribute to understanding of small inlets and the
role of grain size by examining two relatively small inlets on a mixed sediment coast that
includes gravel.
Inlets along the south shore of Long Island, NY, have received substantial study
owing to their easy access and proximity to the New York metropolitan area. On the
south shore, there are presently six federally maintained permanent inlets (from west to
east: Rockaway Inlet, East Rockaway Inlet, Jones Inlet, Fire Island Inlet, Moriches Inlet,
and Shinnecock Inlet), and they serve long and broad bays surrounded by towns and
commercial entities. Of the large literature on Long Island south shore inlets,
representative examples are:
a. Geomorphology, sedimentology, and sediment budgets: Taney (1961), Kumar
and Sanders (1974), Leatherman and Allen (1985), Leatherman (1989), Kana
(1995), Morang et al. (1999), Schwaab et al. (1999).
b. Coastal and inlet processes: Panuzio (1968), Tanski et al. (1990), Militello et al.
(2000).
c. Site-specific inlet studies: Gofseyeff (1952), Czerniak (1977), Schmeltz et al.
(1982), Militello and Kraus (2001), Kraus et al. (2003).
Inlets along the south shore of Long Island have been dynamic, both in location and
channel cross section, as documented in many of the these references.
In contrast to south shore inlets of Long Island, inlets on the north shore have
received little study. Many of these inlets are small and serve small and isolated water
bodies. Significantly, north shore inlets appear to be more stable in location than the
south shore inlets.1 Why are these inlets more stable and, apparently, longer lived, as
compared to the south shore inlets?
Although glacial processes dominate the surficial sediments and geologic structure of
Long Island, the sediment along the south shore consists predominantly of fine to
medium sand, with a median grain size of 0.3 mm being typical. In contrast to the sandy
beaches backed by dunes found along the south shore of Long Island, high bluffs and a
wide range in grain size, with gravel and cobble common, characterize its north shore.
The tide range along the north shore is about double that of the south shore. Longshore
sediment transport is an order of magnitude less on the north shore as compared to the
south shore, and the waves along the north shore are steeper. The inner shelf on the north
shore is steeper than along the south shore.
1 The World Wide Web site http://www.ilovelbny.com/LongBeachMaps.html displays several historic maps
of East Rockaway Inlet, Jones Inlet, and several ephemeral inlets on the western end of the south shore of
Long Island. These maps clearly indicate inlet opening, closing, and significant migration of the westernmost
inlets from the first map, dated 1797. Sometimes the easternmost inlets are absent (closed). The names of
the inlets may be different, and inlets with other names and that no longer exist can also be seen.
2 Chapter 1 Introduction
Chapter 1 Introduction 3
It appears that much can be learned about inlet stability through study of the
inlets of the north shore of Long Island because of the substantial difference in
coastal environment as compared to the south shore and to most inlets on sandy
coasts in general.
Study Site
The inlets investigated in this study, Mattituck Inlet and Goldsmith Inlet, are
located 5.2 miles apart on the eastern end of the north shore of Long Island, NY.
Inlets of varying size are found along the south and north shores, as well as in the
bays of Long Island. Inlets on the north shore of Long Island have received little
study, with the exception of Stony Brook Harbor (Cooke 1985; Park 1985;
Zarillo and Park 1987). The inlets of Long Island’s north shore vary greatly in
size and configuration, from large ones, such as Port Jefferson Harbor and Oyster
Bay, to small inlets such as Mattituck Inlet and Goldsmith Inlet (Figure 1-1).
Port Jefferson Harbor and the entrance to Oyster Bay are of comparable scale to
the more extensively studied inlets of the south shore, but their bay systems are
much smaller.
Mattituck Inlet and Goldsmith Inlet are connected to Long Island Sound.
Long Island Sound is a semienclosed tide-dominated water body that
communicates with the Atlantic Ocean at both its eastern and western ends, via
Block Island Sound and the East River (and ultimately, New York Harbor)
respectively. The relatively large mean tide (5.2 ft)1 and spring tide range (6.0 ft)
along the Eastern Long Island Sound is one controlling factor for the stability of
both inlets (Figures 1-2 and 1-3).
Mattituck Inlet is a federally maintained channel and connects Long Island
Sound to Mattituck Creek (Figure 1-4). Mattituck Inlet is the only major harbor
on the north fork of Long Island and is a commercial and recreational boating
center. Two jetties stabilize this inlet, and the navigation channel is maintained
to a depth of 7 ft mean low water (mlw) with a 2-ft allowable overdraft.
Overdraft refers to the contractually allowable depth of dredging greater than the
authorized depth to account for equipment limitations and survey accuracy. The
inlet was sometimes dredged from the mid 1920s to mid 1970s for local
commercial mineral operations (sand and gravel mining). The tidal prism, the
volume of water entering or exiting an inlet during a flood or ebb tide, is a
primary control on inlet stability and channel cross-sectional area. The present
study calculates a tidal prism of 4.32 ×107 cu ft at Mattituck Inlet based on
measured bay area and spring tide range.
1 Engineering activities such as surveying and dredging, as well as historic documentation of tide
ranges associated with this study are reported in their original units, U.S. Customary (non-SI) units.
As an aid to those ongoing activities and to maintain continuity with previous publications
employing non-SI units, those units are preserved in the present context. Oceanographic quantities
are expressed in SI units. A table for converting non-SI to SI units is given on page xxiv.
R
o
c
k
a
w
a
y
I
n
l
e
t
E
a
s
t
R
o
c
k
a
w
a
y
I
n
l
e
t
S
h
i
n
n
e
c
o
c
k
I
n
l
e
t
G
r
e
a
t
P
e
c
o
n
i
c
B
a
y
F
i
r
e
I
s
l
a
n
d
I
n
l
e
t
J
o
n
e
s
I
n
l
e
t
M
o
r
i
c
h
e
s
I
n
l
e
t
G r e a t S o u t h B a y
G
o
l
d
s
m
i
t
h
I
n
l
e
t
M
a
t
t
i
t
u
c
k
I
n
l
e
t
G
l
e
n
C
o
v
e
O
y
s
t
e
r
B
a
y
S
t
o
n
y
B
r
o
o
k
H
a
r
b
o
r
P
o
r
t
J
e
f
f
e
r
s
o
n
Lo
n
g
I
s
l
a
n
d
,
N
e
w
Y
o
r
k
L
o
n
g
I
s
l
a
n
d
S
o
u
n
d
Mo
n
t
a
u
k
P
o
i
n
t
Or
i
e
n
t
P
o
i
n
t
o
c
k
a
w
a
y
I
n
l
e
t
E
a
s
t
R
o
c
k
a
w
a
y
I
n
l
e
t
S
h
i
n
n
e
c
o
c
k
I
n
l
e
t
G
r
e
a
t
P
e
c
o
n
i
c
B
a
y
F
i
r
e
I
s
l
a
n
d
I
n
l
e
t
J
o
n
e
s
I
n
l
e
t
M
o
r
i
c
h
e
s
I
n
l
e
t
G r e a t S o u t h B a y
R
G
o
l
d
s
m
i
t
h
I
n
l
e
t
M
a
t
t
i
t
u
c
k
I
n
l
e
t
G
l
e
n
C
o
v
e
O
y
s
t
e
r
B
a
y
S
t
o
n
y
B
r
o
o
k
H
a
r
b
o
r
P
o
r
t
J
e
f
f
e
r
s
o
n
Lo
n
g
I
s
l
a
n
d
,
N
e
w
Y
o
r
k
L
o
n
g
I
s
l
a
n
d
S
o
u
n
d
Mo
n
t
a
u
k
P
o
i
n
t
Or
i
e
n
t
P
o
i
n
t
T
h
e
R
a
c
e
Fi
g
u
r
e
1
-
1
.
L
o
n
g
I
s
l
a
n
d
,
N
Y
,
a
n
d
s
e
l
e
c
t
e
d
i
n
l
e
t
s
a
n
d
h
a
r
b
o
r
s
4 Chapter 1 Introduction
E a s t Roc k a way I n l e t Shi nnecoc k I nl et
F i r e I s l a n d I n l e t
J o n e s I n l e t Mo r i c h e s I n l e t
Long Island, New York
Long Island Sound
Montauk Point
Orient Point
R o c k a w a y I n l e t
Mattituck Inlet
Go l d s mit h I n l e t
E a s t R o c k a w a y I n l e t Shi nnecoc k I nl et
F i r e I s l a n d I n l e t
J o n e s I n l e t Mo r i c h e s I n l e t
Long Island, New York
Long Island Sound
Montauk Point
Orient Point
R o c k a w a y I n l e t
Mattituck Inlet
Go l d s mit h I n l e t
Figure 1-2. Long Island, NY, with study area inset
Mattituck Inlet
Mattituck Creek
Goldsmith PondGoldsmith Inlet
Figure 1-3. Study area with Mattituck Inlet and Goldsmith Inlet insets
Chapter 1 Introduction 5
Figure 1-4. Mattituck Inlet and Mattituck Creek, 16 April 2003
Goldsmith Inlet (Figure 1-5) is much smaller than Mattituck Inlet and is maintained
as needed by the Town of Southold (and, in the past, by Suffolk County). It has been
occasionally dredged as a source of sand and gravel for upland activities and to provide
sediment for renourishment of Kenneys Road Beach, located east and downdrift of the
inlet. In recent times, Goldsmith Inlet has been dredged on an emergency basis, when the
inlet has experienced closure, with the dredged material placed on the downdrift (eastern)
adjacent beach. Goldsmith Inlet received an emergency dredging in the winter of 2001
and in March 2004.
Goldsmith Inlet connects Long Island Sound to Goldsmith Pond. The inlet has a
nonfunctional jetty on its west side and is non-navigable, with typical depths ranging
from 0.5 to 3 ft NAVD88. The present study calculated a tidal prism of 3.04 x 106 cu ft
at Goldsmith Inlet, 14 times smaller than that of Mattituck Inlet based on pond area and
measured spring tide range.
Previous Studies
A small number of coastal processes studies and shoreline change analysis reports are
available for the eastern end of the north shore of Long Island. Few studies have been
made of north shore inlets, with the exception of Stony Brook Harbor (Cooke 1985; Park
1985; Zarillo and Park 1987), which lies about 37.5 miles west of the Mattituck Inlet.
The literature pertaining to this area is reviewed here.
6 Chapter 1 Introduction
Figure 1-5. Goldsmith Inlet and Goldsmith Pond, 16 April 2003
The U.S. Army Engineer District, New York, quantified beach recession and
accretion and storm-related damage for the north shore of Long Island in Suffolk County
in 1969. The New York District issued an update of this report in 1996. This report
notes the high rate of bluff erosion for the areas directly adjacent to Mattituck Inlet and
the area east of Goldsmith Inlet as a primary issue. The New York District (1969) report
estimates a recession rate of approximately 1 ft/year for these areas and classified erosion
as moderate. Erosion of the area directly east of Mattituck Inlet was identified as a
concern. The report also identified beach erosion as the primary concern for the areas
west of Goldsmith Inlet and classified erosion for the Kenneys Road Beach area as
severe.
In 1987, The New York State Department of Environmental Conservation
(NYSDEC) conducted a coastal erosion reconnaissance study of the shoreline from Duck
Pond Point (approximately 16,000 ft west of Goldsmith Inlet) to Horton Point
(approximately 16,000 ft east of Goldsmith Inlet) (Figure 1-6). The NYSDEC report
reaches similar conclusions as the New York District (1969) report and notes the
influence of Goldsmith jetty and a series of privately installed groins on the shoreline,
where accretion on the west side and erosion on the east side is observed.
Chapter 1 Introduction 7
Goldsmith Inlet
H o r t o n P o i n t
D u c k P o n d P o i n t
Goldsmith Inlet
H o r t o n P o i n t
D u c k P o n d P o i n t
Figure 1-6. Shoreline from Duck Pond Point to Horton Point
Davies et al. (1971) and Davies (1972) studied erosion of the north shore of Long
Island, and Offshore and Coastal Technologies, Inc. (OCTI 1998) surveyed the shoreline
and beach profile from the Southold town line to Horton Point. Fields et al. (1999)
conducted a historical shoreline change analysis for the same area. In these studies, the
observed rates of erosion were attributed to the lack of sediment supply, storms, and the
impoundment of sediment by jetties and other coastal structures. Omholt (1974)
conducted a study of the effects of small groins on the shorelines of the north shore of
Long Island. Schubel (1976) studied the consequence of commercial mining operations,
conducted on the beach directly west of Mattituck Inlet. Alpine Ocean Seismic Survey,
Inc. (1998) conducted a geophysical investigation of the offshore area from Duck Pon
Point to Horton Point in 1998. Greenman-Pedersen Associates, P.C. (1981) studied the
response of the adjacent east shoreline to the Goldsmith Inlet jetty through analysis of
historic aerial photography. The report concluded that the Goldsmith Inlet jetty and a
private groin located 3,400 ft east of the jetty were responsible for significant downdrift
erosion from 1964 to 1978.
An Erosion Management Plan for the Town of Southold was prepared in 1995 (Allee
King Rosen and Fleming, Inc. et al. 1995). In 1996, the Town of Southold conducted a
workshop examining erosion between Duck Pond Point and Horton Point. One result of
this workshop was a set of recommendations by Leatherman (1996)1 that included
1 Leatherman, S. P. (1996). “Workshop observations and recommendatons,” in report of the workshop
examining erosion of the coastal barrier landform between Duck Pond Point and Horton, Town of Southold,
8 Chapter 1 Introduction
shortening of the Goldsmith Inlet jetty to half its length and installation of groins at
selected locations downdrift of the inlet. Although the stability of Goldsmith Inlet was
not explicitly addressed, its possible closure and the resulting environmental and water
quality problems were considered in the recommendations.
Contemporaneously with the present study, in support of the New York District,
Batten and Kraus (2005) performed a Section 111 analysis for the downdrift (east) shore
at Mattituck Inlet. Section 111 of the River and Harbor Act of 1968 authorizes studies
for the prevention or mitigation of shore damages attributable to Federal navigation
works. Batten and Kraus (2005) analyzed shoreline change both updrift and downdrift of
Mattituck Inlet in a regional context, including development of a sediment budget for the
coastal area adjacent to the inlet.
Motivation
Inlet properties of bay size, tide range, wave height, sediment size, and location on a
wave-sheltered or unsheltered coast have been found to influence the stability relation
between inlet tidal prism and cross-sectional area. These and other processes, such as
potential geologic controls and wave steepness, can be investigated at Mattituck Inlet and
Goldsmith Inlet. The apparent longevity and locational stability of Mattituck Inlet and
Goldsmith Inlet, as compared to much larger inlets on the south shore of Long Island
warrants attention. Why should such relatively small inlets be so stable?
Small inlets offer a convenient opportunity to investigate inlet morphodynamics
because of their limited size and greater accessibility. Byrne et al. (1980) found that the
relationship between changes in inlet cross-sectional area and flow regime differed for
small inlets. Through the analysis of width-to-depth ratios found at both small and large
inlets, they concluded that small inlets must be more hydraulically efficient than large
inlets to maintain stability. Goldsmith Inlet is similar in size to those studied by Byrne et
al. (1980), whereas Mattituck Inlet is larger, but yet small as compared to the 108 inlets
analyzed by Jarrett (1976) in developing predictive relationships for inlet channel cross-
sectional area.
The close proximity of these inlets, one a federally maintained inlet (Mattituck Inlet),
and the other a seminatural inlet (Goldsmith Inlet), provides an opportunity to examine
the dynamics and stability of small inlets in an engineered condition and an almost
natural condition, respectively. Although they share the same wave climate and the same
tidal forcing, the differences in tidal prism and number of jetties benefit a comparative
study of inlet stability. Mattituck Inlet is dredged for navigation, is stabilized by two
jetties, and has a channel composed predominantly of sand and gravel-sized sediment.
Goldsmith Inlet is dredged infrequently, is shallow and non-navigable, has one jetty that
is fully impounded, and is substantially armored by gravel (Figure 1-7).
NY, Appendix II-A1, unpublished report.
Chapter 1 Introduction 9
Study Objective
The stability in location and in cross-sectional channel area of coastal inlets is of
central interest for the operation and maintenance of navigation channels, as well as for
understanding the interaction of inlets and beaches. The control of coarse sediment
(gravel) on inlet morphology and hydrodynamics is also of scientific and engineering
interest. In an effort to improve understanding of tidal inlet stability, this study was
undertaken at two Long Island, NY, north shore inlets, Mattituck Inlet and Goldsmith
Inlet.
The study covers review of the literature, compilation and analysis of historic New
York District survey records, site visits, short-term measurements of water level and
current, bathymetric surveys, sediment sampling, bathymetry change and aerial
photography analysis, mathematical analysis, and numerical modeling. In support of this
study, a bathymetric survey of both inlets was made in October 2002, together with
limited measurements of the water level and current. The acquired process data, together
with previous measurements, modeling, and morphologic analysis, allow examination of
the stability of the subject inlets.
Figure 1-7. Goldsmith Inlet with view northeast into Long Island Sound, showing
substantial gravel and cobble, 22 March 2003
The objective of this study is to improve understanding of the factors that contribute
to the stability of channel cross-sectional area and location and orientation for small inlets
that may in part be controlled by the presence of coarse sediment. The morphology and
morphology change at Mattituck Inlet and Goldsmith Inlet are explored through
comparisons of channel cross sections and beach profiles and by generating topographic
difference maps for Mattituck Inlet. Morphologic analysis identifies areas of erosion and
deposition, while yielding information on sediment bypassing and ebb and flood shoal
formation. Waves and currents combine to form the longshore current, the predominant
mechanism of coastal sediment transport. Numerical modeling of the tidal
10 Chapter 1 Introduction
hydrodynamics for each inlet serves to identify the mechanisms that contribute to the
observed morphologic formations.
Chapter 1 Introduction 11
2 Study Area and Physical
Setting
This chapter describes the study area, the physical setting of Mattituck Inlet and
Goldsmith Inlet, and the regional setting of the north shore of Long Island, the Long
Island Sound. The configuration of Long Island Sound exerts significant control on the
tide, waves, and current that act upon the two inlets. Aspects of the geomorphology of
the north shore of Long Island are also reviewed as they pertain to the sediment source
for these inlets. Discussion of the history and setting of each inlet follows to understand
the regional, economic, and environmental significance of the inlets.
Regional Setting – Long Island Sound
Mattituck Inlet and Goldsmith Inlet connect to the Long Island Sound, a
semienclosed water body open to the Atlantic Ocean at both ends (Figure 2-1). Long
Island Sound is approximately 110 miles long and 20 miles wide at its center. It narrows
to about 10 miles at its eastern extreme, where it meets the Atlantic Ocean through Block
Island Sound, and to less than 1 mile at its western extreme where it meets the East River,
New York Harbor, and ultimately the Atlantic Ocean. Long Island Sound has a surface
area of 1,268 square miles (Koppelman et al. 1976) and is oriented along a southwest-
northeast axis, as is the depression that runs along its center. The depth of Long Island
Sound along this depression is 110-130 ft, and the mean depth of the sound is 60 ft. The
maximum depth of near 300 ft is found in an area known as The Race, a constricted
channel that connects Long Island Sound to Block Island Sound.
Geomorphic environment
Long Island Sound lies on the northern edge of the Atlantic Coastal Plain and is one
of several basins that occupy the New England part of the Atlantic Coastal Plains
province. Long Island Sound can be characterized as five separate basins separated by
shoals of varying relief. Mattituck Inlet and Goldsmith Inlet connect to the sound in an
area bounded by the New Haven shoal and Six Mile Reef (Williams 1981). The southern
boundary of Long Island Sound, the north shore of Long Island is classified as a glacial
deposition coast (Shepard 1963) and is composed primarily of glacial till deposits. These
deposits originated from a group of terminal moraines created by the continental glaciers
that advanced upon the area during the Wisconsin stage of the Pleistocene Epoch, 70,000
to 10,000 years ago.
12 Chapter 2 Study Area and Physical Setting
Long Island Sound
Atlantic Ocean
Block Island
The Race Block Island Sound
Long Island Sound
Atlantic Ocean
Block Island
The Race Block Island Sound
Figure 2-1. Long Island Sound region bathymetry
The south shore and north shore of Long Island differ significantly. The south shore
is an outwash plain characterized by sand-sized sediments and a gentle slope. The gentle
slope found on the south shore is a controlling factor in the observed large bay sizes and
the presence of barrier islands. In contrast, the proximity of the north shore to the Harbor
Hill moraine is a controlling factor in the coarser sediment, steeper slope, and absence of
barrier islands found here. The Harbor Hill moraine begins in the west end of Long
Island and extends in a northeasterly direction to form the northern fork of Long Island
with its terminus at Orient Point. A second terminal moraine, the Ronkonkoma Moraine,
begins in the western portion of Long Island and extends to the southeast (Figure 2-2).
The western extent of the north shore of Long Island is characterized by a series of
narrow bays that extends south to the Harbor Hill Moraine. These bays are believed to
have been formed by protruding lobes of ice attached to the Wisconsin stage glacier that
advanced upon the region. The ice lobes carved the valleys that form the bays and thrust
the material southward, forming the steep bluffs found there. A secondary factor may
have been the action of “spring sapping,” where underground springs loosen the sand
found in these valleys, allowing for rapid erosion (Fuller 1914).
Chapter 2 Study Area and Physical Setting 13
Harbor Hill Moraine
Ronkonkoma Moraine
Harbor Hill Moraine
Ronkonkoma Moraine
Figure 2-2. Harbor Hill and Ronkonkoma Moraine locations (approximate)
The eastern portion, where Mattituck Inlet and Goldsmith Inlet are located, largely
comprises steep bluffs separated by headland areas. The remnant headlands (Herod,
Roanoke, Jacobs, Duck Pond, and Horton Points) are composed of clay and till, and are
more resistant to erosion than adjacent areas (New York District 1969). The bluffs are
characterized by loosely consolidated material, as a mixture of moraine material and
glacial outwash, and they are often directly exposed to waves, thus acting as a sediment
source for longshore transport. McClimans (1970)1 studied bluff erosion along the
Suffolk County portion of the north shore of Long Island and estimated annual recession
rates of 0.5 m/year (1.64 ft/year) at Horton Point, and 0.6 m/year (1.97 ft/year) 0.7 miles
west of Orient Point. Bokuniewicz and Tanski (1983) studied erosion of 50 miles of
coastal bluffs along the eastern end of the north shore of Long Island and concluded that
bluff erosion rates were large enough to satisfy the longshore sediment transport potential
along the eastern portion of the north shore of Long Island. Batten and Kraus (2005)
discuss loss of finer sediments from the beach to the offshore because of the predominant
steep wind waves in the Long Island Sound.
Mattituck Inlet is bounded by two headlands, Jacobs Point to the west and Duck Pond
Point to the east. Goldsmith Inlet is bounded by Duck Pond Point to the west and by
Horton Point to the east (Figure 2-3). Geological evidence suggests that Goldsmith Pond
was once an embayment that was filled by sediment supplied from these headlands. As
sediment deposition narrows the entrance of an embayment, the tidal current increases in
velocity and scouring efficiency. An inlet achieves equilibrium if the deposition caused
by longshore sediment transport is balanced by the erosion caused by tidal current scour
(Johnson 1919). Goldsmith Inlet appears to be an inlet in such a near-equilibrium state.
1 McClimans, R. J. (1970). “Suffolk County bluff and shore recession,” U.S. Department of Agriculture,
Soil Conservation Service, Riverhead, NY, unpublished manuscript.
14 Chapter 2 Study Area and Physical Setting
D
u
c
k
P
o
n
d
P
o
i
n
t
H
o
r
t
o
n
P
o
i
n
t
G
o
l
d
s
m
i
t
h
I
n
l
e
t
M
a
t
t
i
t
u
c
k
I
n
l
e
t
J
a
c
o
b
s
P
o
i
n
t
Long Island Sound
Peconic Bay
Figure 2-3. Study area headlands
Oceanographic environment
Water movement within Long Island Sound is controlled by the tide and is influenced
by wind waves, wave-induced current, wind-induced current, and storms. The geometry
and length of Long Island Sound create a wide variation of tidal range and tidal current
speed.
Tide and storm surge. The tide within Long Island Sound is predominantly
semidiurnal. The length and depth of the water body is such that it is approximately a
quarter-wave resonator for the semidiurnal tide, resulting in mean tide amplitudes that
increase by a factor of three from Block Island Sound to the western end of the sound.
Table 2-1 summarizes mean and spring tide ranges for various locations throughout Long
Island Sound. Tide duration in Long Island Sound is asymmetric, owing to frictional
decay, with ebb tide lasting 15 min longer than flood tide at its eastern end and 30 min
longer at its western end (Signell et al. 2000).
Storm surge is the difference between the observed water level and that predicted at a
given time and location in the absence of a storm, and it is a major agent of coastal
erosion and of inlet and shoreline morphology change. The hurricane of 21 September
1938 produced the water level of record (13.3 ft above mean sea level (msl)) within Long
Island Sound, and the hurricane of 31 August 1954 produced the water level of record
(9.45 ft above msl) for the Suffolk County portion of the north shore of Long Island.
Hurricanes and tropical cyclones are relatively rare in the Long Island region, however,
and are usually oriented to cause water buildup along southern facing coasts, such as the
south shore of Long Island and the southern coast of Connecticut.
Chapter 2 Study Area and Physical Setting 15
Table 2-1
Selected Tide Ranges for Long Island Sound1
Location Mean Tidal Range (ft) Spring Tidal Range (ft)
Plum Island
(Block Island Sound) 2.6 3.1
Mattituck Inlet
(Eastern third) 5.2 6.2
Port Jefferson
(Central third) 6.6 7.6
Hempstead Harbor
(Western third) 7.3 8.6
1 Information obtained from National Oceanic and Atmospheric Administration
(NOAA) National Ocean Service (NOS), Web site: http://tidesandcurrents.noaa.
gov/tides03/tab2ec2a.html.
Extratropical cyclones, colloquially referred to as “northeasters,” are common to this
region and are often oriented to produce water buildup along the north shore of Long
Island (Davies et al. 1971; Davies 1972). New York District (1969) states that
65 moderate to severe northeasters struck the New York coastal area in the 100 years
previous to 1965. Northeasters of lesser intensity occur with much greater frequency and
can also alter inlet morphology. Northeasters are slow moving and can remain in a
region for a number of days, and they can also arrive in succession with short intervals,
days to weeks, in-between.
A severe storm can alter coastal morphology equivalent to months or years of normal
or typical-condition hydrodynamic forcing. The consequences of storm surge and wave
setup on the north shore of Long Island are not explicitly analyzed in this study.
Waves. Wave direction corresponds with wind direction for the limited-fetch water
body of Long Island Sound, and peak wave height corresponds with wind speed. Table
2-2 summarizes the average wind direction taken from wind data at LaGuardia Airport,
located on the western end of the north shore of Long Island. These data can be
considered to be qualitatively representative of wind conditions for the study area.
Table 2-2
Average Wind Direction for Long Island Sound (Town of
Southold 2003)
Direction Percent Occurrence
Northeast 20
Southeast 17
Northwest 30
Southwest 33
Because Long Island Sound is a semienclosed basin, fetch and wind duration are
limited. Wind over Long Island Sound typically originates from the south during the
summer and from the north during the winter. Wind speed and storm duration tend to be
greater during the winter months. Typical summer and winter winds originate from the
16 Chapter 2 Study Area and Physical Setting
western quadrant, producing longshore current and sediment transport directed toward
the east for the central and eastern portions of Long Island. For the study sites, fetch
length for waves originating from the west is considerably larger than the fetch length
from the east. Fetch length for the study area is approximately 50 miles from the
northwest and 20 miles from the northeast (New York District 1969). Larger fetch length
will yield comparatively larger wave heights from the west under similar conditions,
further augmenting the dominant direction of sediment transport.
A wave analysis performed by New York District (1999)1 calculated significant
wave heights and wave periods for various long-term return periods for waves
approaching Mattituck Inlet (Table 2-3). The calculated wave heights listed are for
extreme weather events. Calculated wave directions were from 260 to 280 deg at 10-deg
intervals. Wave height and period for the 10- through 200-year storms have a limited
spread because of the restricted fetch of Long Island Sound.
Table 2-3
Calculated Significant Wave Height and Period (New York
District 19991)
Return Period (year) Significant Wave Height (ft) Period (sec)
10 12.3 6.9
25 13.7 7.3
50 15 7.6
100 16.4 7.9
200 17.4 8.2
Tidal currents. During flood tide, water enters Long Island Sound from the Atlantic
Ocean. Current strength is greatest during this time and greatest at The Race, with a
consistent westward decrease in velocity. Circulation within Long Island Sound is
counterclockwise, with flood current entering to the north and preceding west, and ebb
current running from west to east along the north shore of Long Island (U.S.
Environmental Protection Agency (USEPA) and USACE (2001)). The tidal current has
been observed to decrease consistently with water depth throughout the sound. Current
speed for Long Island Sound is asymmetric. Western and Central Long Island Sound are
flood-dominant, where flood-tide speeds are about 1-3 cm/sec greater than ebb speeds.
In eastern Long Island Sound, ebb tide speeds were found to be about 1-5 cm/sec greater
than flood speeds. Table 2-4 summarizes mean and maximum currents from the study by
the USEPA and USACE (2001). Mean current velocities were calculated by averaging
the mean velocities of a number of current meters that were deployed throughout the
region.
1 U.S. Army Engineer District, New York. (1999). “Mattituck Inlet, New York,” unpublished memorandum.
Chapter 2 Study Area and Physical Setting 17
Table 2-4
Mean and Maximum Measured Tidal Current Velocities for Long
Island Sound (USEPA and USACE 2001)
Location Mean Velocity (cm/sec) Maximum Velocity (cm/sec)
Block Island Sound 37.4 156.9
Eastern third 38.8 136.2
Central third 28.1 91.5
Western third 23.6 110.7
Longshore sediment transport
The ebb tidal current runs from west to east along the Long Island north shore
(USEPA and USACE 2001). Wind-generated surface waves and wave-induced current
combine to produce a longshore current and associated longshore sediment transport. In
Long Island Sound, the predominant wind direction is from the northwest. Wind from
this direction dominates in the winter, when wind speed tends to be greatest and duration
tends to be longest. As a result of their longer fetch from the west as compared to the
east, waves approaching Mattituck Inlet and Goldsmith Inlet from the west will, on
average, tend to be larger and have longer duration than waves originating from the east.
Based on considerations of waves and currents, predominant direction of longshore
sediment transport for this study region is, therefore, from west to east. Storms can also
produce offshore transport of sediment from the headlands and cliffs during times of high
tide combined with storm surge. Bokuniewicz and Tanski (1983) conducted visual
observations of wave height, period, and angle of attack for the eastern portion of the
north shore of Long Island for the period 7-31 May 1981. They concluded that the
transport of sediment was consistently towards the east with the exception of the area
directly on the west side of Mattituck Inlet, where a local reversal in transport, to the
west, was observed.
Only a few estimates of the annual east-directed longshore sediment transport rate are
available for the vicinity of the study sites. Omholt (1974) calculated a longshore
transport potential of 96,000 cu yd/year and noted that the longshore current is not
carrying its full capacity of sediment. Leatherman et al. (1997) arrived at an east-directed
transport rate of 25,000 cu yd/year. This estimate was inferred through the analysis of
volume change of the accretion fillet west of the Goldsmith jetty as seen in historic aerial
photographs. Fields et al. (1999) estimated an east-directed net annual transport rate of
8,000 cu yd/year at Goldsmith Inlet by the same method. They note that this estimate
does not include sediment that may have moved through or around the jetty, and should
be considered a minimum net longshore transport rate to the east. This figure is,
therefore, an estimate of the annual accumulation rate of the fillet west of the Goldsmith
Inlet jetty. Fields et al. (1999) described the maximum potential error for their estimate
as +/- 35 percent (for a maximum fillet accumulation rate of 10,800 cu/yd year).
Bokuniewicz and Tanski (1983) discuss two estimates from other references that
were based on wave hindcasts. Of these, TetraTech (1979) calculated an annual net
longshore transport rate directed to the east of 9 x 107 kg/year. Here, this estimate is
converted to volume by the equation:
18 Chapter 2 Study Area and Physical Setting
(1 )
MV a=−sρ (6-7)
where
V = sediment volume
M = sediment mass
ρs = specific density of the sediment
= sediment porosity a
For this calculation, the porosity was taken to be 0.4 and the specific density 2,650 kg/cu
m, corresponding to quartz sand. The resultant value of 57,000 cu m/year converts to
73,000 cu yd/year and must be considered doubtful because it is inconsistent with
estimates of Leatherman et al. (1997) and Fields et al. (1999), as well as with channel
maintenance volumes, which are much less at Mattituck Inlet. Such a large net rate
implies an even larger gross transport that is not considered feasible for the north shore of
Long Island and the waves in the Long Island Sound.
To estimate the gross longshore sediment transport rate at Goldsmith Inlet, the
present study considers the rate of accumulation at the fillet west of the Goldsmith Inlet
jetty, the annual rate of sediment accumulation in Goldsmith Inlet , the rate of sediment
transported offshore, and the rate of west-directed longshore sediment transport. The
annual rate of accumulation at the fillet is taken to be 8,000 cu yd/year, as inferred from
the analysis by Fields et al. (1999). The annual sediment accumulation rate in Goldsmith
Inlet is at least 5,000 cu yd/ year, based on dredging records (1977 to 1990) and the fact
that sediment is observed to accumulate beyond the point of typical dredging. The rate of
transport offshore is not known, but may be significant given the pronounced depression
located directly offshore of Goldsmith Inlet. The rate of west-directed transport is not
known. Given the previous information and unknowns, the authors conclude that a gross
longshore sediment transport rate of 25,000 cu yd/ year at Goldsmith Inlet is a reasonable
upper limit estimate.
The coast from Duck Pond Point to Horton Point (Figure 2-3) can be considered as a
littoral cell, with the bluffs serving as the sediment source. A littoral cell is a
semienclosed reach of the coast that is relatively isolated sedimentologically from
adjacent coastal reaches and that may contain its own sources and sinks of sediment. The
shoreline from Duck Pond Point to Goldsmith Inlet increases in orientation toward the
east. This change in orientation increases the angle between the crests of the
predominant waves and the shoreline, thereby increasing potential longshore sediment
transport directed to the east. In contrast, the section of shore that includes Mattituck
Inlet is oriented more parallel to the crests of the predominant waves and would,
therefore, be expected to have a smaller east-directed longshore sediment transport rate
for some wave conditions.
As described in Chapter 4, the present study estimates an average-annual sediment
accumulation rate of 8,000 cu yd/year for Mattituck Inlet prior to jetty modifications in
1938 and 1946. Based on this range of rates, a gross sediment transport rate of
25,000 cu yd/year as found for Goldsmith Inlet is judged to be an overestimate for
Mattituck Inlet. Recently, Batten and Kraus (2005) analyzed shoreline change, beach
profile surveys, and dredging records at Mattituck Inlet, and developed a local sediment
budget within the context of a regional budget. The local sediment budget was balanced
Chapter 2 Study Area and Physical Setting 19
with an easterly longshore sediment transport rate of 16,000 cu yd/year and a westerly
rate of 5,000 cu yd/year, yielding a net rate of 11,000 cu yd/year to the east and a gross
rate of 21,000 cu yd/year.
Mattituck Inlet – History and Site Description
Much of the information presented in this section was taken from the Town of
Southold (2003) Local Waterfront Revitalization Plan.
Mattituck Inlet is located in the Village of Mattituck, in the Town of Southold,
Suffolk County, NY. Mattituck Inlet in its natural condition, is depicted in an 1838 NOS
topographic sheet T-55 (Figure 2-4). In its natural condition, Mattituck Inlet is shown to
be directed towards the east. The inlet is of regional economic significance as the only
major harbor east of Port Jefferson Harbor, a distance of 35 miles. The inlet is identified
as one of 10 maritime centers on Long Island Sound by the New York Department of
State (NYDOS). Mattituck Inlet and Creek have historically been of economic
importance as well, as seen from the infrastructure in 1955 (Figure 2-5). The creek was
the site of a tide-gristmill, constructed in 1821, which operated until 1902 (Figure 2-6).
The structure is now the Old Mill Inn Restaurant.
Mattituck Creek serves four marinas and is a commercial and recreational boating
center. The oysters of Mattituck Creek were historically considered to be of the finest
quality and taste (Craven 1906). In 1988, the NYSDEC listed Mattituck Creek as a high-
priority water body problem and the water quality problem as “severe,” an action that
precluded shell fishing in the area. These problems were listed by the NYSDEC as
having “high resolution potential,” and the creek has been the subject of an effort to
improve water quality. At present, the NYSDEC permits conditional shellfish harvesting
in the northern section of Mattituck Creek, whereas the southern portion remains closed.
The water at the mouth of Mattituck Inlet is listed as high quality.
The area around Mattituck Inlet has seen gradual improvement. In 2002, New York
State purchased 9.5 acres of surrounding land to further restore the waterfront and
promote public access.
20 Chapter 2 Study Area and Physical Setting
Figure 2-4. Mattituck Inlet as depicted in NOS T-sheet 55 (1838)
Figure 2-5. Mattituck Inlet and northern end of Mattituck Creek, 11 May 1955
Chapter 2 Study Area and Physical Setting 21
Figure 2-6. Mattituck Mill at Mattituck Creek (by permission Southold Historical Society,
Southold, NY, undated)
Physical description
Mattituck Inlet is a federally maintained inlet with a channel dredged to 7 ft mlw,
with 2-ft overdraft. The New York District dredges Mattituck Inlet every 10-15 years.
Mattituck Creek is 2.5 miles long and two creeks emerge from it. One, Howard’s Creek,
extends to the west and is navigable for its entire length. The other, Long Creek, extends
east and is navigable for about 100 ft beyond its entrance. Mattituck Inlet and Creek
have a surface area of approximately 7,200,000 sq ft, as determined by analysis of an
aerial photograph dated 16 April 2003.
Prior to inlet stabilization, the Mattituck Inlet entrance was narrow, winding, and
shallow (non-navigable). In the Rivers and Harbor Act of 1896, the U.S. Congress
authorized the construction of two jetties to stabilize the inlet and provide reliable
navigation. Work on the jetties commenced in 1901, and construction of the east jetty
was completed in 1906.
Mattituck Inlet has been subject to considerable anthropogenic modification. The first
dredging for channel improvement took place in 1907, and the Federal channel was
completed in 1914 (Ralston 1928). The new work volumes dredged from Mattituck Inlet
and Mattituck Creek are not known. Analysis of New York District condition surveys
indicate that the entire creek had been dredged as of a survey dated August 1913 to April
1914. Mattituck Inlet and Creek were formerly the site of commercial sand and gravel
handling facilities and asphalt tanks. Commercial mining of sand and gravel is known to
have been conducted intermittently within the inlet from 1925 to 1948, under Federal
permit, and mining activities took place on the beach directly west of the west jetty under
Mattituck Park District permit. The beach directly east of Mattituck Inlet has been
nourished by sediment dredged from the inlet. Figure 2-7 displays the approximate
locations of engineering and mining activities in and around Mattituck Inlet.
22 Chapter 2 Study Area and Physical Setting
Figure 2-7. Dredging and mining activities in and near Mattituck Inlet
A chronology of maintenance dredging is given in Table 2-5, and a chronology of
jetty construction, repairs, and modifications is given in Table 2-6. Table 2-7 provides a
summary of the mining permits issued by the New York District. The Mattituck Park
District permitted mining operations on the beach directly west of the west jetty. These
mining operations are documented from 1960 to 1975, and, according to local sources,
continued “on and off” for more than 50 years, as of 1976 (Schubel 1976). Mining
operations came to an end in 1977, a result of a lawsuit brought against the Mattituck
Park District by nearby property owners.1
Schubel (1976) calculated the volumes removed from the beach adjacent to the west
jetty, from 1960 to 1975, based on the rates charged by the Mattituck Park District to the
mining contractors. An overall average rate of $0.50 cu yd was assumed. These
calculations, which partially document the volumes removed through mining, are
presented in Table 2-8. Maintenance dredging at Mattituck Inlet is analyzed in Chapter
4. The implications of the mining practices on sediment transport within and adjacent to
Mattituck Inlet are discussed in Chapters 4 and 7.
1 Personal Communication, 30 August 2004, Mr. Frank Murphy, Mattituck Park District Supervisor (retired).
Chapter 2 Study Area and Physical Setting 23
Table 2-5
Mattituck Inlet Dredging History1
Date Dredged
Dredged Depth
(ft, mlw)
Volume Removed
(cu yd) Disposal Site (If Known)
1907 Unknown Unknown
1914 7 Unknown
June – November 1921 7 13,468
August – September 1923 7 49,500
September – October 1927 7 49,186
November 1935 – May 1936 7 50,785
July – August 1938 7 18,312
September – November 1946 7 53,893 Beach east of east jetty
October – November 1950 7 22,9132 Beach east of east jetty
August – September 1955 7 31,552 Beach east of east jetty
August – October 1961 7 43,550
September – October 1965 7
6,2853
40,9804
May 1980 7 24,137 Beach east of east jetty
October 1990 7 13, 241 Beach east of east jetty
17-24 March 2004 7 13,785 Beach east of east jetty
1 Source: New York District undated compilation; (Ralston 1928).
2 Channel reorientation.
3 Dredged from channel entrance.
4 Dredged from Federal anchorage and southern portion of the channel within Mattituck Creek.
Table 2-6
Mattituck Inlet Jetty Maintenance History1
Date Action Taken Quantity (tons)
1901 Commencement of Federal navigation project
1906 East jetty completed
1910 Sand tightening of landward 680 ft of east jetty, sand
tightening of landward 485 ft of west jetty
1914 First full dredging of the Federal navigation channel
October 1937-August 1938 Repair of outer 100 ft of west jetty
280 ft seaward extension of west jetty
10,000
August – September 1946 Repair of 110 ft of east jetty 100 ft shoreward
extension of east jetty
1,300
May – July 1975 Repairs to east jetty 13,500
1996 Repairs to west jetty
Elevation of seaward 100 ft of west jetty by 1 ft
~16,000
1 Sources: New York District undated compilation; Ralston (1928); Smith (1988)
24 Chapter 2 Study Area and Physical Setting
Table 2-71
Summary of Federal Commercial Sand Mining Permits
Applicant Location
Depth, ft
(mlw)
Date
Granted
Date
Expired
Work
Completed
J.H. Rambo Channel Entrance 10 4/9/1925 12/31/1928 N
Northport Sand and
Gravel S.W. flood shoal 10 9/1/1925 12/31/1928 N
J.H. Rambo Channel Entrance 10 1/29/1929 12/31/1932 Partial
C.H. Benjamin Channel Entrance 12 2/10/1928 12/31/1934*Partial
F.M. Lewis Channel Entrance 12 6/16/1928 12/31/1931 Y
Seely & Walsh
W. Channel
Entrance 20 9/8/1931 12/31/1934 N
Bickel & Wichert Dredging Channel Entrance 20 8/19/1932 12/31/1933 Partial
Bickel & Wichert Dredging Channel Entrance 20 6/30/1934**unknown unknown
Seaboard Sand and
Gravel unknown unknown unknown unknown unknown
J. Cancro Channel Entrance 20 6/30/1933 12/31/1936 Partial
J. Cancro Channel Entrance 20 2/25/1937**12/31/1943 None
1Source: Batten and Kraus (2005)
*extension granted
**extension of previous permit
Table 2-81
Mattituck Park District Permit Sand Mining Volume Estimates
1960-1975
Year Volume Mined (cu yd)
1960 23,214
1961 17,694
1962 14,734
1963 36,098
1964 20,032
1965 26,534
1966 25,808
1967 24,914
1968 15,914
1969 6,482
1970 7,208
1971 8,532
1972 9,502
1973 3,356
1974 364
1975 3.965
1 Source: Schubel (1976)
Chapter 2 Study Area and Physical Setting 25
Specifications of the original navigation project called for construction of two jetties
to the 9-ft mlw contour depth. The distance between the jetties is 400 ft (Figure 2-8 and
Figure 2-9). The jetties, at their original length, did not effectively protect the navigation
channel. The west jetty therefore received a seaward extension in 1938, and it is now
1,320 ft long. An undated compilation of maintenance history at Mattituck Inlet from the
New York District indicates that the east jetty was to receive a shoreward extension of
100 ft in 1946. Analysis of aerial photographs prior to and after this extension indicates
that this extension was approximately 280 ft, an adjustment probably made during
construction to close the breach. The east jetty is now 1,020 ft long. The east jetty was
last repaired in 1975. In 1996, the west jetty was tightened, and the seaward 100-ft
section was elevated 1 ft to reduce sediment intrusion to the inlet (New York District
2003). A condition survey was completed in May 2003, and dredging took place over
17-24 March 2004, removing 13,785 cu yd of sediment. Sediment dredged in 1946, and
thereafter, with the possible exception of the dredging of 1965, was placed on the beach
directly east of Mattituck Inlet. The area of placement for other dredging operations at
Mattituck Inlet is not known.
Figure 2-8. Mattituck Inlet and jetties, view looking south, 28 March 2003
Figure 2-9. Mattituck Inlet and jetties, view looking north, 28 March 2003
26 Chapter 2 Study Area and Physical Setting
The Federal navigation channel is 100 ft wide at the inlet and 80 ft wide in the
interior. Mattituck Creek makes two sharp turns just south of the inlet. The channel
narrows at the turns, where the greatest sediment shoaling takes place (Figure 2-10).
Mattituck Inlet is characterized by sand-sized sediment, shell, and gravel. A recent grain
size sampling of the navigation channel found the main shoaling areas to be composed
mostly of sand and gravel (New York District 2003).
Figure 2-10. Mattituck Inlet channel, after turn eastward inside jetties. Large deposits of
gravel and sand line both sides of channel, 21 November 2003
The Federal navigation channel runs from the inlet entrance to the Village of
Mattituck. The New York District also completed a one-time dredging at the head of
Mattituck Creek in 1965 to create a 460 × 570 ft Federal anchorage. Suffolk County has
twice dredged this area. In 1955, Mattituck Creek was dredged, resulting in the removal
of 1.5 × 106 cu yd of sediment (Allee, King Rosen and Fleming, Inc. et al. 1995). In
1967, Long Creek, a tributary of Mattituck Creek, was dredged, removing 13,000 cu yd.
Physical setting
Steep bluffs bound the beaches surrounding Mattituck Inlet. The bluffs are
composed of loosely consolidated moraine material and glacial outwash. The bluffs
reach maximum elevation (160 ft) to the west (Mattituck Hills), where elevations are
consistently greater than 150 ft. The elevation of the bluffs east of Mattituck Inlet
(Oregon Hills) average 100 ft. Narrow beaches front large sections of the bluffs on either
side. These bluffs serve as a primary sediment source for littoral transport, and portions
of this supply have been removed from the littoral system by recent construction of large
retaining walls (Figure 2-11). The offshore on both sides of Mattituck Inlet contains
Chapter 2 Study Area and Physical Setting 27
large submerged or partially submerged glacial erratics (boulders) that are a hazard to
navigation.
Figure 2-11. Bluffs east of Mattituck Inlet, 21 November 2003
Beach width west of Mattituck Inlet (Breakwater Beach) ranges between 50-100 ft
and can be attributed to impoundment by the west jetty. The beach west of the jetties is
composed mainly of sand. The beach east of the jetty, Bailie’s Beach, is narrower and is
composed of a mixture of sand and gravel. In the past, there was concern that a breach
could occur adjacent to the east jetty. A breach at this location would expose the Oregon
Hills Tidal Wetlands (located just south of the dunes that back Bailie’s Beach) to waves
and would reduce effectiveness of the Federal channel. A study by New York District
(1999)1 concluded that a breach was improbable, because the beach is backed by a row of
primary and secondary dunes (Figures 2-12 to 2-15). Inspection of the area performed on
several occasions during 3 years as part of the present study confirmed the presence of
high dunes and a wide barrier spit (large volume of sediment that will resist storm
erosion). The large sediment volume of the back beach adjacent to the east jetty indicates
a local reversal in longshore transport against the regional west-to-east trend. The dunes
east of Mattituck Inlet appear to be subject to erosion as a result of anthropogenic use
(e.g., Boy Scouts climbing on them.) Figures 2-16 and 2-17 display a vegetated dune
protected by a revetment adjacent to an accessible and unprotected dune with sparse
vegetation.
1 U.S. Army Engineer District, New York. (1999). op cit. p. 16.
28 Chapter 2 Study Area and Physical Setting
Figure 2-12. Bailie’s Beach primary dune, 21 November 2003. Boy Scouts of America
facility is located south of dunes
Figure 2-13. Dunes east of Mattituck Inlet, looking west, 8 October 2002
Chapter 2 Study Area and Physical Setting 29
Figure 2-14. Dunes at base of Mattituck Inlet east jetty, looking south, 21 November
2003
Figure 2-15. Dunes at base of Mattituck Inlet east jetty, looking north, 8 October 2002
30 Chapter 2 Study Area and Physical Setting
Figure 2-16. Vegetated dune protected by revetment at Bailie’s Beach, view looking
east, 9 July 2004
Figure 2-17. Sparsely vegetated and unprotected dune at Bailie’s Beach, view looking
west, 9 July 2004, at same location as photograph shown in Figure 2-16
Chapter 2 Study Area and Physical Setting 31
Mattituck Inlet, Mattituck Creek, and the land surrounding it have been designated as
the Mattituck Inlet Significant Coastal Fish and Wildlife Habitat by the NYDOS. The
perimeter of Mattituck Inlet is fringed with tidal marshes with both intertidal and high
marsh vegetation (Figure 2-18). These wetlands have high primary productivity and
support a variety of wildlife. There are also areas of deposited dredged material along the
shore. The most extensive wetland system is the state-owned Oregon Marsh Tidal
Wetlands, located behind the secondary dunes of Bailie’s Beach. This system supports
juvenile marine finfish, clams, mussels, and osprey.
Figure 2-18. Mattituck Inlet perimeter, view looking south, 21 November 2003
Goldsmith Inlet – History and Site Description
Much of the information presented in this section was taken from the Town of
Southold (2003) Local Waterfront Revitalization Plan and from Comes (1954).
Goldsmith Inlet is located in the Hamlet of Peconic in the Town of Southold, Suffolk
County, NY. Goldsmith Inlet in 1838, as depicted in 1838 NOS topographic sheet T-55,
is shown in Figure 2-19. Similar to Mattituck Inlet in a natural condition (Figure 2-4),
the entrance of Goldsmith Inlet is directed towards the east and has a winding sigmoidal
planform. Although it remains an area of historic, scenic, and environmental
significance, for much of its history it was a site of economic significance also, owing to
a gristmill that was located there. The inlet’s first gristmill was constructed in 1760.
This tidal mill failed to work satisfactorily, was remade into a horse-driven mill, and then
fell into disuse as the local money crop changed from wheat and corn to flax around the
time of the American Revolution.
In 1841, at a cost of $2,100, a group of 80 farmers bought shares to finance the
construction of a new tide-gristmill (Figure 2-20). The Peconic Mill was completed in
1843 and was successful for much of the remainder of the century. The mill stood on the
west bank of Goldsmith Inlet. Owing to the large, semidiurnal tide range (5.2 ft), the
32 Chapter 2 Study Area and Physical Setting
inlet experienced large tidal runs twice a day. Two wooden gates attached to a footbridge
crossing the inlet impounded the high-tide waters that filled Goldsmith Pond.
For much of its existence, the mill was owned by Mr. Gilbert Terry. Mr. Terry added
a windmill wheel to the top tower sometime in the 1870s, allowing the mill to continue to
produce when the creek was frozen (and possibly during times of temporary inlet
closure). The mill ceased operating when the local money crop changed to potatoes and
cauliflower in the 1890s. Newspaper accounts note, “the channel was allowed to fill up
with sand, seaweed, and mussel shoals” (Comes 1954). A large storm on 26-27
November 1889 caused the windmill wheel to fall, and the mill deteriorated. The
structure was torn down in 1906.
Figure 2-19. Goldsmith Inlet as depicted in NOS T-sheet 55 (1838)
Chapter 2 Study Area and Physical Setting 33
Figure 2-20. Peconic Mill at Goldsmith Inlet (by permission Southold Historical Society,
Southold, NY, undated)
Although it is not known when the inlet was first called Goldsmith Inlet, the presence
of a Goldsmith family in the town of Southold can be traced to at least 1668. Southold
was founded in 1640 and is the oldest English town in New York State. The old burying
ground in Cutchogue, also founded in 1640 and believed to be the oldest European burial
ground in New York State, contains many tombstones with the surname Goldsmith on
them from the 1800s (Figure 2-21).
34 Chapter 2 Study Area and Physical Setting
Figure 2-21. Headstone of James H. and Sarah C. Goldsmith, Old Burial Ground,
Cutchogue, NY
Physical description
Goldsmith inlet is now a locally maintained inlet that connects Goldsmith Pond to
Long Island Sound (Figure 2-22). The inlet is non-navigable, and numerous site visits by
the authors indicate it reaches depths of about 0.5-4 ft msl, depending on location and
stage of tide. The inlet width ranges from about 10 to 100 ft, has a mean width of about
50 ft, and is approximately 1,200 ft long. Goldsmith Pond has a mean depth of 2.5 ft msl
(based on survey) and a surface area of approximately 950,000 sq ft as determined from
analysis of an aerial photograph dated 16 April 2003. Goldsmith Inlet is composed of
medium to coarse-grained sand armored with gravel (Figure 2-23).
In 1960, the Suffolk County Department of Public Works proposed the development
of marinas in locations throughout the county, including Goldsmith Inlet (Figure 2-24).
The primary motivation for the construction of the jetty at Goldsmith Inlet is unclear.
Chapter 2 Study Area and Physical Setting 35
The summary report on the workshop examining erosion of the baymouth barrier bar
between Duck Pond Point and Horton Point (Town of Southold 1996)1 concludes “it is
uncertain if the project was meant to address shoreline erosion or prepare the inlet for
construction of a marina and harbor of refuge at Goldsmith Pond.” An introductory
geographic sketch within this same report, however, states “the jetty was intended to
protect the inlet and mitigate erosion immediately to the west.” The transcripts of this
workshop proceedings document discussion on this matter (Town of Southold 1996).
Figure 2-22. Goldsmith Inlet and Goldsmith Pond, 11 May 1955, 9 years before jetty
construction
1 Town of Southold, NY, and New York State Department of State Division of Coastal Resources and
Waterfront Revitalization. (1996). “Report of the workshop examining erosion of the coastal barrier
landform between Duck Pond Point, Town of Southold, NY,” unpulished report.
36 Chapter 2 Study Area and Physical Setting
Figure 2-23. Typical gravel and some cobble armoring at Goldsmith Inlet, 28 March 2003
(view looking west)
Lazy Point Oyster Pond
Napeague Harbor
Acabonack
Harbor
Three Mile Harbor
Northwest
Creek
Majors
Harbor
Paynes
Creek
Mill Creek
North Sea
Harbor
Broadwater
Cove
Smith Cove
Coecles Harbor
O r i e n t H a r b o r
H a s h a m o m u c k P o i n t
G o l d s m i t h I n l e t
0 10 20 Miles NORTH
Proposed Marinas Suffolk County, NY
recreation report prepared by the County of Suffolk, Department of
Planning Hauppauge, NY July 1960
Atlantic Ocean
Long Island
Sound
North Fork
South Fork
Lazy Point Oyster Pond
Napeague Harbor
Acabonack
Harbor
Three Mile Harbor
Northwest
Creek
Majors
Harbor
Paynes
Creek
Mill Creek
North Sea
Harbor
Broadwater
Cove
Smith Cove
Coecles Harbor
O r i e n t H a r b o r
H a s h a m o m u c k P o i n t
G o l d s m i t h I n l e t
0 10 20 Miles NORTH
Proposed Marinas Suffolk County, NY
recreation report prepared by the County of Suffolk, Department of
Planning Hauppauge, NY July 1960
Atlantic Ocean
Long Island
Sound
North Fork
South Fork
Figure 2-24. Proposed marinas, 1960 (redrawn after map of proposed marinas, Suffolk
County, NY, Department of Planning, July 1960)
Chapter 2 Study Area and Physical Setting 37
On 13 August 1962, proceedings by the Suffolk County Board of Supervisors
approved funding for “... the construction of a stone jetty for beach protection on Long
Island Sound at Goldsmith Inlet.” A request by the New York State Department of
Public Works (NYSDPW 1963) to construct a jetty at Goldsmith Inlet was approved by
the New York District on 12 September 1963. An attached drawing plan of the proposed
jetty by the NYSDPW lists the project as “Beach Protection Project 192.” On the same
day, a press release by the NYSDPW announced the receipt of a low-contract bid “for
beach protection work at Goldsmith Inlet.” A memorandum from the NYSDEC, dated
15 May 1979, states “The purpose of the jetty was to maintain the opening at Goldsmith
Inlet and to allow for future development of the Town’s recreational facilities.”
Available literature on the construction of the jetty at Goldsmith Inlet and its subsequent
impact on the adjacent shoreline cite beach protection and the construction of a marina at
Goldsmith Inlet as the motivation for jetty construction (Leatherman 1996;1 Greenman-
Pederson Associates 1981).
Construction of a marina at Goldsmith Inlet was still being considered in 1967. The
transcript of the workshop proceedings indicates that this remained true as of 1973.
Documentation for this date was not, however, provided. A letter dated 30 January 1967
from the Town of Southold Office of the Supervisor to the NYSDPW requests assistance
in procuring state funding to further this aim: “It is the intention of the County Board of
Supervisors to open Goldsmith’s Inlet as a harbor of refuge off Long Island Sound and it
is necessary at this time to construct a jetty on the east side of the inlet, as well as
providing for beach stabilization on the east side.” It is not known whether this request
was made as part of a continuing plan to develop Goldsmith Inlet into a marina, dating
back to the construction of the west jetty, or as a new initiative. The east jetty was never
built, and the project was never completed.
Construction of the jetty was completed in 1964. The cost of construction was
divided equally between New York State and Suffolk County (Town of Southold 1996).
Leatherman (1996) cites a jetty length of 400 ft and Dean (1996),2 in his
recommendations to the Town of Southold, puts the length of the jetty at 460 ft. Original
documents (New York District 1963) and subsequent literature (NYSDEP 1987)3
indicate that the length of the jetty is 310 ft. From analysis of aerial photographs from
1964 to 2003, the present authors conclude that the jetty length is greater than 310 ft,
although a definitive length could not be determined without excavation.
Goldsmith Inlet and Goldsmith Pond have no direct water-dependent uses. The water
quality is considered to be environmentally acceptable at present, but the pond has been
closed for shell fishing since 1996 owing to high bacteria counts. The high coliform
bacteria counts are thought to originate from a stream that discharges into the inlet and
from Autumn Pond, a 1.5-acre pond located to the west that is connected via a drainage
pipe. Non-point sources such as road runoff, septic tanks, and waterfowl waste reduce
1 Leatherman. (1996). op cit p. 9.
2 Dean, R. G. (1996). “Beach erosion control and recommendations,” in Report of the Workshop Examining
Erosion of the Coastal Barrier Landform Between Duck Point and Horton Point, Town of Southold, NY,
Appendix II-B1, unpublished report.
3 New York State Department of Environmental Conservation (NYSDEC). (1987). “Coastal erosion
reconnaissance study,” in Report of the workshop examining erosion of the coastal barrier landform between
Duck Pond Point and Horton Point, Town of Southold, NY, unpublished report.
38 Chapter 2 Study Area and Physical Setting
the pond’s water quality. For these reasons, Goldsmith Inlet has consistently appeared on
the NYSDEC Priority Water Problem List and the Priority Waterbodies List. Closure of
Goldsmith Inlet would be expected to further reduce water quality in the pond.
Physical setting
Goldsmith Inlet is owned by Suffolk County and is located within the county’s 34-
acre Goldsmith Inlet Park. The jetty at Goldsmith Inlet is owned by the Town of
Southold. The park serves the community for nature walks and fishing. The site
supports a variety of wildlife species, including deer, heron, osprey, and piping plovers.
The piping plover is an endangered species whose breeding grounds are protected by the
NYSDEC. A 1998 environmental inventory marked the area as a piping plover nesting
site. This is a factor entering scheduled inlet maintenance, because the NYSDEC will
only allow dredging from October through March. This same inventory also found that
the western side of Goldsmith Inlet contains diverse vegetative habitats including Pitch
Pine and Oak Forest, Maritime Shrubland, Maritime Grassland, Shrub Swamp, Emergent
Marsh, and Estuary and Salt Marsh.
Behind the beach, a narrow fringe of habitat that is classified as an estuary and salt
marsh containing intertidal marsh and high marsh rings the western and southwestern
edge of Goldsmith Inlet and Pond (Figure 2-25). Goldsmith Inlet Park, together with the
Peconic Dunes County Park located directly east of it, contain a system of primary and
secondary dunes not found elsewhere along the North Fork coast. Goldsmith Inlet Park
has been designated as a “critical environmental area” by the Suffolk County Department
of Health and is protected.
Figure 2-25. Goldsmith Inlet, west perimeter, view looking south,
circa winter 2001
The bluff-backed beaches and land surrounding the inlet represent the advanced
stages of a bay barrier, where the pond was once a bay and the barrier beach was formed
from the erosion of coastal glacial deposits. Approaching the inlet from the west, the
bluffs (Figure 2-26) average 40 to 60 ft in elevation and are exposed to waves during
extreme high water. The bluffs decrease in height of 20 to 40 ft with proximity to the
Chapter 2 Study Area and Physical Setting 39
inlet and turn landward, merging with dunes and beaches. Dunes are found east of
Goldsmith Inlet that lead into the Peconic Dunes County Park (Figure 2-27). Kenneys
Road Beach is located further to the east. Sediment removed by periodic dredging of
Goldsmith Inlet is a source of nourishment for this beach, as well as for the beaches
directly east of the inlet.
Figure 2-26. Bluffs west of Goldsmith Inlet, 28 March 2003
Figure 2-27. Goldsmith Inlet entrance with view of east beach, 28 March 2003
Present condition
Suffolk County ceased annual dredging of Goldsmith Inlet in the 1990s. Since then,
the Town of Southold has conducted dredging operations on an as-needed basis.
Emergency dredging took place in winter 2001 and in April 2004. In the past, the
40 Chapter 2 Study Area and Physical Setting
primary motivation for dredging was not necessarily to prevent inlet closure. The town
undertook annual dredging because the sediment found in Goldsmith Inlet, which is
coarser than that found in the beaches, was considered a good source of material for the
eastern beaches. Dredging activities at Goldsmith Inlet are summarized in Table 2-9.
The Town of Southold has dredged Goldsmith Inlet annually since 1991, with the
exceptions of 2002 and 2003.
Table 2-9
Goldsmith Inlet Dredging History (Augmented from Fields
et al. 1999)
Date Dredged Volume (cu yd) Placement Location
1977 4,000 Goldsmith Inlet beach, directly east of inlet
July 1980 3,720 Goldsmith Inlet beach, directly east of inlet
June 1982 6,000 Stockpiled west of inlet, removed off site
July 1985 2,640 Goldsmith Inlet beach, directly east of inlet
June 1987 4,800 Stockpiled and trucked to Kenneys Road Beach
June 1989 4,320 Stockpiled and trucked to Kenneys Road Beach
June 1990 NA Stockpiled and trucked to Kenneys Road Beach
March 2004 Approx. 5,000 Goldsmith Inlet beach, directly east of inlet
Records not available after 1990. It is estimated that approximately 5,000 cu yd of
sediment was dredged annually and trucked to Kenneys Road Beach.
Since 1964, the jetty has gradually deteriorated. Lack of maintenance has caused the
jetty to become porous and lower. Jetty degradation and impoundment of sediment on
the west side of the jetty (Figure 2-28) have apparently led to greater sediment intrusion
into the inlet.1 Records are not available for the volumes dredged in the 1990s. It can be
assumed that the increased sediment intrusion has resulted in continually increasing
dredging volumes since the mid-1990s. The increased sedimentation and lack of recent
dredging have resulted in an inlet that is continually approaching closure.
The unusually cold weather of the winters of 2002 and 2003 may have contributed to
delay closure by the buildup of ice along the shore that reduced wave action and sediment
transport towards the jetty and inlet. Orientation of the inlet entrance to the east may
reduce the effectiveness of the flushing action of the ebb tide by lengthening the channel,
but may be beneficial overall for maintaining inlet stability, discussed in Chapter 6.
1 Personal communication, 24 March 2003, Mr. James McMahon, Community Development Director, Town
of Southold.
Chapter 2 Study Area and Physical Setting 41
Figure 2-28. Sediment impoundment west of Goldsmith Inlet jetty (view looking north),
circa winter 2001
After the bathymetric survey of 6-8 October 2002 (discussed in Chapter 3), the
mouth of Goldsmith Inlet migrated to the east. In the winter months of 2003 and 2004, a
west-oriented spit accreted at the inlet mouth, redirecting the mouth slightly toward the
west. The presence of ice directly east of the inlet may have been partially responsible
for buildup of this west-oriented spit as well as the redirecting of the inlet mouth to the
west.
The Town of Southold requested that Suffolk County dredge the inlet. A permit for
dredging, and the creation of a 4-ft-deep, 40-ft-wide straight channel, was requested in
the winter of 2003/2004 1 . Restrictions brought by piping plover breeding concerns
precluded any action after April 2004. The New York District denied the permit
application because of environmental concerns. A permit was issued to conduct smaller
scale emergency dredging, however, and during 22-26 March 2004, approximately
5,000 cu yd of sediment was removed from the mouth of Goldsmith Inlet to prevent inlet
closure. The material was placed on the adjacent downdrift beach.
Figure 2-29 shows the orientation of the Goldsmith Inlet entrance on 8 October 2002,
Figures 2-30 and 2-31 show the orientation on 28 March 2003 and 16 February 2004,
respectively. The orientation of the Goldsmith Inlet entrance on 6 April 2004, soon after
the emergency dredging of March 2004, is shown in Figure 2-32.
1 Personal communication, 27 January 2004, Mr. James A Richter, Office of the Engineer, Town of Southold.
42 Chapter 2 Study Area and Physical Setting
Figure 2-29. Goldsmith Inlet orientation, 8 October 2002 (view looking northeast)
Figure 2-30. Goldsmith Inlet orientation, 28 March 2003 (view looking east)
Chapter 2 Study Area and Physical Setting 43
Figure 2-31. Goldsmith Inlet orientation and ice, 16 February 2004
(view looking east)
Figure 2-32. Goldsmith Inlet orientation, after emergency dredging, 6 April 2004 (view
looking northeast)
44 Chapter 2 Study Area and Physical Setting
The Town of Southold has discussed the futures of Goldsmith Inlet and the
Goldsmith Inlet jetty. Beyond the creation of a new deeper channel, an option being
considered is shortening of the jetty, which may mitigate erosion east of the jetty yet still
preserve a portion of the beach fillet west of it.
The presence of Autumn Pond must also be considered in assessing the
environmental consequences of actions at Goldsmith Inlet. Autumn Pond connects to
Goldsmith Pond through a drainage pipe. If the inlet were to experience closure, the
relative elevation of the ponds is expected to change, potentially resulting in a reversal of
drainage. Elevated water level in the pond could be a concern for the homeowners in the
vicinity of Autumn Pond,1 as well as alter the environment along the perimeter.
1 Personal communication, 24 March 2003, Mr. James McMahon, Community Development Director, Town
of Southold.
Chapter 2 Study Area and Physical Setting 45
46 Chapter 3 Field Data Collection and Analysis
3 Field Data Collection and
Analysis
As part of this study, a bathymetric survey was performed, and measurements were
made of the water level and current at Mattituck Inlet and Goldsmith Inlet from mid-
September to mid-October 2003. Measurement procedures and results are presented in
this chapter. Previous sediment analysis studies at Mattituck Inlet and Goldsmith Inlet
are also discussed.
Overview of Measurements and Vertical Datums
Shoreline position east and west of these inlets have been surveyed previously (OCTI
1998; Fields et al. 1999), and the New York District surveys the Federal navigation
channel at Mattituck Inlet regularly. Prior to the present study, synoptic bathymetry data
were lacking for the channels and offshore at Mattituck Inlet and Goldsmith Inlet. At
Goldsmith Inlet, prior to the present work, no bathymetric survey of Goldsmith Pond was
available, and at Mattituck Inlet offshore surveys covering the offshore shoal were
available from 1927 and 1967 (the 1927 survey was recovered from archives as part of
this study). Comprehensive surveys allow analysis of morphology change at the inlet
channels and their shoals.
The bathymetric surveys were conducted during 6-8 October 2002. Survey data
presented here are referenced to the horizontal datum New York State Plane Grid, Long
Island Lambert, North American Datum 1983 (NAD83), in feet. Elevations are
referenced to the North American Vertical Datum 1988 (NAVD88) in feet. Horizontal
and vertical controls for the land-based survey were obtained from a March 1998
shoreline survey performed by OCTI (1998). For the period of record of the water-level
gauges deployed in this study, the tidal datum mean sea level was found to be within
survey error of NAVD88 offshore of Mattituck Inlet, at the tip of the west jetty, and
0.25 ft higher than the NAVD88 datum in Mattituck Creek. At Goldsmith Pond, msl
datum for the period of record was found to be 0.91 ft higher than NAVD88. Datum
trees that illustrate the relations between the various datums referenced in this study are
provided in Figures 3-1a and 3-1b.
Water level and current measurements were scheduled for spring tide. The data
collection occurred in autumn, when water level in Long Island Sound tends to be
slightly higher than the annual or long-term average (Lyles et al. 1988). Because of the
wide range in sediment grain size at Goldsmith Inlet (from sand
NA
V
D
8
8
1
(N
O
S
P
o
r
t
J
e
f
f
e
r
s
o
n
6-
8
0
c
t
o
b
e
r
2
0
0
2
O
f
f
s
h
o
r
e
Me
a
n
t
i
d
e
l
e
v
e
l
o
f
R
e
c
o
r
d
6-
8
0
c
t
o
b
e
r
2
0
0
2
M
a
t
t
i
t
u
c
k
C
r
e
e
k
Me
a
n
t
i
d
e
l
e
v
e
l
o
f
R
e
c
o
r
d
6-
8
0
c
t
o
b
e
r
2
0
0
2
G
o
l
d
s
m
i
t
h
P
o
n
d
Me
a
n
t
i
d
e
l
e
v
e
l
o
f
R
e
c
o
r
d
Me
a
n
S
e
a
L
e
v
e
l
(N
O
S
P
o
r
t
J
e
f
f
e
r
s
o
n
)
0.
1
9
f
t
0.
9
1
f
t
2.
9
6
f
t
0.
2
5
f
t
Me
a
n
L
o
w
e
r
L
o
w
W
a
t
e
r
M
a
t
t
i
t
u
c
k
I
n
l
e
t
(N
O
A
A
1
9
6
9
S
e
a
l
e
v
e
l
r
i
s
e
a
d
j
u
s
t
m
e
n
t
)
2
0.
2
6
f
t
1
At
P
o
r
t
J
e
f
f
e
r
s
o
n
,
N
e
w
Y
o
r
k
,
N
O
S
t
i
d
e
g
a
u
g
e
(
S
t
a
t
i
o
n
I
D
8
5
1
4
5
6
0
)
,
l
o
c
a
t
e
d
a
p
p
r
o
x
i
m
a
t
e
l
y
4
8
k
m
w
e
s
t
o
f
M
a
t
t
i
t
u
c
k
I
n
l
e
t
,
1
9
8
3
-
2
0
0
1
t
i
d
a
l
e
p
o
c
h
t
i
d
a
l
d
a
t
u
m
s
m
t
l
a
n
d
m
s
l
ar
e
g
i
v
e
n
a
s
1
.
0
7
6
a
n
d
1
.
0
7
3
m
,
r
e
s
p
e
c
t
i
v
e
l
y
,
a
n
d
N
A
V
D
8
8
d
a
t
u
m
i
s
a
t
1
.
1
3
2
m
w
i
t
h
r
e
s
p
e
c
t
t
o
m
l
l
w
2
At
P
o
r
t
J
e
f
f
e
r
s
o
n
,
N
e
w
Y
o
r
k
,
N
O
S
t
i
d
e
g
a
u
g
e
(
S
t
a
t
i
o
n
I
D
8
5
1
4
5
6
0
)
,
m
e
a
n
s
e
a
l
e
v
e
l
r
i
s
e
i
s
g
i
v
e
n
a
s
2
.
4
4
m
m
/
y
e
a
r
.
Me
a
n
L
o
w
e
r
L
o
w
W
a
t
e
r
(N
O
S
P
o
r
t
J
e
f
f
e
r
s
o
n
)
3.
7
1
f
t
3.
5
2
f
t
Me
a
n
L
o
w
W
a
t
e
r
(N
O
S
P
o
r
t
J
e
f
f
e
r
s
o
n
)
3.
3
f
t
3.
2
2
f
t
Me
a
n
L
o
w
e
r
L
o
w
W
a
t
e
r
M
a
t
t
i
t
u
c
k
I
n
l
e
t
(N
O
S
P
r
e
s
e
n
t
E
p
o
c
h
)
2
NA
V
D
8
8
1
(N
O
S
P
o
r
t
J
e
f
f
e
r
s
o
n
6-
8
0
c
t
o
b
e
r
2
0
0
2
O
f
f
s
h
o
r
e
Me
a
n
t
i
d
e
l
e
v
e
l
o
f
R
e
c
o
r
d
6-
8
0
c
t
o
b
e
r
2
0
0
2
M
a
t
t
i
t
u
c
k
C
r
e
e
k
Me
a
n
t
i
d
e
l
e
v
e
l
o
f
R
e
c
o
r
d
6-
8
0
c
t
o
b
e
r
2
0
0
2
G
o
l
d
s
m
i
t
h
P
o
n
d
Me
a
n
t
i
d
e
l
e
v
e
l
o
f
R
e
c
o
r
d
Me
a
n
S
e
a
L
e
v
e
l
(N
O
S
P
o
r
t
J
e
f
f
e
r
s
o
n
)
0.
1
9
f
t
0.
9
1
f
t
2.
9
6
f
t
0.
2
5
f
t
Me
a
n
L
o
w
e
r
L
o
w
W
a
t
e
r
M
a
t
t
i
t
u
c
k
I
n
l
e
t
(N
O
A
A
1
9
6
9
S
e
a
l
e
v
e
l
r
i
s
e
a
d
j
u
s
t
m
e
n
t
)
2
0.
2
6
f
t
1
At
P
o
r
t
J
e
f
f
e
r
s
o
n
,
N
e
w
Y
o
r
k
,
N
O
S
t
i
d
e
g
a
u
g
e
(
S
t
a
t
i
o
n
I
D
8
5
1
4
5
6
0
)
,
l
o
c
a
t
e
d
a
p
p
r
o
x
i
m
a
t
e
l
y
4
8
k
m
w
e
s
t
o
f
M
a
t
t
i
t
u
c
k
I
n
l
e
t
,
1
9
8
3
-
2
0
0
1
t
i
d
a
l
e
p
o
c
h
t
i
d
a
l
d
a
t
u
m
s
m
t
l
a
n
d
m
s
l
ar
e
g
i
v
e
n
a
s
1
.
0
7
6
a
n
d
1
.
0
7
3
m
,
r
e
s
p
e
c
t
i
v
e
l
y
,
a
n
d
N
A
V
D
8
8
d
a
t
u
m
i
s
a
t
1
.
1
3
2
m
w
i
t
h
r
e
s
p
e
c
t
t
o
m
l
l
w
2
At
P
o
r
t
J
e
f
f
e
r
s
o
n
,
N
e
w
Y
o
r
k
,
N
O
S
t
i
d
e
g
a
u
g
e
(
S
t
a
t
i
o
n
I
D
8
5
1
4
5
6
0
)
,
m
e
a
n
s
e
a
l
e
v
e
l
r
i
s
e
i
s
g
i
v
e
n
a
s
2
.
4
4
m
m
/
y
e
a
r
.
Me
a
n
L
o
w
e
r
L
o
w
W
a
t
e
r
(N
O
S
P
o
r
t
J
e
f
f
e
r
s
o
n
)
3.
7
1
f
t
3.
5
2
f
t
Me
a
n
L
o
w
W
a
t
e
r
(N
O
S
P
o
r
t
J
e
f
f
e
r
s
o
n
)
3.
3
f
t
3.
2
2
f
t
Me
a
n
L
o
w
e
r
L
o
w
W
a
t
e
r
M
a
t
t
i
t
u
c
k
I
n
l
e
t
(N
O
S
P
r
e
s
e
n
t
E
p
o
c
h
)
2
Fi
g
u
r
e
3
-
1
a
.
D
a
t
u
m
e
l
e
v
a
t
i
o
n
d
i
f
f
e
r
e
n
c
e
s
,
P
o
r
t
J
e
f
f
e
r
s
o
n
(
n
o
t
t
o
s
c
a
l
e
)
Chapter 3 Field Data Collection and Analysis 47
NA
V
D
8
8
1
(N
O
S
B
r
i
d
g
e
p
o
r
t
)
NA
V
D
8
8
1
(N
O
S
B
r
i
d
g
e
p
o
r
t
)
Me
a
n
S
e
a
L
e
v
e
l
(N
O
S
B
r
i
d
g
e
p
o
r
t
)
Me
a
n
L
o
w
W
a
t
e
r
(
C
u
r
r
e
n
t
US
A
E
D
C
o
n
d
i
t
i
o
n
S
u
r
v
e
y
s
)
0.
2
2
f
t
2.
7
3
f
t
Me
a
n
L
o
w
W
a
t
e
r
(
8
D
e
c
e
m
b
e
r
1
9
2
7
Se
a
l
e
v
e
l
r
i
s
e
a
d
j
u
s
t
m
e
n
t
)
2
0.
6
f
t
1
At
B
r
i
d
g
e
p
o
r
t
,
C
o
n
n
e
c
t
i
c
u
t
,
N
O
S
t
i
d
e
g
a
u
g
e
(
S
t
a
t
i
o
n
I
D
8
5
1
4
5
6
0
)
,
l
o
c
a
t
e
d
a
p
p
r
o
x
i
m
a
t
e
l
y
4
8
k
m
w
e
s
t
o
f
M
a
t
t
i
t
u
c
k
I
n
l
e
t
,
1
9
8
3
-
2
0
0
1
ti
d
a
l
e
p
o
c
h
t
i
d
a
l
d
a
t
u
m
s
m
t
l
a
n
d
m
s
l
a
r
e
gi
v
e
n
a
s
1
.
1
0
1
a
n
d
1
.
1
0
4
m
,
r
e
s
p
e
c
t
i
v
e
l
y
,
a
n
d
N
A
V
D
8
8
d
a
t
u
m
i
s
a
t
1
.
1
7
1
m
w
i
t
h
r
e
s
p
e
c
t
t
o
m
l
l
w
2
At
B
r
i
d
g
e
p
o
r
t
,
N
e
w
Y
o
r
k
,
N
O
S
t
i
d
e
g
a
u
g
e
(
S
t
a
t
i
o
n
I
D
8
5
1
4
5
6
0
)
,
m
e
a
n
s
e
a
l
e
v
e
l
r
i
s
e
i
s
g
i
v
e
n
a
s
2
.
5
8
m
m
/
y
e
a
r
.
3
Ne
w
Y
o
r
k
D
i
s
t
r
i
c
t
C
o
n
d
i
t
i
o
n
S
u
r
v
e
y
s
Me
a
n
L
o
w
e
r
L
o
w
W
a
t
e
r
(N
O
S
B
r
i
d
g
e
p
o
r
t
)
3.
8
4
f
t
3.
6
2
f
t
Me
a
n
L
o
w
W
a
t
e
r
(N
O
S
B
r
i
d
g
e
p
o
r
t
)
3.
3
8
f
t
US
A
E
D
,
N
e
w
Y
o
r
k
M
e
a
n
S
e
a
Le
v
e
l
,
1
9
0
6
o
b
s
e
r
v
a
t
i
o
n
(R
e
l
a
t
i
o
n
t
o
N
O
S
B
r
i
d
g
e
p
o
r
t
Me
a
n
S
e
a
L
e
v
e
l
i
s
n
o
t
k
n
o
w
n
)
Mean Low Water
(F
t
.
S
c
h
u
l
y
e
r
,
N
Y
)
(0
.
7
6
c
o
n
v
e
r
s
i
o
n
f
a
c
t
o
r
)
0.
3
f
t
3.
5
9
f
t
2.
2
f
t
3
NA
V
D
8
8
1
(N
O
S
B
r
i
d
g
e
p
o
r
t
)
NA
V
D
8
8
1
(N
O
S
B
r
i
d
g
e
p
o
r
t
)
Me
a
n
S
e
a
L
e
v
e
l
(N
O
S
B
r
i
d
g
e
p
o
r
t
)
Me
a
n
L
o
w
W
a
t
e
r
(
C
u
r
r
e
n
t
US
A
E
D
C
o
n
d
i
t
i
o
n
S
u
r
v
e
y
s
)
0.
2
2
f
t
2.
7
3
f
t
Me
a
n
L
o
w
W
a
t
e
r
(
8
D
e
c
e
m
b
e
r
1
9
2
7
Se
a
l
e
v
e
l
r
i
s
e
a
d
j
u
s
t
m
e
n
t
)
2
0.
6
f
t
1
At
B
r
i
d
g
e
p
o
r
t
,
C
o
n
n
e
c
t
i
c
u
t
,
N
O
S
t
i
d
e
g
a
u
g
e
(
S
t
a
t
i
o
n
I
D
8
5
1
4
5
6
0
)
,
l
o
c
a
t
e
d
a
p
p
r
o
x
i
m
a
t
e
l
y
4
8
k
m
w
e
s
t
o
f
M
a
t
t
i
t
u
c
k
I
n
l
e
t
,
1
9
8
3
-
2
0
0
1
ti
d
a
l
e
p
o
c
h
t
i
d
a
l
d
a
t
u
m
s
m
t
l
a
n
d
m
s
l
a
r
e
gi
v
e
n
a
s
1
.
1
0
1
a
n
d
1
.
1
0
4
m
,
r
e
s
p
e
c
t
i
v
e
l
y
,
a
n
d
N
A
V
D
8
8
d
a
t
u
m
i
s
a
t
1
.
1
7
1
m
w
i
t
h
r
e
s
p
e
c
t
t
o
m
l
l
w
2
At
B
r
i
d
g
e
p
o
r
t
,
N
e
w
Y
o
r
k
,
N
O
S
t
i
d
e
g
a
u
g
e
(
S
t
a
t
i
o
n
I
D
8
5
1
4
5
6
0
)
,
m
e
a
n
s
e
a
l
e
v
e
l
r
i
s
e
i
s
g
i
v
e
n
a
s
2
.
5
8
m
m
/
y
e
a
r
.
3
Ne
w
Y
o
r
k
D
i
s
t
r
i
c
t
C
o
n
d
i
t
i
o
n
S
u
r
v
e
y
s
Me
a
n
L
o
w
e
r
L
o
w
W
a
t
e
r
(N
O
S
B
r
i
d
g
e
p
o
r
t
)
3.
8
4
f
t
3.
6
2
f
t
Me
a
n
L
o
w
W
a
t
e
r
(N
O
S
B
r
i
d
g
e
p
o
r
t
)
3.
3
8
f
t
US
A
E
D
,
N
e
w
Y
o
r
k
M
e
a
n
S
e
a
Le
v
e
l
,
1
9
0
6
o
b
s
e
r
v
a
t
i
o
n
(R
e
l
a
t
i
o
n
t
o
N
O
S
B
r
i
d
g
e
p
o
r
t
Me
a
n
S
e
a
L
e
v
e
l
i
s
n
o
t
k
n
o
w
n
)
Mean Low Water
(F
t
.
S
c
h
u
l
y
e
r
,
N
Y
)
(0
.
7
6
c
o
n
v
e
r
s
i
o
n
f
a
c
t
o
r
)
0.
3
f
t
3.
5
9
f
t
2.
2
f
t
3
Fi
g
u
r
e
3
-
1
b
.
D
a
t
u
m
e
l
e
v
a
t
i
o
n
d
i
f
f
e
r
e
n
c
e
s
,
B
r
i
d
g
e
p
o
r
t
(
n
o
t
t
o
s
c
a
l
e
)
48 Chapter 3 Field Data Collection and Analysis
Chapter 3 Field Data Collection and Analysis 49
to cobble), sediment samples were collected there and analyzed to explore possible
relations among grain size, water movement, and inlet channel cross-sectional stability.
Mattituck Inlet
The 6-8 October 2002 survey of Mattituck Inlet, Mattituck Creek, and the offshore
area adjacent to Mattituck Inlet, was made with an Innerspace 448 high-precision echo
sounder and a Global Positioning System (GPS). Horizontal positional accuracy is
approximately +/-1 m. The Innerspace 448 is a survey-grade depth sounder that employs
a transducer with an 8-deg sounding beam and operates at a frequency of 208 kHz. The
beaches adjacent to the inlet and the area from the shoreline seaward to wading depth
were surveyed with land-based equipment (total station and surveying rod).
At Mattituck Inlet, two Seabird26 Paroscientific Digiquartz Pressure Sensor-based
tide gauges were deployed for the period 19 September - 8 October 2002. Two SonTek
side-looking (SL) acoustic Doppler current meters were deployed for the period 7-8
October 2002. Current Meter 1 was placed adjacent to Tide Gauge 2. Grain-size
properties of sediment samples collected 6-7 May 2003 and analyzed by the New York
District are also discussed.
Bathymetry
The extent of the survey for the Mattituck Inlet study area is shown in Figure 3-2,
and interpolated elevation contours for the Mattituck Inlet study area are plotted in Figure
3-3. The survey data were brought into ArcView 3.3 for display and data cleaning.
Areas of shoaling within the inlet, the Federal navigation channel, the channel that runs
through Mattituck Creek, and the Federal anchorage at the end of the creek are observed.
A shoal of unknown origin is located east of the inlet. It is doubtful that this feature is an
ebb shoal. This morphologic feature, longshore bars west of the inlet, the Federal
navigation channel, and the areas of shoaling within the inlet are discussed in the
following sections.
Offshore and east offshore shoal morphology. Figure 3-4 shows the locations of
the offshore survey transects of 6-8 October 2002 west of Mattituck Inlet. Beach profiles
derived from the survey are shown in Figures 3-5a and 3-5b. From the berm crest to a
depth of approximately 10 ft, the beach slope is 1:15. Three longshore sandbars and a
relatively uniform shoreline are observed. The relatively uniform shoreline west of the
inlet is shown in Figure 3-6. Figure 3-7a indicates these longshore bars west of the inlet
and Figure 3-7b indicates the lack of longshore bars east of the inlet. The most landward
or inner longshore bar is located approximately 250 ft offshore, trends toward the
shoreline 2,500 ft west of the inlet, and extends for approximately 7,500 ft west. The
second longshore bar, referred to in this report as the main longshore bar, is located
approximately 750 ft offshore. The main longshore bar begins approximately 2,000 ft
west of Mattituck Inlet, where it trends in towards the shoreline, and continues for at least
28,000 ft. The most seaward bar runs from the tip of the west jetty to 4,300 ft west of the
jetty, where it attaches to the main longshore bar. Adjacent to the east jetty, a bypassing
bar is observed, that connects to the most seaward longshore bar east of the inlet.
Seaward of these bars, the slope is gentler, at approximately 1:125, from 1,400 to 2,500 ft
offshore.
50 Chapter 3 Field Data Collection and Analysis
Figure 3-2. Mattituck Inlet bathymetry survey coverage, 6-8 October 2002
Chapter 3 Field Data Collection and Analysis 51
Figure 3-3. Mattituck Inlet elevation contours, 6-8 October 2002
52 Chapter 3 Field Data Collection and Analysis
Figure 3-4. Mattituck Inlet offshore west survey transects, 6-8 October 2002
W 1
W2
W 3
W 4
W 5
-40
-30
-20
-10
0
10
20
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
6-8 October 2002 Profiles
West of Mattituck Inlet
-100 400 900 1400 1900 2400 2900
Distance Across Shoreline, ft
Figure 3-5a. Beach profiles W1-W5, west of Mattituck Inlet, 6-8 October 2002
Chapter 3 Field Data Collection and Analysis 53
W 6
W 7
W 9
W 10
W 8
-40
-30
-20
-10
0
10
20
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
6-8 October 2002 Profiles
West of Mattituck Inlet
-100 400 900 1400 1900 2400 2900
Distance Across Shoreline, ft
Figure 3-5b. Beach profiles W6-W10, west of Mattituck Inlet, 6-8 October 2002
Figure 3-6. Shoreline west of Mattituck Inlet, 21 November 2003
Fi
g
u
r
e
3
-
7
a
.
L
o
n
g
s
h
o
r
e
b
a
r
s
w
e
s
t
o
f
M
a
t
t
i
t
u
c
k
I
n
l
e
t
,
1
6
A
p
r
i
l
2
0
0
3
Fi
g
u
r
e
3
-
7
b
.
O
f
f
s
h
o
r
e
e
a
s
t
o
f
M
a
t
t
i
t
u
c
k
I
n
l
e
t
,
1
6
A
p
r
i
l
2
0
0
3
54 Chapter 3 Field Data Collection and Analysis
Chapter 3 Field Data Collection and Analysis 55
Locations of the survey transects of 6-8 October 2002 for the offshore area east of
Mattituck Inlet are shown in Figure 3-8, and beach profiles derived from this survey are
shown in Figures 3-9a and 3-9b. In contrast to the almost uniform or smooth shoreline
west of the inlet, the shoreline east of the inlet is characterized by a series of cuspate
formations composed of a sand and gravel mix (Figures 3-7b, 3-10 and 3-11). The
beaches directly east of Mattituck Inlet also contain an abundance of shells from the
bivalve Crepidula fornicata, a native species known as a slipper limpet or common boat
shell (Figure 3-12) that attaches to shells and stones on substrata around the lower range
of the tidal zone.
The slope from the berm crest to approximately 10 ft mlw is 1:25 for the area directly
east of the inlet to approximately 500 ft. The slope becomes gentler after this point, at
1:50.
Figure 3-8. Mattituck Inlet offshore east survey transects, 6-8 October 2002
56 Chapter 3 Field Data Collection and Analysis
E 1
E 2
E 3
E 4
E 5
-100 400 900 1400 1900 2400 2900
Distance Across Shoreline, ft
-40
-30
-20
-10
0
10
20
De
p
t
h
,
f
t
N
A
V
D
8
8
6-8 October 2002 Profiles
East of Mattituck Jetty
Figure 3-9a. Beach profiles E1-E5, east of Mattituck Inlet, 6-8 October 2002
6-8 October 2002 Profiles
East of Mattituck Jetty
E 6
E 7
E 8
E 9
E 10
-100 400 900 1400 1900 2400 2900
Distance Across Shore, ft
-40
-30
-20
-10
0
10
20
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
Figure 3-9b. Beach profiles E6-E10, east of Mattituck Inlet, 6-8 October 2002
Chapter 3 Field Data Collection and Analysis 57
Figure 3-10. Beach east of Mattituck Inlet, 16 April 2003, showing irregular shoreline
Figure 3-11. Cuspate shoreline features east of Mattituck Inlet, 21 November 2003
58 Chapter 3 Field Data Collection and Analysis
Figure 3-12. Mound of slipper limpet shells, east of Mattituck Inlet, 21 November 2003
The area offshore east of the inlet lacks longshore sandbars and possesses a shoal,
displayed in Figure 3-13, oriented parallel to the shoreline. Its center line is located
approximately 1,600 ft offshore, and the shoal is approximately 2,100 ft long and 400 ft
wide at its center. The minimum water depth above the crest is 9.3 ft NAVD88. The
volume of the shoal is approximately 460,000 cu yd, measured from a reference datum of
–21.5 ft NAVD88 (Chapter 4). The feature has an unusual rectangular shape that
contrasts with the more characteristic semi-circular or horseshoe shape of ebb shoals
found at many Atlantic Ocean inlets, including the south shore of Long Island. For this
and other reasons discussed in Chapter 6, the feature is not considered to be an ebb shoal.
Figure 3-14 displays elevation contours for the main longshore bar, the seaward
longshore bar adjacent to the west jetty tip, the bypassing bar adjacent to the east jetty,
and the offshore shoal. Collectively, these features comprise the sediment bypassing
complex for the area offshore of Mattituck Inlet.
Chapter 3 Field Data Collection and Analysis 59
Figure 3-13. Mattituck Inlet offshore shoal and channel contour
elevation, 6-8 October 2002
Figure 3-14. Features offshore of Mattituck Inlet, 6-8 October 2002
60 Chapter 3 Field Data Collection and Analysis
Flood shoal morphology. Mattituck Creek takes a sharp turn to the northeast just
beyond the landward end of the east jetty. A major portion of the flood shoal is located
on the north bank, directly behind this turn. Shoaling also occurs on the south bank and
at the inlet mouth, along the west jetty (Figures 3-15 to 3-17).
Figure 3-15. Mattituck Inlet flood shoal, 6-8 October 2002
Figure 3-16. Mattituck Inlet flood shoal, eastern bank, view looking west, March 2003
Chapter 3 Field Data Collection and Analysis 61
Figure 3-17. Mattituck Inlet flood shoal, eastern bank, view looking east, 21 November
2003
Navigation channel morphology. The Mattituck Inlet Federal navigation channel is
maintained to a depth of 7 ft mlw with 2 ft allowable overdraft. The most recent
dredgings took place in October 1990 and in March 2004. Figure 3-18 illustrates channel
elevations for the 6-8 October 2002 bathymetric survey. The navigation channel has an
approximate average depth of 12 ft NAVD88 (approximately 9 ft mlw), but depth reaches
16 ft at the turn east from the entrance.
Locations of channel transects are shown in Figure 3-19. Figures 3-20a through 3-
20c display cross sections of the channel, the area of the flood shoal, and the progressive
narrowing of the channel. Figure 3-21 shows the approximate location where this
narrowing occurs. The Federal navigation channel is widest between the jetties. Channel
infilling occurs on the west side near the channel entrance (Transect 2) and on the east
side thereafter. At the channel turn, the bank is steep on the southwest side (Transects 5
through 7), indicating scouring by the ebb current and by waves. Beyond the turn, the
channel narrows and is constricted by the growth of the gravelly beach on the southwest
side (Transects 7 and 8) and by the shore-attached flood shoal on the northern bank
(Transects 9 and 10).
62 Chapter 3 Field Data Collection and Analysis
Figure 3-18. Mattituck Inlet Federal navigation channel elevation, 6-8 October 2002
Figure 3-19. Mattituck Inlet channel transects, 6-8 October 2002
Chapter 3 Field Data Collection and Analysis 63
1
2
3
4
-20
-15
-10
-5
0
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
0 100 200 300 400
Distance Across Channel, ft
Mattituck Inlet 6-8 October 2002
Navigation Channel Cross Sections
West East
Figure 3-20a. Mattituck Inlet channel cross sections 1-4, 6-8 October 2002
5
7
6
Mattituck Inlet 6-8 October 2002
Navigation Channel Cross Sections
-20
-15
-10
-5
0
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
0 100 200 300 400
Distance Across Channel, ft
Southwest Northeast
Figure 3-20b. Mattituck Inlet channel cross sections 5-7, 6-8 October 2002
64 Chapter 3 Field Data Collection and Analysis
10
9
8
Mattituck Inlet 6-8 October 2002
Navigation Channel Cross Sections
South
0 100 200 300 400
Distance Across Channel, ft
-20
-15
-10
-5
0
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
North
Figure 3-20c. Mattituck Inlet channel cross sections 8-10, 6-8 October 2002
Figure 3-21. Mattituck Inlet shore-attached flood shoals on northern and southern banks
of channel, view looking east, 21 November 2003
Chapter 3 Field Data Collection and Analysis 65
Water level
Water level was measured at the two locations shown in Figure 3-22. Tide Gauge 1
was secured to the end of the Mattituck Inlet west jetty. Tide Gauge 2 was secured to a
piling near the town bulkhead and the Old Mill Inn Restaurant (GPS location lat.
41°00.552′N, long. 72°32.942′W). The data were referenced to msl datum of record
(time duration of the October data collection) and converted to the NAVD88 datum. No
conversion was done for the areas offshore, because NAVD88 is 0.059 m (0.2 ft) above
msl in this area of the Long Island Sound1, and the sea surface was not sufficiently calm
to make meaningful the geodetic datum conversion to 0.05-ft accuracy.
Figure 3-22. Mattituck Inlet tide gauge and current meter locations,
19 September-8 October 2002
Water-level data collected during the survey are plotted in Figure 3-23a with respect
to Greenwich Mean Time (GMT). At the time of the data collection, GMT led local time
1 At the Port Jefferson, NY, NOS tide gauge (Station ID 8514560), located approximately 48 km west of the
study site, the 1983-2001 tidal epoch tidal datums mean tide level (mtl) and msl are given as 1.076 and 1.073
m, respectively, and NAVD88 datum is at 1.132 m with respect to mllw.
66 Chapter 3 Field Data Collection and Analysis
(Daylight Savings Time) by 4 hr. Figure 3-23b shows water levels for 5-7 October 2002,
during spring tide. The distance between Tide Gauge 1 and Tide Gauge 2 is
approximately 5,200 ft. Measured tidal ranges varied from 3.8 to 7.2 ft (at both
locations). The mean tide range offshore for the deployment was calculated to be 5.21 ft,
and the mean tide range in Mattituck Creek was calculated to be 5.26 ft. A 1-day spring
tidal range of approximately 6 ft was observed at both locations. Offshore at Mattituck
Inlet, the duration of the average ebb tide (defined as peak to trough) of record was 6 hr,
5 min, and the duration of the average flood tide (trough to peak) was 6 hr, 19 min. In
Mattituck Creek, the duration of the average ebb tide of record was 6 hr, 13 min and the
duration of the average flood tide was 6 hr 10 min. Signell et al. (2000) found that the
duration of the ebb tide in the eastern portion of Long Island Sound is 15 min longer than
the duration of the flood tide in that water body. The reversal to slightly longer flood tide
than ebb in the inlet is attributed to generation of overtides and other nonlinearities as the
tidal wave propagates into shallow water.
The measured mean tide range and spring tide range are consistent with those
provided by NOS for this area.1 The 20-day record indicates a slight increase in tide
range in the inlet as compared to the offshore, attributed to tidal wave shoaling in shallow
water and slight resonance in the enclosed channel system.
Mattituck Jetty
Mattituck Creek
Mattituck Jetty and
Mattituck Creek Water Level
-4
-3
-2
-1
0
Wa
t
e
r
L
e
v
e
l
,
f
t
N
A
V
D
8
8
1
2
3
4
5
September 2002 - October 2002 GMT
9/19 9/24 9/29 10/4 10/9
Figure 3-23a. Mattituck Inlet water level, 19 September – 8 October 2002
1 At the Mattituck Inlet, NY, NOS subordinate station, NOS lists 5.4 ft as mean tide range and 6.2 ft as
spring tide range for Mattituck Inlet.
Chapter 3 Field Data Collection and Analysis 67
Mattituck Creek
Mattituck Jetty
10/610/5 10/7 10/8-4
-2
0
2
4
Wa
t
e
r
L
e
v
e
l
,
f
t
N
A
V
D
8
8
6
5- 7 October 2002 GMT
Mattituck Jetty and
Mattituck Creek Water Level
Figure 3-23b. Mattituck Inlet water level, 4-8 October 2002
The phase lag, τ, between the two water-level gauge locations was calculated by
determining the time difference between the respective peaks and troughs of each tidal
cycle. The modal phase lag for the measurement duration was 6 min, with the median
value of 5.1 min. As expected, the peaks and troughs at Tide Gauge 1 typically led those
of Tide Gauge 2. Because there was a time interval indicating a phase reversal, only
those cycles when the offshore led the back bay were selected to calculate the median
phase lag. From approximately 1400 GMT on 6 October 2002 to 1500 GMT on
7 October 2002, a phase reversal was recorded, when the peaks and troughs inside
Mattituck Creek led those offshore by 12 to 18 min. A change in phase was not observed
at Goldsmith Inlet for this time period. The reason for the reversal is not known.
The median phase lag allows an estimation of the equivalent cross-channel depth of
Mattituck Creek between the two tide gauges. The celerity C of a long wave is
*Cg h=, where g = acceleration of gravity (32.2 ft/sec2), and h* = equivalent average
along-channel and cross-channel depth between the two gauges. With the length λ =
5,200 ft between water-level gauges, the equivalent depth is 22
*λ /τhg= = 9 ft, for τ =
5.1 min (median lag). This value is consistent with the average water depth in the
dredged channel at msl.
68 Chapter 3 Field Data Collection and Analysis
Current
Current Meter 1 was secured to a piling at Peterson’s Marina (GPS coordinates lat.
41°00.842′N, long. 72°33.172′W), adjacent to Tide Gauge 2, at approximately 3-ft water
depth. The instrument was deployed on 7 October 2002 at 2236 GMT and retrieved on
8 October 2002 at 2130 GMT. Current Meter 2 was mounted on a floating barge secured
to shore near the town bulkhead (GPS coordinates lat. 41°00.552′N, long. 72°32.942′W)
in approximately 2-ft water depth. Current Meter 2 was deployed on 7 October 2002 at
2306 GMT and retrieved on 8 October 2002 at 2352 GMT.
A maximum velocity of 0.43 m/sec was recorded at Current Meter 1, and
instantaneous velocities exceeding 0.50 m/sec were recorded at Current Meter 2 (Figure
3-24). The second half of the data record from Current Meter 2, which failed after about
11 hr, was considered questionable and is not presented. Flood current is directed
positive and ebb current is directed negative. The maxima on 8 October 2002 correspond
to the near maximum water elevation at spring tide (Figure 3-23b). This instrument was
secured to a floating barge, and the high-frequency fluctuations are attributable to
movement of the barge with surface waves and wind. The velocity phases and
magnitudes at both locations are consistent. Relative velocities at these point
measurements are not readily compared because of the different water depths and
proximities of the gauges to the channel or jetty. The measurements show plateaus in the
maxima and minima, indicative of nonlinearities in water motion due to tidal wave
shoaling and bottom friction.
13:009:004:0023:00 23:0018:00
8 October 2002 GMT7 October 2002
Meter 2
Meter 1
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
Cu
r
r
e
n
t
V
e
l
o
c
i
t
y
,
m
/
s
e
c
Mattituck Inlet
Figure 3-24. Mattituck Inlet along-channel current velocity, 7-8 October 2002
Chapter 3 Field Data Collection and Analysis 69
Sediment
The New York District collected 16 sediment samples at Mattituck Inlet and
Mattituck Creek on 6 and 7 May 2003. The sampling locations are shown in Figure 3-25.
Of the samples, two (MH7 and MH9) were not analyzed and are not shown. The
location of sample MH14 was uncertain and is not shown. Inspection of samples MH11
through MH16 (taken from the southern portion of Mattituck Creek) indicated that they
contained more than 90 percent silt and clay, so they were not further processed. The
upper and lower portions of samples MH5 and MH8 were analyzed separately because
substrate layering was apparent.
Only the results of the upper portion are presented here for the data interpretation to
be consistent with surface samples taken at Goldsmith Inlet. The New York District
(2003) analysis presented the data grouped in United States Department of Agriculture
(USDA) particle size classes. These results are presented here in phi units. Selected φ
unit conversions to millimeters are given in Table 3-1. Figures 3-26a and 3-26b show the
cumulative grain size for all the samples that were analyzed.
Sediment from the Federal navigation channel near the mouth of the inlet consists of
a mixture of coarse, medium, and fine sand (0 to 3 φ). Sediment from the west side of the
Federal navigation near the landward edge of the west jetty (an area of shoaling)
consisted of gravel and coarse sand (> 0 φ). It is inferred that this is an area where the
flood current initially deposits much of the sediment brought into the inlet. The gravel
and coarse sand remains as a lag deposit under the action of waves striking shore after
entering the inlet, and finer (sand-sized) sediments are transported further into the inlet.
Table 3-1
Phi (φ) Units and Millimeter (mm)
Equivalents
Phi (φ) Units Millimeters
-6 64
-5 32
-4 16
-3 8
-2 4
-1 2
0 1
1 0.5
2 0.25
3 0.125
4 0.0625
70 Chapter 3 Field Data Collection and Analysis
Figure 3-25. Mattituck Inlet sediment sample locations, 6-7 May 2003
Chapter 3 Field Data Collection and Analysis 71
MH4
MH2
MH3
MH1
-2 -1 0 1 2 3 4 5
Grain Size, Phi
0
10
20
30
40
50
60
70
80
90
100
Cu
m
u
l
a
t
i
v
e
P
e
r
c
e
n
t
F
i
n
e
r
Cumulative Grain Size
Mattiuck Inlet
Figure 3-26a. Mattituck Inlet cumulative grain size distribution MH1-MH4, 6-7 May 2003,
(data from New York District (2003))
MH5
MH6
MH8
MH10
-2 -1 0 1 2 3 4 5
Grain Size, Phi
0
10
20
30
40
50
60
70
80
90
100
Cu
m
u
l
a
t
i
v
e
P
e
r
c
e
n
t
F
i
n
e
r
Cumulative Grain Size
Mattituck Inlet
Figure 3-26b. Mattituck Inlet cumulative grain size distribution, MH5, MH6, MH8, and
MH10, 6-7 May 2003, (data from New York District (2003))
72 Chapter 3 Field Data Collection and Analysis
Sediment from the main area of shoaling, near the base of the east jetty, was
composed primarily of very coarse to coarse sand (-1 to 1 φ). Sediment mobilized by
waves that reflect from the west bank, where the inlet turns, may be moved by the flood
current and redeposited here, whereas finer sediments can be transported further into the
inlet. Sediment from approximately 1.5 km up the channel consisted primarily of
medium to fine grained sand (1 to 3 φ), and samples taken beyond this location are
primarily composed of silt and clay (< 4 φ). In summary, it appears that the mixture of
sediment brought into the entrance by the tidal current tends to sort, with the coarser
materials remaining at the bend, where the ebb-tidal current weakens, and the finer
material transported further east into the channel.
Offshore sediment samples were collected and analyzed by the New York District
(1969). Figure 3-27 shows the approximate profile locations for the New York District
study against the interpolated bathymetry data of the 6-8 October 2002 survey. The
profile locations were approximated from a hard copy map of the 1969 survey. Table 3-2
lists the median grain sizes found at Profiles 56 and 57 of this study. Profile 56 is located
500 ft west of the inlet, and Profile 57 is 2,000 ft east of the inlet and, therefore, intersects
the offshore shoal. The report gives the median grain size together with location depth,
and no reference datum is provided. It is assumed that the datum depth of sampling was
the New York District mlw.
Figure 3-27. Mattituck Inlet, New York District (1969) sediment sampling profile locations
Chapter 3 Field Data Collection and Analysis 73
Table 3-2
Grain-Size Analysis, Mattituck Inlet Offshore Area, Profiles 56 and 57
(New York District 1969)
Location Depth
(ft)
(mlw
assumed) Grain Size Classification of Material (percent)
Range of
sizes (mm)
Median grain
size (mm)
Fine
Sand
Medium
Sand
Coarse
Sand Gravel
Profile 56, 500 ft west of Mattituck Inlet
Backshore 0.25 - 19.0 1.09 5 72 9 14
High water 0.25 - 25.4 7.45 3 25 11 61
Midtide 0.50 - 25.4 3.15 0 42 14 44
Low water 0.40 - 19.0 5.95 0 10 26 64
6 0.10 – 4.76 0.57 27 71 2 0
12 0.10 - 1.00 0.40 65 35 0 0
18 0.08 – 2.36 0.25 86 14 0 0
24 0.07 - 2.36 0.26 88 12 0 0
30 0.07 - 2.36 0.37 65 34 1 0
Profile 57, 2,000 ft East of Mattituck Inlet
Backshore 0.10 – 25..4 0.56 34 39 6 21
High water 0.15 – 4.76 0.55 15 83 2 0
Midtide 0.29 – 4.76 0.49 24 75 1 0
Low water 0.27 – 38.1 4.75 7 35 8 50
6 0.13 – 2.36 0.38 60 40 0 0
12 0.10 – 38.1 0.55 21 47 1 31
18 0.10 – 2.36 0.23 90 10 0 0
24 0.09 – 4.76 0.21 90 9 1 0
30 0.08 – 4.76 0.38 59 40 1 0
The center line of the offshore shoal at Mattituck Inlet is located 1,600 ft offshore at a
depth of 10 ft NAVD88. The New York District sample at the depth of 12 ft mlw
(approximately 14.5 ft NAVD88) on Profile 57 is, therefore, located on or near the ebb
shoal. This sample location has a median grain size of 0.55 mm and, significantly, is
composed of 47 percent medium-grain sand and 31 percent gravel. The large amount of
coarse material represents a departure from characteristics of other samples in this study,
where fine to medium grain sand predominate. The coarseness of material on the
offshore shoal as compared to adjacent areas indicates the shoal is a lag deposit under the
tidal current and storm waves breaking on it.
74 Chapter 3 Field Data Collection and Analysis
Goldsmith Inlet
The 6-8 October 2002 bathymetric survey of the offshore adjacent to Goldsmith Inlet
was conducted with an Innerspace 448 high-precision echo sounder and a Global
Positioning System (GPS). Positional accuracy is estimated at +/-1 m. Goldsmith Inlet
and Pond, the beaches adjacent to the inlet, and the area from the shoreline to wading
depth were surveyed with land-based equipment (total survey station and surveying rod).
The survey of Goldsmith Inlet and Goldsmith Pond was conducted on 8 October 2002.
A Seabird26 Paroscientific Digiquartz Pressure Sensor-based tide gauge (Tide
Gauge 3) was deployed from 19 September to 8 October 2002. Flood current velocity
was measured in the inlet from 1323 to 1643 GMT, 8 October 2002 by means of a hand-
held current meter mounted on a pole that was sunk into the bed (see Figure 4-49).
Values were read visually and recorded by hand. Fourteen sediment grab samples were
collected from Goldsmith Inlet on 8 October 2002, supplemented by 17 samples collected
on 31 July 2003. In addition, sediment samples collected and analyzed by the New York
District (2003) for the offshore area at Goldsmith Inlet are discussed here.
Bathymetry
The extent of the survey for the Goldsmith Inlet study area is presented in
Figure 3-28a, and interpolated elevation contours for the Goldsmith Inlet study area are
plotted in Figure 3-28b. An interesting finding of the survey is that Goldsmith Inlet lacks
an ebb shoal. An implication from this observation is that bypassing from west to east
occurs around the jetty, along the spit, and then back to the shore on the east side along a
bypassing bar. In contrast, Goldsmith Inlet possess a well-developed flood shoal
consisting of three lobes. The lobes are located on the east bank, center channel, and
west bank, where Goldsmith Inlet enters Goldsmith Pond.
Chapter 3 Field Data Collection and Analysis 75
Figure 3-28a. Goldsmith Inlet bathymetry survey coverage, 6-8 October 2002
Figure 3-28b. Goldsmith Inlet elevation contours, 6-8 October 2002
76 Chapter 3 Field Data Collection and Analysis
Offshore morphology. The location of the offshore transects of the 6-8 October
2002 survey are shown in Figure 3-29. Figures 3-30a and 3-30b display beach profiles
west of the inlet, and Figures 3-31a and 3-31b display beach profiles west of the inlet.
The area offshore on both sides of Goldsmith Inlet has a steep gradient, with a slope of
approximately 1:10 from the beach to a depth of approximately 18 ft NAVD88 (to
approximately 700 ft offshore). A depression that is oriented parallel to the shoreline is
located from 750 to 2,000 ft offshore, where the depth reaches 22 ft NAVD88.
Figure 3-29. Goldsmith Inlet offshore survey transects, 6-8 October 2002
Chapter 3 Field Data Collection and Analysis 77
W 16-8 October 2002 Profiles
West of Goldsmith Inlet
-25
-20
-15
-10
-5
0
5
10
15
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
-100 400 900 1400 1900 2900 3400
Distance Across Shoreline, ft
2400
W 3
W 2
Figure 3-30a. Beach profiles W1-W3, west of Goldsmith Inlet, 6-8 October 2002
W4
W 5
W 7
W 6
-100 400 900 1400 1900 2400 2900 3400
Distance Across Shoreline, ft
-25
-20
-15
-10
-5
0
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
5
10
15 6-8 October 2002 Profiles
West of Goldsmith Inlet
Figure 3-30b. Beach profiles W4-W7, west of Goldsmith Inlet, 6-8 October 2002
78 Chapter 3 Field Data Collection and Analysis
E 3
E 1
E 2
E 4
E 5
-100 400 900 1400 1900 2400 2900 3400
Distrance Across Shoreline, ft
6-8 October 2002 Profiles
East of Goldsmith Inlet
-25
-20
-15
-5
0
5
10
15
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
-10
Figure 3-31a. Beach profiles E1-E5, east of Goldsmith Inlet, 6-8 October 2002
E 6
E 7
E 8
E 10
E 9
-25
-20
-15
-10
-5
0
5
10
15
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
6-8 October 2002 Profiles
East of Goldsmith Inlet
-100 400 900 1400 1900 2400 2900
Distance Across Shoreline, ft
3400
Figure 3-31b. Beach profiles E6-E10, east of Goldsmith Inlet, 6-8 October 2002
Chapter 3 Field Data Collection and Analysis 79
To the west of the inlet, an elevated formation (shoal) is located 1,000 to 2,000 ft
offshore. Because of this distance, the presence of this formation is not considered to be
a consequence of the presence of either the modern or the historic inlet. The shoreline
west of Goldsmith Inlet is characterized by a relatively uniform shoreline (Figure 3-32
and Figure 3-33), and a large number of glacial erratics. The shoreline east of Goldsmith
Inlet is less uniform (Figure 3-34 and Figure 3-35). The offshore is covered with glacial
erratics as well. In contrast to Mattituck Inlet, there are no longshore bars near
Goldsmith Inlet, which may be attributed to the pronounced depression discussed in the
preceding paragraph.
Figure 3-32. Aerial view of shoreline west of Goldsmith Inlet, 16 April 2003
Figure 3-33. Ground view of shoreline west of Goldsmith Inlet, 28 March 2003
80 Chapter 3 Field Data Collection and Analysis
Figure 3-34. Aerial view of shoreline east of Goldsmith Inlet, 16 April 2003
Figure 3-35. Ground view of inlet entrance and shoreline east of Goldsmith Inlet,
28 March 2003
Flood shoal morphology. The flood shoal at Goldsmith Inlet consists of three lobes
that are located on the east bank, on the west bank, and in the channel where the inlet
enters Goldsmith Pond (Figure 3-36). Because of the mild elevation relief at Goldsmith
Pond, the east and west lobes of the flood shoal are exposed during low water (Figures 3-
37 through 3-39). Figures 3-40a through 3-40c depict the contours of Goldsmith Pond at
low tide, mean tide, and high tide for 8 October 2002. The current velocity and water
level for both study areas were measured during 6-8 October 2002, in coordination with
the bathymetric survey. The current and water-level measurements are discussed in the
following sections.
Chapter 3 Field Data Collection and Analysis 81
Figure 3-36. Goldsmith Pond flood shoal formations, 16 April 2003
Figure 3-37. Goldsmith Inlet flood shoal, west lobe, view looking south, 28 March 2003
82 Chapter 3 Field Data Collection and Analysis
Figure 3-38. Goldsmith Inlet flood shoal, east lobe, view looking south, 9 July 2004
Figure 3-39. Goldsmith Inlet flood shoal, east and west lobe, view looking south, 9 July
2004
Chapter 3 Field Data Collection and Analysis 83
Figure 3-40a. Goldsmith Inlet contours at low tide, 8 October 2002
Figure 3-40b. Goldsmith Inlet contours at mean tide, 8 October 2002
84 Chapter 3 Field Data Collection and Analysis
Figure 3-40c. Goldsmith Inlet contours at high tide, 8 October 2002
Channel morphology. The entrance channel at Goldsmith Inlet is narrow and
shallow. Depths range between 1 and 4 ft NAVD88, and a large in-channel bar
formation in the center of the channel becomes exposed during low tide (Figure 3-41).
The channel has been observed to contain running water at all times during numerous
field visits. At the time of the 6-8 October 2002 survey, the channel was 12 ft wide at the
entrance to the Long Island Sound and expanded to 100 ft at the entrance to Goldsmith
Pond.
An attached shoal is located approximately 800 ft into the inlet on the west bank.
Sediment entering the inlet attaches to the inlet bank, occupying a portion of the inlet
channel (Figure 3-42). Sediment entering the inlet during flood tide is inferred to have
formed this feature. This attachment on the west bank may redirect the ebb and flood
tidal current and decrease the flushing capacity of the inlet. Sediment also approaches
the inlet entrance from the spit that forms adjacent to the jetty. The entrance channel
tends to align to the east, a characteristic that has become more pronounced with growth
of the attachment shoal and the buildup of sediment along the jetty.
Transects were extracted from the 8 October 2002 survey. Because Goldsmith Inlet
is shallow, the survey was made based on changes in relief. Two-dimensional (2-D)
transects were created from a three-dimensional (3-D) bathymetry grid to analyze of the
morphology of Goldsmith Inlet. The transect lines are displayed in Figure 3-43, and
channel cross sections are shown in Figures 3-44a through 3-44c. Figure 3-44a displays
the shallow water at the inlet mouth. A longitudinal linear shoal that is dry during low
tide can be seen in Transects 2 and 3. The relatively large attached shoal that has formed
Chapter 3 Field Data Collection and Analysis 85
on the west bank is illustrated in Figure 3-44b (Transects 5 and 6) and the east lobe of the
flood shoal formation is depicted in Figure 3-44c (Transects 11 and 12).
Figure 3-41. Goldsmith Inlet, channel with shoal, 28 March 2003
Figure 3-42. Goldsmith Inlet attached shoal, 28 March 2003
86 Chapter 3 Field Data Collection and Analysis
Figure 3-43. Goldsmith Inlet channel transects, 8 October 2002
Goldsmith Inlet
8 October 2002
Channel Profiles
-4
-3
-2
-1
0
1
2
3
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
0 2 04 06 08 0 1 0 0
Distance Across Channel, ft
1
2
4
3
EastWest
Figure 3-44a. Goldsmith Inlet channel cross sections 1-4, 8 October 2002
Chapter 3 Field Data Collection and Analysis 87
5
6
7
8
Goldsmith Inlet
Channel Profiles
October 2002
-4
-2
0
2
4
6
El
e
v
a
t
i
o
n
,
f
t
M
S
L
0 2 04 06 08 0 1 0 0
Distance Across Shore, ft
East
West
Figure 3-44b. Goldsmith Inlet channel cross sections 5-8, 8 October 2002
9
10
11
12
0 50 100 150 200 250 300 350 400
Distance Across Channel, ft
Goldsmith Inlet
8 October 2002
Channel Profiles
-6
-4
-2
0
2
4
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
West East
Figure 3-44c. Goldsmith Inlet channel cross sections 9-12, 8 October 2002
88 Chapter 3 Field Data Collection and Analysis
Elevation changes along the channel center line at Goldsmith Inlet are summarized in
Figure 3-45. The entrance, located at the shoreline, presents a sill to tidal flow, as does
the interior of the channel toward the pond. The response of the tidal flow to the sill at
Goldsmith Inlet is discussed in the following paragraphs.
Channel Centerline
-6
-5
-4
-3
-2
-1
0
1
2
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
3
0 500 1000 1500
Distance Across Inlet and Pond, ft
2000
Goldsmith Inlet and Pond
October 2002
Jetty Tip
Shoreline
Channel
Flood Shoal
Pond
Channel Centerline
-6
-5
-4
-3
-2
-1
0
1
2
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
3
0 500 1000 1500
Distance Across Inlet and Pond, ft
2000
Goldsmith Inlet and Pond
October 2002
Jetty Tip
Shoreline
Channel
Flood Shoal
Pond
Figure 3-45. Goldsmith Inlet channel center line elevation, 8 October 2002
Water level
The locations of the tide gauge and the current meter are indicated in Figure 3-46.
Tide Gauge 3 was placed near the southern bank of Goldsmith Pond and secured to the
pond bottom by rebar, because there were no structures available to serve as a mounting
platform. Water level at Goldsmith Pond is plotted in Figure 3-47a, together with that in
Long Island Sound measured at the Mattituck Inlet jetty (Tide Gauge 1). In Goldsmith
Pond, the average water level of the record was 0.91 ft above NAVD88. This means that
the pond does not completely empty to mean sea level, because the water flow is retarded
by the sill in the area of the flood shoal, as indicated in Figure 3-47a and, to a lesser
extent, by the sill near the Long Island Sound shoreline.
The measured tidal range within Goldsmith Pond varied from 1.2 to 3.5 ft NAVD88.
The mean tidal range for the deployment was calculated to be 2.15 ft, with a spring tidal
range of approximately 2.9 ft for the period of record. With the measured tidal range
offshore of Mattituck Inlet as an accurate representation of the tidal range offshore of
Goldsmith Inlet, the reduction in tide at Goldsmith Pond is about 3 ft or half the tidal
range in Long Island Sound.
Chapter 3 Field Data Collection and Analysis 89
Figure 3-46. Goldsmith Inlet tide gauge location, 19 September – 8 October 2002
19 September 2002 - 8 October 2002 GMT
Mattituck Jetty
Goldsmith Pond
-4
-2
0
2
4
Wa
t
e
r
L
e
v
e
l
,
f
t
N
A
V
D
8
8
6 Mattituck Offshore and
Goldsmith Pond Water Level
9/19 9/24 9/29 10/4 10/9
Figure 3-47a. Goldsmith Inlet water level, 19 September – 8 October 2002
90 Chapter 3 Field Data Collection and Analysis
Figure 3-47b plots water levels for 5–7 October 2002, a period of spring tide, and
illustrates the phase lag observed at Goldsmith Inlet. Because the tidal wave travels from
east to west in Long Island Sound, the phase of the tide at Goldsmith Inlet, located
5.2 miles east of Mattituck Inlet will slightly lead that outside of Mattituck Inlet.
Therefore, the calculated phase lags for Goldsmith Inlet are slightly less than the values
given.
10/5 10/6 10/7 10/8-4
-2
0
2
4
Wa
t
e
r
L
e
v
e
l
,
f
t
N
A
V
D
8
8
6
5- 7 October 2002 GMT
Mattituck Offshore and
Goldsmith Pond Water Level
Mattituck Jetty
Goldsmith Pond
Figure 3-47b. Goldsmith Inlet water level, 5–7 October 2002
The times series of water level in Goldsmith Pond, as shown in Figure 3-47a and
more clearly in Figure 3-47b, exhibits three remarkable properties:
a. Low tide usually does not reach 0 NAVD88, which is approximately msl at the
site.
b. The tide range in the pond is less than half that in the Long Island Sound.
c. Water level rises much more rapidly than it falls, and the duration of ebb is much
longer than flood.
Properties (a) and (b) are related. In Goldsmith Pond, the duration of the average ebb
tide (peak to trough) of record was 8 hr, 56 min, and the duration of the average flood
tide (trough to peak) was 3 hr, 28 min.
The bottom of the mouth of Goldsmith Inlet is located approximately at the elevation
of the NAVD88 datum, near the visually observed mean shoreline position. The relation
between NAVD88 and msl at the mouth of Goldsmith Inlet is not known with
confidence. In any case, flow into the inlet and pond can only occur if the water level in
Long Island Sound is above the NAVD88 or msl datums, according to modeling results
described in Chapter 5. When high tide is reached in the sound, high tide in the pond
occurs about 29 min later (median lag) and is 0.25 ft lower. In contrast, the median phase
Chapter 3 Field Data Collection and Analysis 91
lag for the low waters is 195 min. (3.24 hr). Therefore, flow into the inlet and pond can
only occur when the water level in the sound is above msl.
The long-term average water level in Goldsmith Pond is expected to be constant.
The time duration of the high water is much shorter than the duration of the low water
about the mean water level. Because the same amount of water must enter on flood as
leaves at ebb to maintain the average water level in the pond, but in a shorter time, the
average of the inlet channel cross-sectional current velocity on flood must be much
greater than on ebb. Such an inlet is called “flood dominant,” referring to the greater
magnitude, but shorter duration of the flood tide.
Tidal asymmetry of coastal inlets has been well studied (e.g., Boon 1975; Boon and
Byrne 1981; Aubrey and Speer 1985; Speer and Aubrey 1985; Speer et al. 1991, as
summarized by Walton (2002). For example, shoaling in channels truncates the lowest
portion of the tide, resulting in a longer falling tide and a weaker ebb current as compared
to the flood current. Such a truncation is a hypsometric effect, the control of water-
surface elevation by the bathymetry or depth. In the case of Goldsmith Inlet, the
elevation of the entire inlet entrance is located near msl datum in the Long Island Sound.
At the lower water levels of ebb tide, the sills at the flood shoal and shoreline become
effective in retarding flow. In addition, water entering the fringing marsh of Goldsmith
Pond on flood tide has greater velocity than when it exits on ebb. The effective friction
of the marsh, creating storage capacity, releases water slowly on ebb as compared to its
entrance at flood tide.
Current
The hand-held current meter (Current Meter 3) was located approximately at
middepth position (Figure 4-49). Along-channel current velocity at this location is
plotted in Figure 3-48. The flood current velocity reached 1.30 m/sec, when the current
meter had to be removed because of concerns over the rising water level and strong
current on the pole holding the meter. Corresponding to discussion of water level, there
must be a strong asymmetry in current velocity at Goldsmith Inlet, with flood current
being significantly stronger than ebb current. Sediment transport is proportional to a
power of water velocity, typically the third power. Therefore, a flood-dominant inlet will
tend to have net sediment transport directed into the bay, or into Goldsmith Pond in the
present situation.
92 Chapter 3 Field Data Collection and Analysis
14:23 15:4315:03 16:0315:23 16:23
-0.4
0.4
0.8
1.2
1.6
14:43
Meter 3 Goldsmith Inlet
Cu
r
r
e
n
t
V
e
l
o
c
i
t
y
,
m
/
s
e
c
0
Time 8 October, 2002 GMT
Figure 3-48. Goldsmith Inlet midchannel current velocity, 8 October 2002
Sediment
Sample collection sites for 8 October 2002 are shown in Figure 3-49a, and Figure 3-
49b shows the sites of the 31 July 2003 sampling. The photograph serving as
background in these two figures was taken 16 April 2003. For the 8 October 2002
sampling, the inlet mouth was located somewhat to the west as compared to April 2003.
The samples were sieved to determine the grain-size distribution and median grain size of
the surficial sediments at each location. Figures 3-50a through 3-50g show the grain size
cumulative frequency for each sample site.
The surficial sediment at the inlet entrance (Samples 1-10; 15-17) is predominantly
composed of gravel (-6 to -2 φ). A transitional area is located around the shoal attached
to the west bank of the channel (Samples 11-13; 18, and 19), where smaller gravel (-4 to
-2 φ) dominates sand and larger gravel. The area of the inlet south of the transition
region, which includes the flood shoal, and the bottom of Goldsmith Pond, where
samples were taken, is composed primarily of fine gravel and very coarse to coarse sand
(-1 to 1 φ).
Chapter 3 Field Data Collection and Analysis 93
Figure 3-49a. Goldsmith Inlet sediment sample locations, 8 October 2002
Figure 3-49b. Goldsmith Inlet sediment sample locations, 31 July 2003
94 Chapter 3 Field Data Collection and Analysis
S3
S15
S4S2
-6 -4 -2 0 2 4 6
Grain Size (Phi)
Cumulative Grain Size
Goldsmith Inlet
0
10
20
30
40
50
60
70
80
90
100
Cu
m
u
l
a
t
i
v
e
P
e
r
c
e
n
t
F
i
n
e
r
S1
Figure 3-50a. Goldsmith Inlet cumulative grain size S1-S4 and S15, 8 October 2002 and
31 July 2003
S7
S5
S16
-6 -4 -2 0 2 4 6
Grain Size (Phi)
0
10
20
30
40
50
60
70
80
90
100
Cu
m
u
l
a
t
i
v
e
P
e
r
c
e
n
t
F
i
n
e
r
Cumulative Grain Size
Goldsmith Inlet
S8
S6
Figure 3-50b. Goldsmith Inlet cumulative grain size S5-S8 and S16, 8 October 2002 and
31 July 2003
Chapter 3 Field Data Collection and Analysis 95
S9
-6 -4 -2 0 2 4 6
Grain Size (Phi)
Cumulative Grain Size
Goldsmith Inlet
0
10
20
30
40
50
60
70
80
90
100
Cu
m
u
l
a
t
i
v
e
P
e
r
c
e
n
t
F
i
n
e
r
S17
S10
S12
S11
Figure 3-50c. Goldsmith Inlet cumulative grain size S9-S12 and S17, 8 October 2002 and
31 July 2003
S13
S19
S14
-6 -4 -2 0 2 4 6
Grain Size (Phi)
0
10
20
30
40
50
60
70
80
90
100
Cu
m
u
l
a
t
i
v
e
P
e
r
c
e
n
t
F
i
n
e
r
Cumulative Grain Size
Goldsmith Inlet
S18
Figure 3-50d. Goldsmith Inlet cumulative grain size S13, S14, S18, and S19, 8 October
2002 and 31 July 2003
96 Chapter 3 Field Data Collection and Analysis
S21
S20
S22
-6 -4 -2 0 2 4 6
Grain Size (Phi)
0
10
20
30
40
50
60
70
80
90
100
Cu
m
u
l
a
t
i
v
e
P
e
r
c
e
n
t
F
i
n
e
r
Cumulative Grain Size
Goldsmith Inlet
S23
Figure 3-50e. Goldsmith Inlet cumulative grain size S20-S23, 8 October 2002 and 31 July
2003
S25
S27
-6 -4 -2 0 2 4 6
Grain Size (Phi)
0
10
20
30
40
50
60
70
80
90
100
Cu
m
u
l
a
t
i
v
e
P
e
r
c
e
n
t
F
i
n
e
r
Cumulative Grain Size
Goldsmith Inlet
S26
S24
Figure 3-50f. Goldsmith Inlet cumulative grain size S24-S27, 8 October 2002 and 31 July
2003
Chapter 3 Field Data Collection and Analysis 97
S31
S28
-6 -4 -2 0 2 4 6
Grain Size (Phi)
0
10
20
30
40
50
60
70
80
90
100
Cu
m
u
l
a
t
i
v
e
P
e
r
c
e
n
t
F
i
n
e
r
Cumulative Grain Size
Goldsmith Inlet
S29
S30
Figure 3-50g. Goldsmith Inlet cumulative grain size S28-S31, 8 October 2002 and 31 July
2003
Figure 3-51 displays a plan view distribution of sediment grain size at Goldsmith
Inlet. Because exact sampling locations were not recorded, as by GPS, the grain-size
map is approximate. The plan view clearly shows the fining of sediment with distance
into the inlet and pond from the entrance. Current velocity magnitude plays a major role
in determining the distribution of grain size within an inlet, resulting in a graded deposit
and sorting within the channel. The greater velocity magnitude at the inlet mouth will
entrain and transport increasingly larger grain sizes. As the current velocity magnitude
decreases, the larger grain size fractions will be deposited, whereas finer sediments will
be transported further into the inlet.
98 Chapter 3 Field Data Collection and Analysis
Figure 3-51. Goldsmith Inlet median grain-size distribution of surface samples,
8 October 2002 and 31 July 2003
Table 3-3 lists the median grain sizes found at Profiles 59 and 60 from the New York
District (1969) study. Profile 59 is located approximately 200 ft west of Goldsmith Inlet
and Profile 60 is approximately 500 ft east of Goldsmith Inlet. The profile locations are
shown in Figure 3-52. The 1969 study indicates that sediment grain size west of
Mattituck and Goldsmith Inlet is consistently larger than the grain sizes found east of the
inlet.
Chapter 3 Field Data Collection and Analysis 99
Table 3-3
Grain-Size Analysis, Goldsmith Inlet Offshore Area, Profiles 59 and 60
(New York District 1969)
Grain Size Classification of Material (percent)
Location
Depth (ft)
Range of
sizes
(mm)
Median
grain size
(mm)
Fine
Sand
Medium
Sand
Coarse
Sand Gravel
Profile 59, 200 ft west of Goldsmith Inlet
Backshore 0.10 - 25.4 1.50 4 57 14 25
High water
0.15 –
38.1 1.28 7 52 7 34
Midtide
0.15 –
38.1 3.00 7 41 6 46
Low water
0.10 –
38.1 6.00 3 24 14 59
6
0.07 –
25.4 9.50 0 6 10 84
12
0.07 –
2.36 0.45 42 53 2 0
18
0.08 –
25.4 0.23 70 21 2 7
24
0.04 –
9.52 0.23 66 24 6 2
30 0.07 - 2.36 0.22 95 4 1 0
Profile 60, 500 ft east of Goldsmith Inlet
Backshore
0.15 –
2.36 0.52 20 80 0 0
High water
0.15 –
25.4 0.43 49 16 0 35
Midtide
0.17 –
2.36 0.49 25 75 0 0
Low water
0.05 –
19.0 0.69 27 45 5 22
6
0.15 –
2.36 0.40 62 38 0 0
12
0.07 –
4.76 0.43 50 48 2 0
18
0.16 –
4.76 0.48 40 58 2 0
24
0.10 –
4.76 0.43 45 54 1 0
30
0.09 –
2.36 0.44 47 53 0 0
100 Chapter 3 Field Data Collection and Analysis
Figure 3-52. Goldsmith Inlet, New York District (1969) profile locations
Chapter 4 Morphology Change, and Channel Shoaling and Migration 101
4 Morphology Change, and
Channel Shoaling and
Migration
This chapter describes and quantifies morphology change at Mattituck Inlet
from 1891 to present and at Goldsmith Inlet from 1964 to present. For Mattituck
Inlet, change in the offshore and flood shoals, and in the inlet response to the
original navigation project and to subsequent modifications, is analyzed. For
Goldsmith Inlet, change in the channel, inlet orientation, and flood shoal is
analyzed.
Mattituck Inlet
To analyze morphology change for the offshore area at Mattituck Inlet, beach
profiles from the 6-8 October 2002 survey are compared to those from a March
1998 survey (OCTI 1998), spanning a 4-1/2 year interval. The long-term
morphology change of the offshore shoal associated with Mattituck Inlet is
analyzed by comparing a 1927 survey to the survey of 6-8 October 2002. For the
Mattituck Inlet navigation channel and flood shoal, morphology change and
response to jetty modifications is analyzed based upon historic aerial
photographs and data provided by the New York District.
Historic sounding data received from the New York District had been
archived on aperture cards, a form of media that requires a high-resolution
reader. The Hudson Blueprint Company was engaged to read the aperture cards.
Paper maps were produced and scanned in a large-format scanner, and the
resulting images were then calibrated, digitized, and converted into ArcView®
shape files by means of Didger® software.
Offshore morphology change
Beach profiles. Figures 4-1a to 4-1h plot the 1998 (OCTI 1998) and 2002
beach profile survey data for the offshore area west of Mattituck Inlet. Profile
transects were referenced to established monuments (OCTI 1998). Two
longshore bars can be identified on most of the profile lines, and cross-shore,
primarily seaward movement of the bars occurred between 1998 and 2002
(Figures 4-1e to 4-1h). More data sets are required over several years and with
greater frequency to determine the cause of movement as due to seasonal changes
102 Chapter 4 Morphology Change, and Channel Shoaling and Migration
in waves, as a response to seasonal water level, or another cause. The profile
surveys indicate a shoreline near equilibrium with small amounts of advance at
some locations to the west of Mattituck Inlet.
1998
2002
-100 400 900 1400 1900 2400 2900
Distance Across Shore, ft
-40
-30
-20
-10
0
10
20
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
Mattituck Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line W 1 (Approx. 100 ft
West of West Jetty)
Figure 4-1a. Beach profile W1, west of Mattituck Inlet, March 1998 and
6-8 October 2002
1998
2002
-100 400 900 1400 1900 2400 2900
Distance Across Shore, ft
-40
-30
-20
-10
0
10
20
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
Mattituck Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line W 2 (Approx. 600 ft
West of West Jetty)
Figure 4-1b. Beach profile W2, west of Mattituck Inlet, March 1998 and
6-8 October 2002
Chapter 4 Morphology Change, and Channel Shoaling and Migration 103
1998
2002
-100 400 900 1400 1900 2400 2900
Distance Across Shore, ft
-40
-30
-20
-10
0
10
20
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
Mattituck Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line W 3 (Approx. 1,100 ft
West of West Jetty)
Figure 4-1c. Beach profile W3, west of Mattituck Inlet, March 1998 and
6-8 October 2002
1998
2002
-100 400 900 1400 1900 2400 2900
Distance Across Shore, ft
-40
-30
-20
-10
0
10
20
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
Mattituck Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line W 4 (Approx. 1,600 ft
West of West Jetty)
Figure 4-1d. Beach profile W4, west of Mattituck Inlet, March 1998 and
6-8 October 2002
104 Chapter 4 Morphology Change, and Channel Shoaling and Migration
1998
2002
-100 400 900 1400 1900 2400 2900
Distance Across Shore, ft
-40
-30
-20
-10
0
10
20
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
Mattituck Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line W 5 (Approx. 2,100 ft
West of West Jetty)
Figure 4-1e. Beach profile W5, west of Mattituck Inlet, March 1998 and
6-8 October 2002
1998
2002
-100 400 900 1400 1900 2400 2900
Distance Across Shore, ft
-40
-30
-20
-10
0
10
20
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
Mattituck Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line W 6 (Approx. 2,600 ft
West of West Jetty)
Figure 4-1f. Beach profile W6, west of Mattituck Inlet, March 1998 and
6-8 October 2002
Chapter 4 Morphology Change, and Channel Shoaling and Migration 105
1998
2002
-100 400 900 1400 1900 2400 2900
Distance Across Shore, ft
-40
-30
-20
-10
0
10
20
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
Mattituck Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line W 7 (Approx. 3,100 ft
West of West Jetty)
Figure 4-1g. Beach profile W7, west of Mattituck Inlet, March 1998 and
6-8 October 2002
1998
2002
-100 400 900 1400 1900 2400 2900
Distance Across Shore, ft
-40
-30
-20
-10
0
10
20
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
Mattituck Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line W 8 (Approx. 3,600 ft
West of West Jetty)
Figure 4-1h. Beach profile W8, west of Mattituck Inlet, March 1998 and
6-8 October 2002
106 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figures 4-2a to 4-2f plot 1998 (OCTI 1998) and 2002 beach profile survey
for the offshore area east of Mattituck Inlet and cover the shoal located
approximately 1,660 ft offshore. The profiles indicate stability of this feature for
the 4-1/2-year interval and a stable shoreline with small amounts of recession at
some locations to the east of Mattituck Inlet.
1998
2002
-100 400 900 1400 1900 2400 2900
Distance Across Shore, ft
-40
-30
-20
-10
0
10
20
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
Mattituck Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line E 4 (Approx. 600 ft
East of East Jetty)
Figure 4-2a. Offshore shoal cross-shore profile E4, March 1998 and 6-8 October
2002
1998
2002
-100 400 900 1400 1900 2400 2900
Distance Across Shore, ft
-40
-30
-20
-10
0
10
20
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
Mattituck Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line E 5 (Approx. 1,100 ft
East of East Jetty)
Figure 4-2b. Offshore shoal cross-shore profile E5, March 1998 and 6-8 October
2002
Chapter 4 Morphology Change, and Channel Shoaling and Migration 107
1998
2002
-100 400 900 1400 1900 2400 2900
Distance Across Shore, ft
-40
-30
-20
-10
0
10
20
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
Mattituck Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line E 6 (Approx. 1,600 ft
East of East Jetty)
Figure 4-2c. Offshore shoal cross-shore profile E6, March 1998 and 6-8 October
200
1998
2002
-100 400 900 1400 1900 2400 2900
Distance Across Shore, ft
-40
-30
-20
-10
0
10
20
El
e
l
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
Mattituck Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line E 7 (Approx. 2,100 ft
East of East Jetty)
Figure 4-2d. Offshore shoal cross-shore profile E7, March 1998 and 6-8 October
2002
108 Chapter 4 Morphology Change, and Channel Shoaling and Migration
1998
2002
-100 400 900 1400 1900 2400 2900
Distance Across Shore, ft
-40
-30
-20
-10
0
10
20
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
Mattituck Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line E 8 (Approx. 2,600 ft
East of East Jetty)
Figure 4-2e. Offshore shoal cross-shore profile E8, March 1998 and 6-8 October
2002
1998
2002
-100 400 900 1400 1900 2400 2900
Distance Across Shore, ft
-40
-30
-20
-10
0
10
20
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
Mattituck Profile Comparison
Mar. 1998 and Oct 2002
Line E 9 (Approx. 3,100 ft
East of East Jetty)
Figure 4-2f. Offshore shoal cross-shore profile E9, March 1998 and 6-8 October
2002
Chapter 4 Morphology Change, and Channel Shoaling and Migration 109
Change of offshore shoal morphology. To assess long-term change
offshore of Mattituck Inlet, a comparative analysis of the 6-8 October 2002
survey, a 1969 survey by the National Oceanic and Atmospheric Administration
(NOAA) (survey #H09087), and an 8 December 1927 New York District survey
was conducted. Because the 8 December 1927 covered the smallest area, the
spatial extent of this survey defined the area of examination of elevation change
for the periods considered. Elevation change was obtained through surface
differencing, calculated between triangulated irregular network (TIN) grids
generated in ArcView 3.3.
The 8 December 1927 condition survey was conducted approximately
2 months after the dredging of September – October 1927. The New York
District condition survey of 8 December 1927 was referenced to a mlw datum
that lies 2.2 ft below a New York District msl datum as determined in April-May
1906. To adjust the 8 December 1927 survey to the NAVD88 datum, 3.63 ft was
subtracted from the elevation values of this condition survey. The difference
between the datums was derived after Batten and Kraus (2005), and can be
accounted for in the following manner. The mlw datum of reference for the 1927
survey was determined at the NOS tide station at Ft. Schuyler, NY. At Mattituck
Inlet, mlw is 0.3 ft below mlw at Ft Schuyler, NY. According to the NOS, the
conversion factor between Mattituck Inlet and the NOS Bridgeport, CT,
reference station is 0.76, and the difference between mlw and NAVD88 at
Bridgeport, CT, is 3.59 ft. The difference between the present day mlw and
NAVD88 at Mattituck Inlet is therefore 2.73 ft. Sea level has risen
approximately 0.6 ft at Port Jefferson for the 75-year period considered. The
difference between mlw at Mattituck Inlet and Ft. Schuyler (0.3 ft), sea level rise
(0.6 ft), and the calculated elevation of mlw datum in the present tidal epoch
(2.73 ft), yield the adjustment of 3.63 ft applied here. The datum relations are
illustrated in Figure 3-1a and 3-1b.
The 1969 NOAA survey was referenced to mean lower low water (mllw).
The NOS published conversion factor for the 1983-2001 epoch at Mattituck Inlet
defines NAVD88 at 2.96 ft above mllw. According to the NOS tide station at
Port Jefferson, sea level has risen approximately 0.26 ft between 1969 and 2002.
To adjust the mllw datum of this survey to NAVD88, 3.22 ft was subtracted
from the elevation values of this survey. The datum relations discussed here are
illustrated in Figure 3-1a.
The condition survey of 8 October 1927 is referenced to a local coordinate
system. The background aerial photograph shown in Figures 4-3 through 4-5c is
circa 1930. Horizontal conversion to the New York State Plane Grid, Long
Island Lambert, NAD83, was accomplished by georeferencing the data to this
aerial photograph of Mattituck Inlet, and the subsequent digitization of the
adjusted survey points. The root mean square (rms) error in the georeferencing
was 60 ft. The circa 1930 aerial photograph is large scale (1:24,000), and covers
more than 10 miles of shoreline. The rms error is considered reasonable because
Mattituck Inlet is near the center of the aerial photograph, where the estimated
error is less. Overall, mapped high-water line (hwl) lines and jetty and channel
location matched well, and visual inspection of the alignment of the jetties
between the aerial photograph and the 8 December 1927 bathymetry survey
indicated error between 10 to 30 ft.
110 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figures 4-3 and 4-4 displays the elevation contours from the 8 December
1927 survey and the 1969 NOAA survey. Elevation change for the periods
1927-1969, 1969-2002, and 1927-2002 are shown in Figures 4-5a through 4-5c.
The observed morphology changes are discussed in the following paragraphs.
Figure 4-3. Mattituck Inlet, circa 1930 and offshore
elevation contours, 8 December 1927
Figure 4-4. Mattituck Inlet, circa 1930 and offshore
elevation contours, 1969
Chapter 4 Morphology Change, and Channel Shoaling and Migration 111
Figure 4-5a. Mattituck Inlet offshore elevation change, 1927-1969
Figure 4-5b. Mattituck Inlet offshore elevation change, 1969-2002
112 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-5c. Mattituck Inlet offshore elevation change, 1927-2002
From 1927 to 1969, the offshore shoal migrated seaward, and this is
indicated in Figure 4-5a as a landward area of erosion and a seaward area of
deposition east of the inlet. West of the inlet, the main longshore bar migrated
seaward as well. The seaward movement of the longshore bar during this period
may be interpreted as a response to shoreline advance, because the shoreline west
of the inlet advanced as a result of sediment impoundment by the west jetty.
The surface difference of the 1969 and 2002 surveys (Figure 4-5b) shows
that the shoal reached locational equilibrium by 1969, and the main longshore bar
west of the inlet had migrated shoreward. This migration may be attributable to
the steepening of the beach slope over this 33-year period (Batten and
Kraus 2005). This period is also characterized by deposition in front of the
offshore shoal and formation of a new longshore bar adjacent to the east jetty,
which apparently acts to bypass sediment to the downdrift beach.
To further investigate and quantify morphology change of the offshore shoal
and patterns of deposition and erosion near Mattituck Inlet, each grid was sub-
sampled, and TINS were generated from which volume change for the three
periods (1927-1969, 1969-2002, and 1927-2002) was calculated. Figure 4-6
illustrates the areas covered in these calculations. The 8 December 1927 survey
did not fully cover the shoal east of the inlet. Volume change calculations for the
western portion of this feature were conducted, as well as a volume change
calculation for the spatial extent of the feature in the 6-8 October 2002 survey for
the period 1969-2002 (Figure 4-7). Polygons A and B cover the seaward and
landward portions of the offshore shoal area, respectively, and polygon C covers
Chapter 4 Morphology Change, and Channel Shoaling and Migration 113
the area where a longshore bypassing bar has developed. Elevation changes for
the total offshore shoal were calculated from a reference datum of -21.5 ft
NAVD88, taken to be the ambient depth found at the base of the shoal. Table 4-
1 summarizes the results of this analysis.
Figure 4-6. Volume change polygons, east of Mattituck Inlet, with elevation
change 1927-2002
114 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-7. Offshore shoal elevation change, 1969-2002 and Mattituck Inlet
16 April 2003
Table 4-1
Estimated Offshore Volume Change, Mattituck Inlet, 1927-2002
Volume Change (cu yd)
Area 1927-1969 1969-2002 1927-2002
Total study area 155,000 188,000 343,000
Seaward shoaling area (polygon A) 78,000 35,000 113,000
Landward shoaling area (polygon B) negative 45,000 44,500 negative 500
Total shoaling area (polygon A/B) 33,000 78,500 111,500
East bypass bar area (polygon C) 13,500 12,000 25,500
Total offshore shoal area from –21.5 ft NAVD88 13,500
Deposition Rate (cu yd/ year)
Area 1927-1969 1969-2002 1927-2002
Total study area 3,700 5,700 4,700
Seaward shoaling area (polygon A) 2,000 1,000 1,500
Landward shoaling area (polygon B)
negative
1,000 1,000 0
Total shoaling area (polygon A/B) 1,000 2,000 1,500
East bypass bar area (polygon C) 300 400 350
Total offshore shoal area from –21.5 ft NAVD88 500
Chapter 4 Morphology Change, and Channel Shoaling and Migration 115
Estimation of volume change of the offshore shoal for the spatial extents
shown in Figure 4-6 provides insight into the morphology change and patterns
of erosion and deposition for the 75-year period considered. The total study
area gained 343,000 cu yd, yielding a rate of deposition of approximately
4,500 cu yd/year. A considerable portion of this deposition is contributed by
impoundment directly west of the west jetty, as shown in Figure 4-5c. As a
result of seaward migration of the shoal, the seaward area of the shoal (polygon
A) was an area of deposition from 1927 to 2002, and the landward portion
(polygon B) was an area of erosion. Deposition took place in both areas between
1969 and 2002. Polygons A and B are of equal area. Considered collectively,
polygon A+B experienced a net growth of 33,000 cu yd from 1927 to 1969, and
a net growth of 10,000 cu yd for the period 1969-2002.
The rate of deposition for the seaward area was approximately 2,000 cu yd/
year between 1927 and 2002. One thousand cu yd/year of this deposition can be
attributed to migration of the offshore shoal, because the landward area is shown
to be eroding at a rate of 1,000 cu yd/year. Deposition of new material,
therefore, accounts for 1,000 cu yd/year, and can be considered the actual growth
rate of this feature for the period considered. The east bypassing bar is accreting
at a rate of 300 to 400 cu yd/year. The areas of growth are along the seaward
edge of this feature and at the western tip, nearest to the jetty entrance.
Volume change for the total spatial extent of the offshore shoal surveyed on
6-8 October 2002 survey was calculated for the period 1969-2002. The lowest
elevation of either TIN, -21.5 ft NAVD88, was selected as the reference datum.
The calculated volume growth is 13,500 cu yd, and the calculated rate of volume
change is 500 cu yd/year. The volume of the spatial extent of the offshore shoal
shown in Figure 4-7 was calculated to be 460,000 cu yd.
The relative movement of the features offshore of Mattituck Inlet has the
potential to alter the sediment transport pathways. Figure 4-8 shows the center
lines of the offshore shoal in 1927 and 2002. Figure 4-9 shows the relative
location of this feature as well as the relative location of the center lines of the
main longshore bar east of Mattituck Inlet. By 2002, the center line of the main
longshore bar had migrated landward (referenced to its contemporary shoreline),
the shoal has migrated seaward, and the two features no longer directly
connected. The separation of the features resulted in the formation of a secondary
longshore bar adjacent to the east jetty, which may bypass finer sediment to the
downdrift beach.
116 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-8. Mattituck Inlet offshore shoal center lines, 8 December 1927
and 6-8 October 2002
Chapter 4 Morphology Change, and Channel Shoaling and Migration 117
Figure 4-9. Offshore feature center lines, 8 December 1927 and 6-8 October
2002
In summary, the offshore shoal located east of Mattituck Inlet migrated
seaward from 1969 to 2002. This movement, and the landward migration of the
main longshore bar located to the west of the inlet, indicate a change in the
sediment pathways. The increased rate of deposition at the landward area of
shoaling (from –1,000 to +1,000 cu yd/year in polygon B), the decreased rate of
deposition at the seaward area (from 2,000 to 1,000 cu yd/year in polygon A) and
the formation of a bypassing bar directly east of the inlet support this conclusion.
Navigation channel and flood shoal morphology change
This section begins with a review of the natural morphology of Mattituck
Inlet and the modifications introduced by construction of the jetties and by
channel dredging. The evolution, morphology, and migration of the flood shoal
at Mattituck Inlet in response to modifications of the jetties and dredging is
analyzed. For the period 1980 to 2002, volume and elevation changes associated
with dredging activities are calculated. Based upon GIS-generated grids, the
volume changes for three dredging events are estimated. The results are
compared to dredging volumes reported by the New York District. To
understand shoaling patterns within Mattituck Inlet, temporal changes of selected
channel cross sections are analyzed.
118 Chapter 4 Morphology Change, and Channel Shoaling and Migration
The channel condition surveys discussed in this section are referenced to the
mlw datum employed by the surveyors. As discussed in the previous section, the
New York District mlw datum for this time period is believed to be 3.63 ft below
NAVD88.
The dredging history of Mattituck Inlet (Table 2-5) can be consulted to
estimate the rate of sediment accumulation in the navigation channel. Dredging
is usually performed on an as-need basis (every 10 to 15 years), and sometimes
advance dredging is undertaken. These physical and economic constraints
confound interpretation of dredging records and obscure efforts to make a one-to-
one comparison between volume of sediment shoaled and volume of sediment
dredged (Kraus and Rosati 1998). Dredging at Mattituck Inlet has also been
conducted over varying spatial extents. If records are available over a
sufficiently long interval, however, as is the case for Mattituck Inlet,
uncertainties are reduced.
Natural morphology and initial modifications (1891-1914). The Rivers
and Harbors Act of 19 September 1890 authorized a preliminary examination and
survey of Mattituck Inlet that resulted in a favorable recommendation for inlet
modification. The inlet was considered to have modest economic potential and
was seen as a good harbor of refuge. Mattituck Creek in its natural state was
winding and approximately 2-4 ft deep. Figure 4-10 shows the Mattituck Inlet
hwl shoreline of 1891, referenced against the original configuration of the
Federal navigation channel jetty, the present configuration of the Federal
navigation channel, and the original jetty lengths of 1914. Kraus and Rosati
(1997) discuss definitions of the shoreline, including the hwl.
The orientation of Mattituck Inlet in its natural state resembled that of
Goldsmith Inlet prior to the recent dredging of 22-26 March 2004 (Figure 4-106),
where a narrow spit directed to the east, the dominant direction of sediment
transport, developed. Another example of similar morphology on the north shore
of Long Island is found at Stony Brook Harbor, where a large, well-developed
east-directed spit exists (Cooke 1985; Park 1985; Zarillo and Park 1987).
Figure 4-11 shows the hwl shorelines of Mattituck Inlet for the year 1900.
The morphology of Mattituck Inlet has changed significantly, and a west-directed
spit is observed. This west-directed spit is believed to have evolved into what is
now the eastern lobe of the flood shoal. The reversal in the inlet entrance
orientation observed here is consistent with temporary closure and subsequent
reopening of the inlet.
Chapter 4 Morphology Change, and Channel Shoaling and Migration 119
Figure 4-10. Mattituck Inlet orientation, 1891
Figure 4-11. Mattituck Inlet orientation, 1900
120 Chapter 4 Morphology Change, and Channel Shoaling and Migration
New York District (1969) documents that between the 1830s and 1880s, the
entrance to Mattituck Inlet migrated 600 ft to the west, and the spit length was
about 1,000 ft. It is probable that this reported configuration is the result of
lengthening of the spit to the east, making the inlet hydraulically inefficient,
leading to a breach to the west, closer to the inland source channel, and the
present day entrance. Observed after the breach, the channel would have
appeared to migrate west. Figure 4-12 illustrates a hypothesized sequence (a to
d) of spit growth, closure, and reopening that would yield the observed change in
orientation. The sequence resembles one of a number of proposed models
described by FitzGerald et al. (2000).
Figure 4-12. Mattituck Inlet, 1891-1900, hypothesized reorientation
The creation of the Federal navigation channel and construction of the jetties
was approved in the Rivers and Harbor Act of 3 June 1896, and work
commenced in 1901. Figure 4-13 shows the morphology of Mattituck Inlet at
this time. It is assumed that the inlet opening shown here was the result of an
initial partial dredging and that the natural opening to the west was filled in.
The morphology of Mattituck Inlet for 1905 and 1907 is illustrated in
Figure 4-14. Construction of the east jetty was completed in 1906, and a partial
dredging for improvement took place in 1907 (U.S. Engineers Office, First
District 1928). It is not known whether the morphology of 1907 shown in
Figure 4-14 was that prior to or after the partial dredging of 1907. It is believed
that the morphology illustrated was prior to the initial dredging of 1907, because
shoaling is observed along the inside of the west jetty and near the base of the
east jetty.
Chapter 4 Morphology Change, and Channel Shoaling and Migration 121
Figure 4-13. Mattituck Inlet orientation, 1901
Figure 4-14. Mattituck Inlet orientation, 1905-1907
122 Chapter 4 Morphology Change, and Channel Shoaling and Migration
In 1914, the Federal navigation channel was completed by dredging.
Analysis of New York District condition surveys indicate that Mattituck Creek
had been dredged as of a survey dated August 1913 to April 1914. The
morphology of Mattituck Inlet for the period 1913-1914, as listed on the New
York District shoreline survey map, is illustrated in Figure 4-15. Shoals along
the inside of the west jetty had been cleared, shoaling near the base of the east
jetty no longer encroaches upon the Federal navigation channel, and the inlet was
widened along the west bank, directly behind the turn to the east. The
morphology shown here is, therefore, believed to be for a period after the full
dredging of 1914.
Figure 4-15. Mattituck Inlet orientation, 1913/14
Inlet response. This section describes and quantifies sediment shoaling
along the inlet adjacent to the west jetty, sedimentation patterns and shoaling at
the base of the east jetty, the volume and rates of channel infilling, and the area,
volume, and growth of each lobe of the flood shoal for the period 1935 to 1938.
Mattituck Inlet, and the extent of shoaling along the inside of the west jetty, is
shown in Figure 4-16, circa the 1930s (exact year and date unknown). An
apparent landward breach at the base of the east jetty occurred on or around 1935
(Figure 4-17).
Chapter 4 Morphology Change, and Channel Shoaling and Migration 123
Figure 4-16. Mattituck Inlet with shoaling along inside of west jetty, circa 1930s
(exact year and date unknown)
Figure 4-17. Mattituck Inlet east jetty landward breach, 1941
124 Chapter 4 Morphology Change, and Channel Shoaling and Migration
To quantify areal changes of the flood shoal at Mattituck Inlet from 1935 to
1938, each lobe was divided into two sections, the portion that lies below mlw
datum, and the portion that is above mlw. The attached spit, located at the base
of the east jetty and not considered to be a portion of the flood shoal proper, is
also analyzed. Table 4-2 lists the corresponding areas for each portion of the
flood shoal in square feet.
Table 4-2
Mattituck Inlet Flood Shoal Area 1935-1938
Area (sq ft)
Year 1935 1936 1937 1938
West lobe
below mlw 77,000 55,800 66,000 30,100
West lobe
above mlw 48,800 63,200 75,600 81,000
West lobe total 125,800 119,000 141,600 121,100
East lobe
below mlw 107,200 33,400 61,900 66,800
East lobe
above mlw 50,500 21,500 25,200 45,100
East lobe total 157,700 54,900 87,100 111,900
Flood shoal total 283,500 174,400 228,700 233,000
Volumes dredged from Mattituck Inlet during November 1935 to May 1936,
the annual volume of shoaling within Mattituck Inlet, and the volume of channel
infilling for the period 1936 through 1938, were calculated by differencing
bathymetry surfaces digitized from the original survey sheets. Difference
surfaces generated by map calculations of raster grids for each survey are
analyzed to understand the observed volume change. To quantify volume
changes, TIN’s were generated for each condition survey, and the volume for
each TIN was calculated. Volume changes were calculated for the entire study
area and a selected portion of the Federal navigation channel (to estimate the
average rate of channel infilling). The volumes calculated represent those of
sediment in the study area found above a datum located beneath the lowest
elevation contained in the grids considered.
Each lobe of the flood shoal was divided into two sections, the portion
outside the navigation channel and the portion inside the navigation channel.
The volume above a selected datum was then calculated for each TIN. For the
portions outside the navigation channel, a reference datum at a depth of 3 ft mlw
was specified, corresponding to be the average ambient depth outside the
channel. For the portion within the navigation channel, a reference datum at a
depth of 9 ft mlw was specified, corresponding to the average depth after
dredging. The volume and area of each portion of the flood shoal are listed in
Table 4-3. This method does not necessarily consider shoaling along the sloping
walls of the Federal navigation channel, which may introduce error.
Chapter 4 Morphology Change, and Channel Shoaling and Migration 125
Table 4-3
Estimated Mattituck Inlet Flood Shoal Volumes and Areas,
1935-1938
Volume (cu yd)
Feature 1935 1936 1937 1938
West lobe
outside channel 11,600 19,400 23,400 16,100
West lobe
inside channel 7,100 0 3,100 6,400
West lobe total 18,700 19,400 26,500 22,500
East lobe
outside channel 9,800 5,800 5,700 9,300
East lobe
inside channel 17,600 0 3,400 4,200
East Lobe total 27,400 5,800 9,100 13,500
Flood shoal total 46,100 25,200 35,600 36,000
Area (sq ft)
West lobe
outside channel 102,800 109,200 113,600 86,200
West lobe
inside channel 25,600 0 14,000 17,200
West lobe total 128,400 109,200 127,600 103,400
East lobe
outside channel 90,000 56,300 53,600 80,900
East lobe
inside channel 58,100 0 24,100 28,200
East lobe total 148,100 56,300 77,700 109,100
Flood shoal total 276,500 165,500 205,300 212,500
The original navigation project authorized the jetties to the 9-ft mlw depth
contour (Ralston 1928). The authorized jetty lengths, 1,030 ft for the west jetty
and 775 ft for the east jetty, did not adequately protect the inlet from shoaling.
Sediment intrusion from the west to east, associated with the predominant
direction of longshore transport, augmented by storms from the northwest
quadrant, resulted in rapid shoaling within the channel along the west jetty. In
addition, the shoreline directly east of Mattituck Inlet receded rapidly, causing a
landward breach at the base of the east jetty sometime in the mid-1930s.
Evidence of this landward breach can be seen in Figure 4-17 (circa 1941).
The initial new work dredging of the Federal navigation channel at Mattituck
Inlet was completed in 1914. From June to November 1921, the first
maintenance dredging occurred, removing 13,498 cu yd of sediment. Given the
fact that the next dredging occurred only 2 years later, this dredging is considered
to be an emergency dredging to restore the Federal navigation channel to project
dimensions. Visual inspection of a New York District condition survey dated
30 April 1920 confirms that the channel had greatly shoaled and was nearly non-
navigable.
126 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-18a shows the approximate hwl position in 1927, indicating
considerable accretion on the west side of Mattituck Inlet. Dredging from
August to September 1923 removed 49,168 cu yd of sediment. Of this dredging
and the dredging of September-October 1927, Ralston (1928) states that the
removed sediment was “principally from the entrance channel between the
jetties.” Newly dredged channels will often be subject to sediment slumping, in
which sediment falls into a channel as the inlet trends towards equilibrium
morphology. Given the large volumes dredged in the period 1921 – 1927, it is
hypothesized that sediment slumping is responsible for a portion of the sediment
dredged, and that the volumes dredged during this early period cannot be totally
attributable to longshore sediment transport rates for this area.
Condition surveys indicates that the Federal navigation channel had
narrowed to less than 50 ft at the base of the east jetty by May 1925, and that
controlling depths of the channel had decreased to 5 ft mlw by May 1925, to 3 ft
by June 1926, and to 2.5 ft by August 1927 (Ralston 1928). Preliminary
examination (submitted 29 April 1927) and subsequent survey (submitted
22 June 1928), concluded that “shoaling is caused mainly by heavy material
(sand and gravel) being driven into the inlet by the action of storms from the
northwest quadrant, to which the inlet is directly exposed” (Ralston 1928). The
report notes that sand fences had been erected with no appreciable effect, which
precludes wind-blown sand as a significant sediment source (or that the sand
fencing was ineffective). These surveys produced a recommendation that the
west jetty be extended seaward 350 ft, or to the 12-to-15 ft mlw depth contour.
The survey also recommends a possible further seaward extension of 150 ft for
the west jetty and a seaward extension of 300 ft for the east jetty “if required and
conditions indicate” (Ralston 1928). The Rivers and Harbor Act of 30 August
1935 authorized a 250-ft seaward extension of the west jetty.
The dredging from September to October 1927 restored Mattituck Inlet to the
specified project depth. Figure 4-18a shows channel elevations, and Figure 4-
18b shows the areal extent of the flood shoal, for 23 September 1935, 8 years
after this dredging. The east and west lobes of the flood shoal have joined, and
the controlling depth is 2 ft mlw. At this time, the Federal navigation channel
was presumably navigable only during times of high water. Infilling along the
insides of both jetties created significant tracts of dry shoals. The condition
survey of 23 September 1935 did not fully record the shoreline position. The
landward breach at the base of the east jetty can be discerned. Evidence of this
breach becomes clearer in successive surveys. The shoreline fragments for this
period that were recorded are indicated in black, referenced against the hwl
shoreline of 8 December 1927. A portion of this area, within the channel at the
base of the east jetty, appears to be below mlw, further indicating that the breach
had begun to form at this point.
Chapter 4 Morphology Change, and Channel Shoaling and Migration 127
Figure 4-18a. Mattituck Inlet channel elevation, 1935
Figure 4-18b. Mattituck Inlet flood shoal area, 1935
128 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Channel elevations and hwl location for 4 May 1936, immediately after the
dredging of November 1935 to May 1936, are shown in Figure 4-19a. The areal
extent of the flood shoal is illustrated in Figure 4-19b. The shoreline of 4 May
1936 is illustrated in Figure 4-19a, referenced against the shoreline of
8 December 1927, and the landward breach near the base of the east jetty is
clearly apparent. It is inferred that sediment was transported to the east bank by
landward bypassing during times of high tide and storms. It is appropriate to
consider this feature a spit onto which the east lobe of the flood shoal attaches
itself. Because this spit is dredged only if it encroaches upon the Federal
navigation channel, a portion was not removed. This portion remains in the
system and has evolved into what is considered as the modern-day flood shoal.
The dredging of November 1935 to May 1936 restored the Federal navigation
channel to project depth. Figure 4-19c plots the net change in elevation as a
result of the maintenance dredging of November 1935 to May 1936. In some
areas, the elevation change is extreme. Near the base of the jetties, the channel
has a tendency to migrate to the west, and dredging served to reposition the
navigation channel back to project specifications. Dredging reduced elevation by
16 ft in the area where the flood shoal was removed. An increase of 12 ft
occurred where landward bypassing deposited sediment along the inside of the
base of the east jetty. An increase of 8 ft occurred near the west bank of the
channel, presumably a result of repositioning the channel.
Figure 4-19a. Mattituck Inlet channel elevation, 4 May 1936
Chapter 4 Morphology Change, and Channel Shoaling and Migration 129
Figure 4-19b. Mattituck Inlet flood shoal area, 4 May 1936
Figure 4-19c. Channel elevation change, 1935 to 4 May 1936
130 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Dredging records indicate that 50,785 cu yd of sediment was removed during
the period November 1935 to May 1936. The volume change for the total study
area below mlw is here calculated to be 44,000 cu yd. The volume change for a
selected portion of the Federal navigation channel below mlw, as indicated in
Figure 4-20, was calculated to be 25,500 cu yd. The average pre-dredging depth
for the Federal navigation channel was calculated to be 3.2 ft mlw, and the
average depth after dredging was calculated to be 9 ft, a figure which conforms
to the specified project depth of 7 ft mlw with 2 ft allowable overdraft. The
volume change for what was defined to be the flood shoal proper, as outlined in
Figure 4-19a and 4-19b, was calculated to be 20,100 cu yd. The lobes of the
flood shoal within the Federal navigation channel were removed, as were a
considerable portion of the east lobe outside the channel and a small portion of
the west lobe outside the channel.
Figure 4-20. Federal navigation channel study area
Chapter 4 Morphology Change, and Channel Shoaling and Migration 131
Channel elevations for 3 July 1937 are shown in Figure 4-21a. The areal
extent of the flood shoal at this time is shown in Figure 4-21b, and channel
elevation change between 4 May 1936 and 3 July 1937 is plotted in Figure 4-21c.
For this 14-month period, the net volume change for the study area was
calculated to be 12,000 cu yd, yielding an annual sediment accumulation rate of
10,500 cu yd/year. The portion of the Federal navigation channel considered was
calculated to have 5,200 cu yd of infilling, for an average channel infilling rate of
4,500 cu yd/year for the period. The area of the Federal navigation channel
considered is 194,000 sq ft. The average depth of the channel for 3 July 1937
was calculated to be 7.8 ft. The flood shoal was calculated to have grown from
25,200 to 35,600 cu yd.
Figure 4-21a. Mattituck Inlet channel elevation, 3 July 1937
132 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-21b. Mattituck Inlet flood shoal area, 3 July 1937
Figure 4-21c. Channel elevation change, 4 May 1936 to 3 July 1937
Chapter 4 Morphology Change, and Channel Shoaling and Migration 133
Figure 4-22a shows channel elevations for July 1938 (exact date not
available), and the areal extent of the flood shoal is illustrated in Figure 4-22b.
Channel elevation changes between 4 May 1936 and July 1938 are plotted in
Figure 4-22c. For the 26-month period, the net volume change for the study area
was calculated to be 13,882 cu yd, yielding an annual sediment accumulation rate
of 6,500 cu yd/year. The portion of the Federal navigation channel considered
was calculated to have 6,600 cu yd of infilling for the 26-month period, for an
average channel infilling rate of 3,000 cu yd/year for the period.
The average depth of the Federal navigation channel for July 1938 was
calculated to be 7.5 ft. The flood shoal was calculated to have grown by only
400 cu yd during this period. This small volume change can be attributed to the
fact that the condition survey of 1938 did not fully record elevations along the
west side of the inlet. The area of elevations not recorded can be discerned by
comparing the survey extent shown in Figure 4-40 to that of prior condition
surveys. The extent of this area is approximately 26,000 sq ft. Because the area
not surveyed is dry shoal, the depth was taken to be at least 7.5 ft, based on the
morphology of 3 July 1937 and the ambient depth at this location, resulting in a
volume of shoaling that is estimated to be at least 7,000 cu yd. This figure, in
addition to the 400 cu yd calculated, yields an estimated growth of the total flood
shoal of 7,400 cu yd.
Figure 4-22a. Mattituck Inlet channel elevation, 1938
134 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-22b. Mattituck Inlet flood shoal area, 1938
Figure 4-22c. Channel elevation change, 4 May 1936 to 1938
Chapter 4 Morphology Change, and Channel Shoaling and Migration 135
Changes in planform morphology for the west and east lobes of the flood
shoal for the period 1936-1938 are illustrated in Figures 4-23a and 4-23b. The
observed morphology change for both lobes may indicate the transport of
sediment from the west lobe to the east lobe, further into the channel.
Figure 4-23a. West lobe morphology change, 1936–1938
Figure 4-23b. East lobe morphology change, 1936–1938
136 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Landward breaching, spit formation, and jetty modification. In response
to rapid sediment accumulation, the west jetty at Mattituck Inlet was repaired and
extended seaward 250 ft from October 1937 to September 1938 (Figure 4-24 and
Table 2-6). Prior to this, on or before 1935, a breach next to the east jetty
occurred as the shoreline receded. Figure 4-25 shows the shoreward breach and
the approximate hwl recession from 1927 to 1941. Contour elevations are drawn
to reveal shoaling of sediment within the inlet from 1935 to 1938. The condition
survey of 1938 did not contain a shoreline (panel e), so it cannot be shown. The
1941 shoreline (panel f) was derived from an 1941 aerial photograph and should
be regarded as an estimate. This series of figures documents the widening breach.
The contour elevations illustrate the rapid buildup of sediment, where the inlet,
directly inside of the east jetty has negative elevations in 1935 and positive
elevations in 1936.
Figure 4-24. Mattituck Inlet west jetty seaward extension, 1938
The dredging of July to August 1938 removed 18,312 cu yd of sediment.
Prior to this, the November 1935 to May 1936 dredging removed a large volume
of sediment (50,785 cu yd) that restored the Federal navigation channel to project
depth. As of 1938, the large volume of exposed shoal along the inside of the
west jetty was still present (Figure 4-25). This exposed shoal is not apparent in
the aerial photograph of 1941 (Figure 4-17) so it is reasonable to believe that the
dredging of July–August 1938 removed a large portion of the west lobe of the
flood shoal.
Chapter 4 Morphology Change, and Channel Shoaling and Migration 137
The seaward extension of the west jetty reduced sediment intrusion into the
inlet from the west. Dredging of 53,893 cu yd and the repair and 280-ft landward
extension of the east jetty took place between August-November 1946. Post-
dredging surveys indicate that the west shoal was dredged in its entirety by this
time. The dredging of September – November 1946 extended beyond the area of
normal dredging (section A in Figure 2-7), and included a portion of Mattituck
Creek (approximately half of section B in Figure 2-7). However, only the
portion of the east lobe of the flood shoal that encroached in the Federal
navigation channel was dredged. The exposed portion of this lobe, a westward-
directed spit, is not considered to be a part of the flood shoal because it was
formed from landward bypassing. This spit has remained nearly stable from
1950 until present and can be traced to the inlet morphology exhibited in 1891
(Figure 4-10), prior to placement of the jetties.
(a) 8 December 1927 (b) 23 September 1935
(c) 4 May 1936 (d) 3 July 1937
(e) 1938 (f) 1941
Figure 4-25. Shoreline recession and east jetty landward breach 1927 to 1941
138 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figures 4-26a and 4-26b illustrate the morphology of this spit in 1891, when
Mattituck Inlet was in a natural state, to 1955. The spit experienced rapid growth
due to the landward breach in the 1930s. After the landward extension of the east
jetty in 1946, this spit began to migrate south and east under wave attack and due
to transport by the flood current. Panel d of Figure 4-26b shows the spit in 1955,
when it had begun migrating. The migration of this spit and its evolution into the
present-day flood shoal are analyzed next.
(b) 1907
Prior to Jetty Construction
(a) 1891
Prior to Jetty Construction
(c) 1914
After Jetty Construction
(d) 8 December 1927
After Jetty Construction
(b) 1907
Prior to Jetty Construction
(a) 1891
Prior to Jetty Construction
(c) 1914
After Jetty Construction
(d) 8 December 1927
After Jetty Construction
Figure 4-26a. Mattituck Inlet east bank spit morphology, 1891-1927, with jetty
configuration of 1914 included for reference
Chapter 4 Morphology Change, and Channel Shoaling and Migration 139
(a) 23 September 1935
After Shoreward Breach (b) 3 July 1937
After Shoreward Breach
(c) 1941
After Shoreward Breach
(d) 1955
After East Jetty Repair and
Shoreward extension
(a) 23 September 1935
After Shoreward Breach (b) 3 July 1937
After Shoreward Breach
(c) 1941
After Shoreward Breach
(d) 1955
After East Jetty Repair and
Shoreward extension
Figure 4-26b. Mattituck Inlet east bank spit morphology, 1935-1955, with jetty
configuration of 1914 and 1946 included for reference
Condition survey maps indicate that the present configuration of the Federal
navigation channel was introduced, and maintenance dredging took place, during
the period October-November 1950 (Tables 2-5 and 2-6). The post- dredging
survey of September-November 1946 and the pre-dredging survey of
4-6 October 1950 indicate that much of the east bank spit was left intact.
Removal of the portion of the flood shoal that was located within the location of
the new navigation channel apparently involved the dredging of an estimated
10,000-12,000 cu yd of sediment. This value accounts for approximately 40 to
50 percent of the 22,913 cu yd of sediment dredged in October–September 1950.
Figure 4-27 illustrates the configuration of the Federal navigation channel prior
to and after 1950.
140 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-27. Mattituck Inlet Federal navigation channel configuration, prior to
and after October – November 1950
Repositioning of the Federal navigation channel increased the maximum
channel cross-section width to approximately 210 ft. The repairs of
October 1937 - August 1938 and August-September 1946, together with the
clearing of the west flood shoal and the introduction of the present navigation
channel position in October-November 1950, brought the configuration of
Mattituck Inlet close to its present configuration.
The dredging of August–September 1955 removed 31,552 cu yd of sediment.
Dredging took place only in section A (Figure 2-7), from the channel entrance to
the location of the east flood shoal. The dredging of August-October 1961
removed 43,550 cu yd of sediment. The extent of this dredging included section
A and all of section B (Figure 2-7). Elevation change in section A for this
dredging is discussed in the next section of this chapter.
During September–October 1965, a one-time dredging was performed to
create a Federal anchorage at the head of Mattituck Creek, in addition to the
dredging of the entrance of the Federal navigation channel. Areas dredged at this
time are indicated in Figure 4-28. A total 47,265 cu yd of sediment was dredged.
As indicated in Figure 4-28, only portions of section A and of section B adjacent
to the flood shoal were dredged, removing 6,285 cu yd of sediment. The
remaining 40,980 cu yd of sediment was dredged from the Federal anchorage and
southern section of Mattituck Creek.
Chapter 4 Morphology Change, and Channel Shoaling and Migration 141
Figure 4-28. Federal navigation channel and Federal anchorage
dredging areas, September – October 1965
Figures 4-29a through 4-29l show Mattituck Inlet at different times from
1930 to April 2004. Figure 4-29d shows Mattituck Inlet on 11 May 1955,
immediately prior to a maintenance dredging. According to the conditions
surveys of 1946 and 1950, sediment dredged during these periods was placed to
nourish the beach east of Mattituck Inlet. The 1955 aerial photograph indicates
that width of the beach directly adjacent to the east jetty had increased by
approximately 50 ft (as compared to 1941).
The migration of the attached formation from 1941 to present can be seen in
this series of figures. The formation appears to have begun migrating after 1950,
apparently in response to the prior jetty modifications. The post-dredging survey
of 7-8 November 1950 shows the now-truncated formation to be oriented
perpendicular to the east jetty and generally oriented along an east-west axis, as it
was in 1941. The orientation of this formation in 1976 and thereafter is
approximately along a north-south axis. Subsequent aerial photographs show
that this formation continued to migrate further into the inlet. Waves and the
flood current are presumed to have caused this formation to migrate, and because
much of this formation presently lies below mlw, it can now be considered to be
a flood shoal.
The morphology of Mattituck Inlet on 16 April 2003, 11 months prior to the
recent dredging of 17-24 March 2004, is shown in Figure 4-29k. Figure 4-29l
shows the morphology of Mattituck Inlet on 15 April 2004, immediately after
this dredging.
142 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-29a. Mattituck Inlet, circa 1930
Figure 4-29b. Mattituck Inlet, 1938 (exact month and day unknown)
Chapter 4 Morphology Change, and Channel Shoaling and Migration 143
Figure 4-29c. Mattituck Inlet, 1941(exact month and day unknown)
Figure 4-29d. Mattituck Inlet, 11 May 1955
144 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-29e. Mattituck Inlet, 1 April 1964
Figure 4-29f. Mattituck Inlet, 25 April 1969
Chapter 4 Morphology Change, and Channel Shoaling and Migration 145
Figure 4-29g. Mattituck Inlet, 6 April 1976
Figure 4-29h. Mattituck Inlet, 23 March 1980
146 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-29i. Mattituck Inlet, 5 April 1993
Figure 4-29j. Mattituck Inlet, 26-30 April 2001
Chapter 4 Morphology Change, and Channel Shoaling and Migration 147
Figure 4-29k. Mattituck Inlet, 16 April 2003
Figure 4-29l. Mattituck Inlet, 15 April 2004
148 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Commercial mining activities. Mattituck Inlet has been the site of
considerable commercial mining. Mining of the Federal navigation channel,
under Federal permit, and mining of the beach directly west of the west jetty
under local permit, removed a large volume of sediment from this system from
1920 to 1977. These activities, and their possible implications on sediment
transport at Mattituck Inlet are discussed here.
In the course of the present study, the archive of New York District dredging
permits was accessed to investigate permitted commercial dredging for gravel
and sand within the limits of the Federal navigation project (Table 2-7). The
New York District could only issue permits for dredging within the Federal
navigation project, because adjacent submerged land falls under jurisdiction of
the State of New York, a point repeatedly raised in local agency review of the
permit requests. Permit applications and associated documentation of New York
District actions were found for the interval 1925 to 1948 and primarily concerned
shoaling areas adjacent to the west jetty. During this interval, the Federal
navigation channel was configured such that it abutted the west bank of
Mattituck Inlet at the base of the west jetty (see Figure 4-27).
Federal permits allowed dredging to depths ranging from 7 to 20 ft mlw.
Most of the permit applicants did not complete planned work, as indicated by
requests for extensions or renewals, or by comments from New York District
inspectors. Therefore, it is uncertain how much dredging occurred for
commercial use, although it is expected to have been intermittent, but substantial
at times.
The functional duration of commercial mining activities is not known, and
the Federal permits provide no information on the volumes dredged. However,
because of the asphalt-handling infrastructure that was present near the inlet,
there is evidence of a robust mining industry at Mattituck Inlet for a long span of
time. Ralston (1928) states that the sand and gravel industry at Mattituck Inlet
could dredge “50 cu yd, daily, of sand and gravel from between the jetties at the
entrance to the harbor, under permit from the War Department, and its
transportation to the south end of the harbor for manufacture into concrete tile.”
Three permits were issued prior to the Ralston (1928) report. Two of these
(J.H. Rambo, and Northport Sand and Gravel) apparently indicate offsite disposal
of the dredged material, and the third (C. H. Benjamin) indicates disposal on the
Wickert estate, located adjacent to the area of mining. It is, therefore, apparent
that the activities referred to by Ralston (1928), which note “transportation to the
south end of the harbor,” are different than those referred to in the Federal
dredging permits.
The existence of a robust mining industry at Mattituck Inlet is further
evidenced in New York District condition surveys, which document physical
plants of sand and gravel companies. The condition survey map dated 20 May
1965 notes the existence of an abandoned “Sand Plant” on the west bank of
Mattituck Creek. The condition survey map dated 20 May 1965 notes the
physical plants of Asphalts, Inc. and the Gotham Sand and Gravel Company,
both near the area of mining. The condition survey map dated 27 July 1971
notes the physical plant of the New Sand and Gravel Company near this same
location. The locations of the physical plants are shown in Figure 4-30.
Chapter 4 Morphology Change, and Channel Shoaling and Migration 149
Figure 4-30. Mining related companies and locations at Mattituck Inlet
The only estimated volume information is that given by Ralston (1928) in
reference to “50 cu yd, daily.” This figure translates to 10,000 cu yd annually
(for 200 working days). Known Federal dredging permits cover a time period of
approximately 30 years. Given the evidence of commercial activity associated
with sediment mining, the possibility of substantial undocumented mining at
Mattituck Inlet is strong, as is the evidence that mining practices continued
beyond the 1940s. The authors of the present study therefore estimate that from
250,000 to 500,000 cu yd of sediment was removed from Mattituck Inlet from
1920 to 1970.
The extent of sediment mining on the beach directly west of the west jetty is
unclear as well. Schubel (1976) documents mining of sand and gravel from the
beach directly west of the west jetty for the period 1960-1975, under permit of
the Mattituck Park District (Table 2-8). The area of permitted removal was
bounded by the hwl, a line “parallel to and 25 yards from the west jetty” and a
second parallel line located near a refreshment stand (Schubel 1976). According
to local sources, these activities have continued “on and off” for a period of over
50 years, up to 1976.1 Analysis of aerial photographs from 11 May 1955 (Figure
4-29d) and 1 April 1964 (Figure 4-29e) support the presence of mining activities
at this location prior to 1960. The noted area would normally experience a net
gain of sediment through jetty impoundment, and the aerial photographs indicate
shoreline recession.
1 Personal Communication, 30 August 2004, Mr. Frank Murphy, Mattituck Park District
Supervisor (retired).
150 Chapter 4 Morphology Change, and Channel Shoaling and Migration
The authors of the present study estimate that these mining activities
removed 260,000 to 380,000 cu yd from the system. The consequence of this
mining on sediment accumulation within Mattituck Inlet can be seen in the
dredging records (Table 2-5), where a substantial decrease in dredged volume
within the channel is observed after 1965. Cessation of these mining activities
can also, in turn, be expected to eventually increase sediment accumulation rates
within Mattituck Inlet. Impoundment west of the west jetty is observed to have
increased in recent years, and the shoreline there has advanced (see Figures 4-
29h through 4-29l; Batten and Kraus 2005). Sediment accumulation rates can be
expected to increase significantly when the west jetty has reached impoundment
capacity.
Elevation change and dredging volume. In its present condition, Mattituck
Inlet is a hydraulically efficient channel that experiences small rates of sediment
accumulation. Gradual shoaling within the Federal navigation channel
eventually leads to constriction, and this shoaling is the main requirement for
periodic dredging, jetty repair, and jetty extension. The good performance of the
Mattituck Inlet navigation project in its present condition is largely the result of
proper maintenance and jetties of adequate length. Sand and gravel mining that
occurred directly west of the inlet which served to keep the volume of sediment
located there below the impoundment capacity of the west jetty, is also a
significant factor. Dredging records (Table 2-5) indicate that the Federal
navigation channel at Mattituck Inlet accumulated sediment at a rate of 1,000-
2,000 cu yd/year from 1965 to 1990. The repair of the west jetty in 1975 may
partially explain the decrease in accumulation rate. (The west jetty was last
repaired in 1996.) Improvements in dredging technology may also account for
the smaller volumes that have been dredged in recent years, where the channel is
more accurately dredged to the project depth of 7 ft mlw with 2-ft overdraft.
The volume dredged in August to October 1961 was 43,550 cu yd. This
volume resulted in average channel depths of about 10 to 11 ft mlw, 1 to 2 ft
greater than the authorized depth of 7 ft mlw with 2 ft advance dredging. The
volume change for the September to October 1965 dredging was not calculated
because a full pre-dredging condition survey was not available. The channel
depth observed after dredging in May 1980 and October 1990 for this same
location is 9 ft mlw, equal to the authorized project depth of 7 ft mlw with 2-ft
advance dredging.
Maintenance dredging of Mattituck Inlet was performed in May 1980 and
October 1990 (Table 2-5). The most recent maintenance dredging of the channel
took place on 17-24 March 2004. Dredging volume changes for years 1961,
1980, and 1990 are analyzed here. The dredging of 1965 included section B as
shown in Figure 2-7 as well as section A. The dredgings of 1980 and 1990
covered only section A, the area of typical dredging. Figure 4-31a plots channel
elevations for June 1961, prior to dredging, and Figure 4-31b shows channel
elevations for September 1961, immediately after dredging. Figure 4-31c plots
the net change in elevation as a result of the maintenance dredging of September
1961. Figures 4-32a through 3-32c show channel elevation and elevation change
for the maintenance dredging of 1980. Figures 3-33a through 3-33c show
channel elevation and elevation change for the maintenance dredging of 1990.
The shoaling patterns observed in these figures are largely the same as those
that followed the 1946 landward extension of the east jetty, though the rate of
Chapter 4 Morphology Change, and Channel Shoaling and Migration 151
sediment accumulation diminished greatly after 1965. Shoaling now occurs
mainly along the east bank, directly behind the shoreward end of the east jetty.
Shoaling is also observed along the west bank, directly opposite the main flood
shoal and alongside the seaward tip of the west jetty. Based on the amount of
sediment dredged from these locations (Figures 4-31c, 4-32c and 4-33c),
sediment accumulates at these locations along the sloped walls of the channel,
causing the channel to become increasingly constricted. Shoaling also occurs at
the mouth of the inlet, where sediment accumulates at the bottom of the channel
(channel infilling). Dredging serves to deepen the channel, as well as widen it in
areas where bank encroachment constricts the channel.
Figure 4-31a. Channel elevation, June 1961 (pre-dredging)
152 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-31b. Channel elevation, September 1961 (post-dredging)
Figure 4-31c. Channel elevation change , June 1961 - September 1961
Chapter 4 Morphology Change, and Channel Shoaling and Migration 153
Figure 4-32a. Channel elevation, January 1980 (pre-dredging)
Figure 4-32b. Channel elevation, May 1980 (post-dredging)
154 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-32c. Channel elevation change, January 1980 - May 1980
Figure 4-33a. Channel elevation, September 1990 (pre-dredging)
Chapter 4 Morphology Change, and Channel Shoaling and Migration 155
Figure 4-33b. Channel elevation, October 1990 (post-dredging)
Figure 4-33c. Channel elevation change, September 1990 - October 1990
156 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Volumes dredged from the navigation channel were calculated by
differencing bathymetry surfaces. A TIN was generated for each condition
survey, and the volume for each TIN was then calculated. The volumes
calculated represent the volumes of sediment in the study area found above a
datum located beneath the lowest elevation found. Because ArcView GIS
introduces surface area variation in generating grids, the surface areas compared
were normalized to represent equal surface areas. The volume of the post-
dredging grid was divided by its planimetric surface area, yielding an average
height above the reference datum. This height was then multiplied by the
planimetric surface area of the pre-dredging grid. The total volume of a post-
dredging TIN was then subtracted from its corresponding pre-dredging TIN.
Results of these calculations are listed in Table 4-4 and compared to the
reported volumes dredged. The data indicate an accumulation rate of 1,000 to
2,000 cu yd/year for the period following the jetty repairs of 1975 for the area
considered. Good agreement is found between calculated and reported volume
for January 1980 to May 1980. Agreement between June 1961 and September
1961 is reasonable as well. The dredging of September 1961 included a section
of the channel not normally dredged. The volumes dredged from this extra
portion are not, however, expected to be large. Given this fact, the calculated
volume, which is less than the reported volume, is considered to be reasonably
accurate. The calculated volume for the September 1980 to October 1990 is only
50 percent of the reported volume. The cause of this discrepancy is unknown.
Table 4-4
Calculated Versus Measured Dredging Volumes, Mattituck Inlet
Channel
Pre-Dredging Date Post-Dredging Date
Calculated Volume
(cu yd)
Reported Volume
(cu yd)
June 1961 September 1961 40, 473 43,550
January 1980 May 1980 26,459 24,137
September 1990 October 1990 26,595 13,241
Table 4-5 provides estimated sediment accumulation rates at Mattituck Inlet
for selected periods. Certain periods are not included, in instances when the
extent or purpose of the dredging is beyond normal maintenance (as with the
October–November 1950, which served to reposition the Federal navigation
channel).
Chapter 4 Morphology Change, and Channel Shoaling and Migration 157
Table 4-5
Estimated Sediment Accumulation Rates,
Mattituck Inlet Federal Navigation Channel
Period Rate (cu/yd year)
1914 – August 1923* 7,000
September 1923 – September 1927 12,000
October 1927 – November 1935 6,500
May 1936 – July 1938 8,500
August 1938 – September 1946 6,500
November 1950 – August 1955 7,000
September 1955 – August 1961 7,000
October 1961 – September 1965 1,500
October 1965 – May 1980 1,500
May 1980 – October 1990 1,300
October 1990 – March 2004 1,000
* Includes dredging of June - November 1921
The average sediment accumulation rate from 1914 to 1946, the period prior
to the modification of both jetties, is 8,100 cu yd/year and the range is 6,500 to
12,000 cu yd/year. The previous repairs and extensions appear to have greatly
mitigated shoaling along the west jetty, and a reduction in the sediment
accumulation rate is expected after the major rehabilitation of 1946. The
continued high rate indicated from 1946 to 1961 is interpreted as a transitional
period containing adjustments of the morphology of Mattituck Inlet to a new
hydrodynamic equilibrium condition. The decrease in rates for the period 1961
to the present is considerable. The efficiency of the current Federal navigation
project and the mining of sediment directly west of the jetty are identified as the
major factors in the observed decrease.
Seventeen condition survey maps from the years 1969 to 2003 were
digitized, and quantitative analysis of sediment deposition within the Mattituck
Inlet navigation channel was attempted through surface differencing. It was
found that the annual volume difference between successive condition surveys
was too small to detect because the volume error was three to six times the
annual volume change (1,000 to 2,000 cu yd). The surface areas analyzed
measure approximately 60,000 sq yd. A survey error of 0.33 ft, or 0.1 yd, yields
a volume error of +/- 6,000 cu yd. The volumes obtained based on the post-
dredging condition surveys are considered reliable because of the large change
relative to the pre-dredging surveys.
The difference maps generated do, however, provide qualitative information
on the location and persistence of shoaling within the channel. Sediment
accumulation within the channel appears to be constant and evenly distributed,
with the exception of the inlet entrance, where considerable shoaling is observed
along the west jetty. Near the shoreward end, areas of scour and shoaling are
apparent. Figures 4-43a through 4-34e illustrate elevation changes from May
1980 (immediately after a dredging) through October 1990.
158 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-34a. Channel elevation change, May 1980 to August 1983
Figure 4-34b. Channel elevation change, May 1980 to June 1985
Chapter 4 Morphology Change, and Channel Shoaling and Migration 159
Figure 4-34c. Channel elevation change, May 1980 to September 1987
Figure 4-34d. Channel elevation change, May 1980 to June 1988
160 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-34e. Channel elevation change, May 1980 to October 1989
The total volume of sediment that accumulated within the channel for the
period from October 1990 to January 2002 was calculated to be 24,600 cu yd.
This figure is considered reasonable in indicating an annual deposition rate
within the inlet of 2,000 cu yd/year. The grids analyzed in this calculation do not
cover the full flood shoal (Figure 4-35), so the actual amount accumulated may
be larger. The survey of January 2002 did not fully capture the flood shoal,
presumably because it was inaccessible. Scour along the east jetty can also be
seen.
Chapter 4 Morphology Change, and Channel Shoaling and Migration 161
Figure 4-35. Channel elevation change, October 1990 to January 2002
A post-dredging condition survey following the recent dredging of
17-24 March 2004 was not available at the time of this writing. Figure 4-36
compares the shoreline of Mattituck Inlet of 16 April 2003 (11 months prior to
the most recent dredging) to the shoreline of 15 April 2004 (immediately after
dredging). The volume of 13,786 cu yd was removed from Mattituck Inlet and
the sediment was placed on the beach directly east of the inlet. The observed
morphology change clearly illustrates the placement of this sediment and
dredging of the main area of shoaling on the east bank, as well as the dredging of
the area of secondary shoaling in the west bank.
162 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-36. Mattituck Inlet shoreline, pre- and post-dredging, 16 April 2003 and
15 April 2004
East bank spit migration
Migration of the east bank spit from 1941 to present is summarized in
Figures 4-37a and 4-37b. The orientation of the axis of this formation rotated
from east-west to north-south between 1941 and 1969. This reorientation took
the formation from the end of the east jetty to the mouth of Mattituck Creek.
Estimates of the center lines for the formation for each photograph are
approximated in Figure 4-37a to illustrate the rotation and reorientation. The spit
began to migrate after 1969. It migrated 260 ft from 1969 to 1976, and 80 ft
from 1976 to 1980, with corresponding rates of 37 and 20 ft/year, respectively.
After 1980, the formation appears to have reached locational equilibrium, which
may indicate the limit of transporting capacity of the flood current. However,
this feature could continue to grow into the channel if sediment is supplied to it.
Chapter 4 Morphology Change, and Channel Shoaling and Migration 163
1941
Apr 1969
Apr 1976
May 1955
Apr 1964
1941
Apr 1969
Apr 1976
May 1955
Apr 1964
Figure 4-37a. East bank spit migration, 1941-1976
Apr 2003
Apr 1976
Mar 1980 Apr 1993
Apr 2003
Apr 1976
Mar 1980 Apr 1993
Figure 4-37b. East flood shoal migration, 1976-2003
164 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Bank encroachment analysis
To further quantify the shoaling patterns within Mattituck Inlet, temporal
changes in channel width were analyzed. Three cross sections were extracted
from the 1980 to 2002 conditions surveys. The locations of these cross sections
are shown in Figure 4-38. The temporal changes in cross-sections A and B are
analyzed for the period 1980 to 1990, because the data from this period provide
the best spatial and temporal coverage. Cross-section C was analyzed for the
period 1990 to 2002 to illustrate recent and current morphology changes in this
area.
Figure 4-38. Mattituck Inlet channel cross sections
Figure 4-39a shows changes in cross-section A from May 1980 to March
1990, and Figure 4-39b shows changes in cross-section B for the same period.
Because these cross sections are not surveyed at identical locations, there is
spatial variation between annual surveys. Some of the morphology changes
indicated are within survey error. Trends of channel infilling and bank
encroachment can be seen over the periods considered. Cross-section A was
surveyed for 6 years, and cross-section B was surveyed for only 4 years because
there were no surveys near this location in June 1985 and September 1987.
Cross-section A is located approximately 150 ft north of the east flood shoal, and
Chapter 4 Morphology Change, and Channel Shoaling and Migration 165
cross-section B is directly adjacent to, and partially cuts through the east flood
shoal.
Cross-section A shows areas of scour on the west side of Mattituck Inlet,
with channel depths averaging 15 ft. A high degree of variability is indicated.
The variability may be the result of differences in survey position, although it is
possible that these changes reflect episodes of scour at specific times. Bank
encroachment can be seen on the east wall of the navigation channel. Referenced
to a depth of 5 ft mlw, sediment accumulation has added approximately 25 ft to
the eastern wall of the navigation channel over the 10-year period. This estimate
seems reasonable and is supported by the trend over time seen in this figure.
Referenced from the center of this cross section, the figure indicates that channel
infilling added 1.5 ft of sediment to the channel bottom. Although this value is
within survey error, it is consistent with previous assessments of sediment
accumulation.
Cross-section B is directly adjacent to the east flood shoal and shows similar
trends of scour along the west bank and infilling within the channel, although
depths along the areas of scour are not as great. Bank encroachment along the
east wall of the navigation channel is more pronounced. Referenced at a depth of
5 ft mlw, sediment deposition added approximately 50 ft to the eastern wall of
the Federal navigation channel over the 10-year period.
Nov 1989
EASTWEST
Mar 1990
May 1980
Aug 1983
Sep 1987
0 50 100 150 200 250
Distance Across Channel, ft
Mattituck Inlet Navigation Channel Cross-Section
May 1980 through March 1990
-20.0
-15.0
-10.0
-5.0
0.0
5.0
El
e
v
a
t
i
o
n
,
f
t
M
L
W
Jun 1985
Figure 4-39a. Mattituck Inlet channel cross-section A
166 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Nov 1989
EASTWEST
Aug 1983
May 1980
Mar 1990
0 50 100 150 200 250
Distance Across Channel, ft
-15.0
-10.0
-5.0
0.0
5.0
El
e
v
a
t
i
o
n
,
f
t
M
L
W
Mattituck Inlet Navigation Channel Cross-Section
May 1980 through March 1990
Figure 4-39b. Mattituck Inlet channel cross-section B
Cross-section C (Figure 4-39c) provides information on the present
morphology of Mattituck Inlet and is close in location to cross-section A. For
comparison to previous figures, the cross section from May 1990 has been
included. The cross section of May 1990 is from a pre-dredging survey, and the
cross section of October 1990 is from a post-dredging survey. Cross-section C
tracks changes in channel width from May 1990 to 2 June 2002. Referenced to a
depth of 5 ft mlw, the east bank appears to have grown only 6-7 ft in thickness
from October 1990 to 20 June 2001. The 2002 survey at this location shows no
indication of growth. Because the other cross sections indicate a trend of bank
encroachment, this cross section was not included in the calculation. The 2 June
2002 cross section does, however, indicate encroachment below this reference
that generally agrees with the bank encroachment indicated in the other cross
sections.
A large of amount of shoaling can be seen along the west bank on cross-
section C, and this portion of the shoal was not dredged in October 1990. This
portion of the flood shoal was presumably allowed to grow because it was not
located within the navigation channel. The eastern edge of the navigation
channel starts at approximately 40 ft into the cross sections shown. The shoaling
indicated did not begin to encroach upon the navigation channel until the mid-
1990s. These cross sections indicate that the east wall of the channel encroached
approximately 10 ft between March 1999 and 2002.
Chapter 4 Morphology Change, and Channel Shoaling and Migration 167
EASTWEST
1999
2001
2002
0 50 100 150 200 250
Distance Across Channel, ft
Mattituck Inlet Navigation Channel Cross-Section
October 1990 through 2002
-20.0
-15.0
-10.0
-5.0
0.0
5.0
El
e
v
a
t
i
o
n
,
f
t
M
L
W
Oct 1990
May 1990
Figure 4-39c. Mattituck Inlet channel cross-section C
Observations during site visits indicate that boat wake action may be a
significant mechanism for the redistribution of sediment within the inlet in the
areas of shoaling. Figures 4-40a and 4-40b show a boat of medium size entering
Mattituck Inlet and the resulting wake arriving obliquely on the area of shoaling
located at the base of the east jetty. The obliquely incident waves can transport
sediment alongshore.
Figure 4-40a. Boat approaching turn at base of jetties, Mattituck Inlet, 9 July
2004, view looking northwest
168 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-40b. Boat wake obliquely incident on area of flood shoal at base of east
jetty, Mattituck Inlet, 9 July 2004
Goldsmith Inlet
To analyze morphology change for the offshore at Goldsmith Inlet, beach
profiles from the 6-8 October 2002 survey are compared to those from a March
1998 survey (OCTI 1998), spanning a 4-1/2 year interval. Analysis of the
migration of the inlet entrance and the inlet channel, growth of the fillet at the
jetty, growth of an attached west bank fillet, and the flood shoal is conducted by
reference to aerial photography.
Offshore morphology change
Figures 4-41a to 4-41k plot comparisons of 1998 (OCTI 1998) and 2002
beach profiles for the areas offshore of Goldsmith Inlet. In some instances,
profile transects were referenced to previously established monuments (OCTI
1998). East of Goldsmith Inlet, the profiles often did not overlap. The profile
surveys indicate a shoreline near equilibrium from 1998 to 2002.
Chapter 4 Morphology Change, and Channel Shoaling and Migration 169
2002
1998
-100 400 900 1400 1900 2400 2900 3400
Distance Across Shore, ft
-25
-20
-15
-10
-5
0
5
10
15
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
20 Goldsmith Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line W 1 (Approx. 600 ft
West of Jetty)
Figure 4-41a. Beach profile W1, west of Goldsmith Inlet, March 1998 and
6-8 October 2002
2002
1998
-100 400 900 1400 1900 2400 2900 3400
Distance Across Shore, ft
-25
-20
-15
-10
-5
0
5
10
15
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
20 Goldsmith Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line W 2 (Approx. 1,200 ft
West of Jetty)
Figure 4-41b. Beach profile W2, west of Goldsmith Inlet, March 1998 and
6-8 October 2002
170 Chapter 4 Morphology Change, and Channel Shoaling and Migration
2002
1998
-100 400 900 1400 1900 2400 2900 3400
Distance Across Shore, ft
-25
-20
-15
-10
-5
0
5
10
15
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
20 Goldsmith Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line W 4 (Approx. 2,300 ft
West of Jetty)
Figure 4-41c. Beach profile W4, west of Goldsmith Inlet, March 1998 and
6-8 October 2002
2002
1998
-100 400 900 1400 1900 2400 2900 3400
Distance Across Shore, ft
-25
-20
-15
-10
-5
0
5
10
15
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
20 Goldsmith Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line E 1 (Approx. 400 ft
East of Inlet)
Figure 4-41d. Beach profile E1, east of Goldsmith Inlet, March 1998 and
6-8 October 2002
Chapter 4 Morphology Change, and Channel Shoaling and Migration 171
1998
2002
-100 400 900 1400 1900 2400 2900 3400
Distance Across Shore, ft
-25
-20
-15
-10
-5
0
5
10
15
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
20 Goldsmith Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line E 2 (Approx. 900 ft
East of Inlet)
Figure 4-41e. Beach profile E2, east of Goldsmith Inlet, March 1998 and
6-8 October 2002
1998
2002
-100 400 900 1400 1900 2400 2900 3400
Distance Across Shore, ft
-25
-20
-15
-10
-5
0
5
10
15
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
20 Goldsmith Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line E 3 (Approx. 1,400 ft
East of Inlet)
Figure 4-41f. Beach profile E3, east of Goldsmith Inlet, March 1998 and
6-8 October 2002
172 Chapter 4 Morphology Change, and Channel Shoaling and Migration
1998
2002
-100 400 900 1400 1900 2400 2900 3400
Distance Across Shore, ft
-25
-20
-15
-10
-5
0
5
10
15
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
20 Goldsmith Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line E 4 (Approx. 1,900 ft
East of Inlet)
Figure 4-41g. Beach profile E4, east of Goldsmith Inlet, March 1998 and
6-8 October 2002
1998
2002
-100 400 900 1400 1900 2400 2900 3400
Distance Across Shore, ft
-25
-20
-15
-10
-5
0
5
10
15
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
20 Goldsmith Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line E 5 (Approx. 2,400 ft
East of Inlet)
Figure 4-41h. Beach profile E5, east of Goldsmith Inlet, March 1998 and
6-8 October 2002
Chapter 4 Morphology Change, and Channel Shoaling and Migration 173
1998
2002
-100 400 900 1400 1900 2400 2900 3400
Distance Across Shore, ft
-25
-20
-15
-10
-5
0
5
10
15
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
20 Goldsmith Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line E 6 (Approx. 2,900 ft
East of Inlet)
Figure 4-41i. Beach profile E6, east of Goldsmith Inlet, March 1998 and
6-8 October 2002
1998
2002
-100 400 900 1400 1900 2400 2900 3400
Distance Across Shore, ft
-25
-20
-15
-10
-5
0
5
10
15
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
20 Goldsmith Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line E 7 (Approx. 3,400 ft
East of Inlet)
Figure 4-41j. Beach profile E7, east of Goldsmith Inlet, March 1998 and
6-8 October 2002
174 Chapter 4 Morphology Change, and Channel Shoaling and Migration
1998
2002
-100 400 900 1400 1900 2400 2900 3400
Distance Across Shore, ft
-25
-20
-15
-10
-5
0
5
10
15
El
e
v
a
t
i
o
n
,
f
t
N
A
V
D
8
8
20 Goldsmith Profile Comparison
Mar 1998 and 6-8 Oct 2002
Line E 8 (Approx. 3,900 ft
East of Inlet)
Figure 4-41k. Beach profile E8, east of Goldsmith Inlet, March 1998 and
6-8 October 2002
Channel migration
Because Goldsmith Inlet is free to migrate to the east and away from the
jetty, the location of its entrance channel is dynamic. The orientation of the
channel, sediment impoundment west of the jetty, and formation of a fillet east of
the jetty are analyzed for times available from aerial photographs. The
reorientation indicates that Goldsmith Inlet is presently an ephemeral inlet, in
contrast to the preceding century when it was apparently more stable and open
(Chapter 2).
Goldsmith Inlet in 1938 and 1955, prior to the 1964 construction of the jetty,
is shown in Figures 4-42a and 4-42b. A small promontory or cusp directly to the
west of the inlet mouth is observed in Figure 4-42b. The promontory may be
associated with blockage by a geological hard point from the glacial moraine.
Alternatively, this feature may be a small relict groin. A hard point would
promote and preserve the stability of Goldsmith Inlet and Goldsmith Pond. The
Goldsmith Inlet channel in its natural state had a width of approximately 10 ft for
the first 450 ft, and widened to an average of approximately 120 ft for the
remainder of the channel issuing into Goldsmith Pond. Sediment grain size
analysis shows the median grain size for the first 500 ft to range from -4 to
-6 φ (16-64 mm). The median grain size of the channel beyond this point ranges
from -1 to -3 φ (2-8 mm).
Figures 4-42c though 4-42l document the location and width of the inlet
entrance of Goldsmith Inlet from 1964 to the present. The relation among
sediment impoundment (1964-1976), the formation of an accretion spit directly
east of the jetty (1976-present), and the eastward migration of the channel
entrance are discussed in the following paragraphs (1976-present).
Chapter 4 Morphology Change, and Channel Shoaling and Migration 175
Figure 4-42a. Goldsmith Inlet channel entrance, 1938 (exact month
and day unknown)
Figure 4-42b. Goldsmith Inlet channel entrance, 11 May 1955
176 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-42c. Goldsmith Inlet channel entrance, 1 April 1964
Figure 4-42d. Goldsmith Inlet channel entrance, 5 October 1966
Chapter 4 Morphology Change, and Channel Shoaling and Migration 177
Figure 4-42e. Goldsmith Inlet channel entrance, 28 April 1969
Figure 4-42f. Goldsmith Inlet channel entrance, 6 April 1976
178 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-42g. Goldsmith Inlet channel entrance, 24 May 1980
Figure 4-42h. Goldsmith Inlet channel entrance, 5 April 1993
Chapter 4 Morphology Change, and Channel Shoaling and Migration 179
Figure 4-42i. Goldsmith Inlet channel entrance, 21 April 1996
Figure 4-42j. Goldsmith Inlet channel entrance, 26-30 April 2001
180 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-42k. Goldsmith Inlet channel entrance, 16 April 2003
Figure 4-42l. Goldsmith Inlet, 15 April 2004
Chapter 4 Morphology Change, and Channel Shoaling and Migration 181
Channel orientation at Goldsmith Inlet in 1938 and 1955, prior to the
construction of the jetty, is illustrated in Figure 4-43a. Channel orientation and
shoreline extent directly east and west of Goldsmith Inlet from 1955 to 1966 are
illustrated in Figure 4-43b, referenced to the location of the jetty. Morphology
change at the entrance of Goldsmith Inlet for this period is characterized by the
introduction of the jetty, the relocation of the inlet entrance, and resulting
impoundment of sediment west of the jetty and shoreline recession east of the
jetty.
Figure 4-43c illustrates channel orientation and shoreline extent directly east
and west of Goldsmith Inlet from 1969 to 1980. The impoundment capacity of
the jetty at Goldsmith Inlet is rapidly being approached in 1969, and the jetty
reached near-field capacity by 1976. Formation of the present-day spit directly
east of the jetty at Goldsmith Inlet had begun by 1976. The inlet experienced
closure at least once in the photographic record (March 1980) and appeared to be
approaching closure in April 1976.
Figure 4-43a. Goldsmith Inlet channel entrance, 1938 and 11 May 1955
182 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-43b. Goldsmith Inlet channel entrance, 11 May 1955,
1 April 1964, and 5 October 1966
Figure 4-43c. Goldsmith Inlet channel entrance, 28 April 1969,
28 April 1976, and 24 May 1980
Chapter 4 Morphology Change, and Channel Shoaling and Migration 183
According to Greenman-Pedersen Associates, P.C. (1981), the Goldsmith
Inlet jetty reached impoundment capacity in 1972 and had become an effective
sediment bypasser. Their analysis, however, indicates that the greatest rates of
erosion on the downdrift beach occurred between 1972-1978. The report
concludes that there is no apparent reason for this acceleration. Analysis in the
present study indicates that an effective sediment bypassing system was not
established until the jetty-attached spit directly east of the jetty had reached a
certain volume and areal extent. The impoundment fillet directly west of the
jetty was the apparent primary sediment sink in this area prior to 1972. After
this, the formation of the spit adjacent to the east side of the jetty became the
primary sediment sink for the local sand-sharing system. This period may have
also been characterized by greater rates of sediment intrusion within the inlet.
Goldsmith Inlet was dredged in 1977 and again in July 1980. Figure 4-42g
shows Goldsmith Inlet was closed on 24 May 1980. This dredging reopened the
inlet. The inlet also appears to have been approaching closure in 1976, and the
dredging of 1977 is assumed to have prevented closure or reopened the inlet soon
after closure. Aerial photographs for the period 1981–1993 were not found.
Records indicate, however, that the Town of Southold regularly dredged the inlet
during this time (Table 2-9). Based on comparison of areal extent of the spit
directly east of the jetty in 1976 and 1993, it is assumed that these dredgings
served to keep the inlet open and the location at the entrance of the inlet
relatively stable.
The present, dynamic morphology of the Goldsmith Inlet channel is apparent
in Figures 4-43d and 4-43e. No dredging records are available for Goldsmith
Inlet after 1990. Fields et al. (1999) estimates that 5,000 cu yd of sediment had
been dredged annually from Goldsmith Inlet. The Southold Town Engineer,
however, has indicated that all dredging operations ceased sometime in the mid-
1990s.1 Ceasing of dredging is apparently reflected in the growth of the spit
directly west of the jetty between 1993 and 1996 (Figure 4-43d).
Channel orientation for 2002-2004 is illustrated in Figure 4-43e. There
appears to have been little migration of the channel entrance between 1996 and
2002, although locational stability may have owed to dredging for which
accurate records are not available. The observed rapid migration and spit
formation of recent times is discussed in the following paragraphs.
1 Personal communication, 22 March 2003, Mr. James. A Richter, Office of the Engineer, Southold
Town Hall, 53095 Main Road, Southold, NY.
184 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-43d. Goldsmith Inlet channel entrance , 5 April 1993 and 21 April 1996
Figure 4-43e. Goldsmith Inlet channel entrance, 16 April 2002,
16 April 2003, and 15 April 2004
Chapter 4 Morphology Change, and Channel Shoaling and Migration 185
Figures 4-44a and 4-44b summarize orientations of the inlet entrance from
1993 to 2004. The aerial photograph of 16 April 2002 approximates the location
and orientation of the channel at the time of the bathymetry survey of 6-8
October 2002. Change in location and morphology of the Goldsmith Inlet
channel entrance between 6-8 October 2002 and 16 April 2003 is substantial.
Sediment accumulation extended the beach 60-80 ft for the 500 ft directly east of
the jetty, and the entrance channel mouth migrated 350 ft to the east. The
effective greater length of the channel diminished the flushing capability of the
inlet and contributed to closure. The acute angle of the inlet relative to the
shoreline, in contrast, allows for more effective sediment bypassing. An
emergency dredging at Goldsmith Inlet took place on 22-26 March 2004, and the
inlet entrance and channel were repositioned.
5 April 1993 21 April 1996
16 April 2002
16 April 2003
Figure 4-44a. Goldsmith Inlet channel entrance orientation, 1993-2003
186 Chapter 4 Morphology Change, and Channel Shoaling and Migration
16 April 2002 15 April 2004
16 April 2003
Figure 4-44b. Goldsmith Inlet channel entrance orientation, 2002-2004
Areal changes of the spit directly east of the jetty are illustrated in
Figure 4-45. Bypassing along the east side of the jetty resulted in 12,000 sq ft
of accreted sediment in 1996 and 17,000 sq ft in 2002. The elevation of the
Goldsmith Inlet jetty is 7 ft NAVD88. Because this spit for the most part
covered the landward portion of the jetty, the thickness of the shoal at both times
is estimated to be 6 ft above the NAVD88 datum. Volume of the spit is
estimated to be 2,700 cu yd in 1996 and 3,800 cu yd in 2002. The average rate
of sediment accumulation along the east side the jetty from 1996 to 2002 is
estimated to be 140 cu yd/year.
The area of the spit along the east side of the jetty increased from
17,000 sq ft on 16 April 2002 to 68,000 sq ft on 16 April 2003. The volume of
sediment located between the jetty and entrance channel is estimated to be 9,000-
12,000-cu yd, with 5,200 to 8,200 cu yd accumulating in a 6-month period. The
areal extent of the spit after the emergency dredging of 22-26 March 2004 is
estimated to be 35,000 sq ft.
Chapter 4 Morphology Change, and Channel Shoaling and Migration 187
5 April 1993
21 April 1996
16 April 2002
16 April 2003
15 April 2004
Figure 4-45. Shoaling east of Goldsmith Inlet jetty, 1993-2004
Channel and flood shoal morphology change
This section begins with a review of the natural morphology of the channel at
Goldsmith Inlet and modifications identified or interpreted to have been
introduced by channel dredging. Evolution and morphology change of the flood
shoal at Goldsmith Inlet in response to these modifications is then analyzed.
The morphology of the channel at Goldsmith Inlet prior to jetty construction
(1938 and 11 May 1955) is shown in Figures 4-46a and 4-46b. Figure 4-46c
shows the morphology of the channel soon after the construction of the jetty
(1 April 1964). The exact date of initial dredging of Goldsmith Inlet in
association with jetty construction is not known. It is apparent from the aerial
photographs that the new-work dredging had taken place by 1 April 1964.
In its natural condition (prior to jetty construction), Goldsmith Inlet had a
well-developed partially dry flood shoal within an area that is now part of the
present-day channel. The northern 450-ft section of the channel was narrow, and
it widened considerably beyond this point, where the natural flood shoal begins.
The original modified channel was dredged along the western bank of the inlet,
while the eastern natural channel was left unmodified. As seen in Figures 4-46c,
a considerable dry portion of the natural flood shoal was left intact as well. The
volume of shoaling at the location of the present-day flood shoal was minimal. It
is believed that material from the initial dredging was placed on the beach
directly east of the inlet.
188 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-46a. Goldsmith Inlet natural flood shoal, 1938 (exact month
and day unknown)
Figure 4-46b. Goldsmith Inlet natural flood shoal, 11 May 1955
Chapter 4 Morphology Change, and Channel Shoaling and Migration 189
Figure 4-46c. Goldsmith Inlet channel with partially intact in-channel
flood shoal, 1 April 1964
The morphology of the in-channel flood shoal, apparent morphology changes
along the east bank, and the evolution of the west bank attached shoal, from 1969
to the present are illustrated and analyzed in Figures 4-46d through 4-46k.
Because the aerial photographs are not tide corrected, and the wet-dry line along
the banks of Goldsmith Inlet is blurred, particularly in areas bounded by
wetlands, these figures should be regarded as approximations. The figures do,
however, present clear trends in morphology change for the features considered.
190 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-46d. Goldsmith Inlet channel with partially intact in-channel
flood shoal, 5 October 1966
Figure 4-46e. Goldsmith Inlet channel, 28 April 1969
Chapter 4 Morphology Change, and Channel Shoaling and Migration 191
Figure 4-46f. Goldsmith Inlet channel, 6 April 1976
Figure 4-46g. Goldsmith Inlet channel, 24 May 1980
192 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-46h. Goldsmith Inlet channel, 5 April 1993
Figure 4-46i. Goldsmith Inlet channel, 21 April 1996
Chapter 4 Morphology Change, and Channel Shoaling and Migration 193
Figure 4-46j. Goldsmith Inlet channel, 16 April 2003
Figure 4-46k. Goldsmith Inlet channel, 15 April 2004
194 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figures 4-47a through 4-47e plot morphology change within the midchannel
area, migration of the intact portion of the natural in-channel flood shoal, and
eventual closure of the eastern, natural channel. The fact that a dry portion of the
natural flood shoal was left intact may have greatly influenced evolution of the
channel and the present-day flood shoal at Goldsmith Inlet. The continued
existence of the dry portion of the natural flood shoal created two channels that
begin 450 ft into the inlet (Figures 4-47a and 4-47b). The western, modified
channel, as well as the initial 450 ft, would be considerably deeper than the
eastern natural channel. During flood tide, gravel and coarse sediment would,
therefore, tend to accumulate within the modified channel.
The sediment that constituted the portion of the natural flood shoal that was
left intact appears to have been redistributed by tidal currents during the time
period considered. Intrusion of new sediment resulted in the eventual closure of
the eastern natural channel and the apparent creation of new wetland along the
east bank (Figures 4-47c through 4-47e).
An attached shoal developed along the west bank and is illustrated in
Figures 4-47c and 4-47e. The evolution of this attached shoal resulted in an
increasingly sigmoidal channel morphology, which modifies the ebb and flood
current (and resulting sediment deposition). Initial growth of this attached shoal
could be discerned in 1976, and no growth was apparent in 1980 and 1993
(Figures 4-47c and 4-47d). The apparent absence of this attached shoal may be
attributable to the aerial photographs for this period being taken at a time of
higher water. It is also possible, however, that this attached shoal had been
dredged. This attached shoal is observed to have grown rapidly in recent years,
indicating increased sediment deposition within the channel (Figure 4-47e).
The location and areal morphology of the flood shoal for the time period
considered is illustrated in Figures 4-48a through 4-48d, referenced against the
present shoreline (15 April 2004). The photographs of 28 April 1969 and
24 May 1980 appear to have been taken at higher water, when only small
portions of the submerged flood shoal were discernible, and are not shown.
Because the extent of the flood shoal that is visible depends on several factors,
particularly water level, values obtained are approximations. They do, however,
indicate trends of movement and growth of the flood shoal at Goldsmith Inlet.
New work modifications introduced to Goldsmith Inlet resulted in the
migration of the natural flood shoal along the east bank. The sediment that
composed this feature apparently relocated to the eastern bank, where the inlet
empties into Goldsmith Pond. This sediment apparently began the formation of
the eastern lobe of the present-day flood shoal (Figures 4-48a and 4-48b).
Chapter 4 Morphology Change, and Channel Shoaling and Migration 195
Figure 4-47a. Goldsmith Inlet channel center, 11 May 1955 and 1 April 1964
Figure 4-47b. Goldsmith Inlet channel center, 5 October 1966 and 28 April 1969
196 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-47c. Goldsmith Inlet channel center, 6 April 1976 and 24 May 1980
Figure 4-47d. Goldsmith Inlet channel center, 5 April 1993 and 21 April 1996
Chapter 4 Morphology Change, and Channel Shoaling and Migration 197
Figure 4-47e. Goldsmith Inlet channel center, 16 April 2003 and 15 April 2004
New shoaling along the west bank and the beginnings of the west lobe of the
present-day flood shoal can be seen in Figure 4-48b, the apparent result of the
deeper channel dredged along the west side of the inlet.
Figure 4-48c outlines the approximate extent of the flood shoal on 5 April
1993 and 21 April 1996. The flood shoal appeared to be reaching maturity at this
point, where its morphology closely resembled its present manifestation. The
eastern and western lobes appeared to be mature and well developed by 1993.
Limiting depth at this location is a prominent control on the present
hydrodynamics of Goldsmith Inlet. The period of flood shoal development
appears to have been followed by a period of channel infilling, where a new lobe
of the flood shoal developed, as seen in the morphology of 21 April 1996.
The areal extent of shoaling within the channel can be seen in Figure 4-48c
for 21 April 1996 and in Figure 4-48d for 16 April 2003 and 15 April 2004. The
well-developed flood shoal probably began blocking the transport of sediment
into Goldsmith Pond, resulting in a new period that is characterized by deposition
within the inlet channel. This observation is supported by the sediment grain
sizes found at this location (Chapter 3). The southern portion of the inlet is
characterized by course to medium sand that is distinct from the larger sediment
found north of this location and the finer sediment that comprises the flood shoal
proper. This period is also characterized by the formation of the attached west-
bank shoal, further supporting the conclusion of flood shoal stability. The
observed in-channel shoal resembles the natural flood shoal of 1955 in many
respects.
198 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figure 4-48a. Goldsmith Inlet flood shoal, 11 May 1955 and 1 April 1964
Figure 4-48b. Goldsmith Inlet flood shoal, 5 October 1966 and 6 April 1976
Chapter 4 Morphology Change, and Channel Shoaling and Migration 199
Figure 4-48c. Goldsmith Inlet flood shoal, 5 April 1993 and 21 April 1996
Figure 4-48d. Goldsmith Inlet flood shoal, 16 April 2003 and 21 April 2004
200 Chapter 4 Morphology Change, and Channel Shoaling and Migration
Figures 4-49 and 4-50 show the east bank of Goldsmith Inlet on 8 October
2002 during rising spring tide. Presently, the east bank of the inlet appears to be
experiencing erosion. Erosion of the wetland perimeter is evident in Figure 4-49,
and a protective bank of fine-grained sediment is seen in Figure 4-50. Figure 4-
51 shows the east bank on 20 February 2004 at high tide. The wetlands are
inundated, and the protective bank of sediment shows erosion and undercutting.
The observed inundation may be related to increased elevation associated with
channel infilling that began in the mid-1990s.
Summary of morphology change at Goldsmith Inlet
Modifications introduced to Goldsmith Inlet have produced a dynamic
morphological response throughout the inlet. The response can be characterized
by development of new features and distinct periods of sedimentation patterns.
Table 4-6 summarizes the major aspects of interpreted morphology change from
1955 to the present and synopsizes discussion of change at the inlet entrance,
within the channel, and at the location of the present-day flood shoal (inlet exit).
In summary, the west accretion fillet reached the seaward tip of the jetty prior
to 6 April 1976 (Figure 4-42f), (by 1972, according to Greenman-Pederson
(1981)), and it is assumed that sediment accretion rates along the east side of the
jetty and within Goldsmith Inlet increased around this time. Construction of the
jetty apparently stabilized the inlet for 17 years by blocking eastward-moving
material, because the first dredging of record occurred in 1977. Subsequently,
Goldsmith Inlet was dredged seven times until 1990, and several times in the
early 1990s. Local sources have indicated that the inlet has not been dredged in
recent years. The inlet apparently maintained a degree of stability from the mid-
1990s to 2002.
Figure 4-49. Goldsmith Inlet, east bank wetlands, during current measurement,
8 October 2002
Chapter 4 Morphology Change, and Channel Shoaling and Migration 201
Figure 4-50. Goldsmith Inlet, east bank wetlands, with protective sand bank,
8 October 2002
Figure 4-51. Goldsmith Inlet, east bank wetland, 20 February 2004
202 Chapter 4 Morphology Change, and Channel Shoaling and Migration
The relatively large tidal range and large sediment grain size contribute to
maintenance of inlet stability. Continual degradation of the jetty at Goldsmith
Inlet, which allows sediment to enter the inlet, acts to reduce inlet stability.
Channel migration between 1996 and 2002 is not known. It is inferred that
increasing rates of sediment bypassing around the jetty and close to shore, owing
to full impoundment on the west side and spit growth on the east side, promote
eastward migration of the inlet entrance. Migration of the channel creates an
increasingly sigmoidal or “S”-shaped configuration, which decreases the flushing
capacity of the inlet because of increasing length of channel and associated
increase in friction.
Table 4-6
Summary of Morphology Change at Goldsmith Inlet, 1955 to
Present
Date Inlet entrance Inlet channel Inlet Exit
1955 -- Natural in-channel flood shoal --
1963 - 1964 Construction of jetty --
1964 New work dredging New work dredging New work dredging
1964 - 1972
Impoundment west
of jetty and
associated erosion
east of jetty
Natural flood shoal migration
Initial formation of present
east and west lobes
1972 - 1976
Initial formation of
spit east of jetty
Assumed
acceleration of
sediment intrusion
-- Mature and stable east lobe
1976 - 1980 Closure of Inlet
(1980)
Closure of eastern natural
channel
Continued flood shoal
growth
1980 - 1990
Assumed stability
through regular
dredging
Establishment of
natural effective
sediment bypassing
--
Mature and stable west
lobe
Period of channel infilling
begins
1990 - 2002
Continued spit
development
Initial channel
migration
Development of attached west
bank shoal
Channel infilling in mid -
channel
Continued period of
channel infilling
2002 - 2003
Rapid spit formation
Rapid eastward
channel migration
Inundation of Wetlands –
presumably from raised
elevation of channel infilling
Continued period of
channel infilling
April 2004 Dredging and
reorientation of inlet -- --
Chapter 4 Morphology Change, and Channel Shoaling and Migration 203
Although a larger channel will increase friction presented to the flow within
it, it can be inferred that alignment of the channel almost parallel to shore makes
the inlet an efficient bypasser during ebb flow. At that stage of tide, an ebb
current of any strength would reinforce wave action and the wave-induced
longshore current directed to the east to transport material down the coast.
Therefore, it may be feasible to maintain the inlet with less dredging by allowing
the channel to remain oriented toward the east than it is to dredge and realign the
channel straight out toward the sound. Likewise, the orientation toward the east
makes it difficult for sediment streaming off of the spit on the east side of the
jetty to turn almost 180 deg and enter the inlet entrance.
Finally, development and maturation of the existing flood shoal has served to
block sediment transport into Goldsmith Pond, resulting in sediment deposition
within the channel since 1993. The limiting depth that has resulted from the
development of this feature has also served to accentuate asymmetries in flood
and ebb current velocity (discussed in Chapter 5). At present, given the rapid
eastward migration of the inlet entrance and the apparent increases in in-channel
sedimentation rates, Goldsmith Inlet can be said to be an autonomic system,
where changes within it promote a positive feedback cycle, thereby increasing
the observed rates of change. Maintenance of the inlet mouth in an eastward
orientation may only require minor dredging, thereby reinforcing the autonomous
behavior. An eastward orientation would maximize sediment bypassing while
allowing a minimal amount of sediment to enter the inlet channel.
204 Chapter 5 Circulation Analysis
5 Circulation Analysis
This chapter describes calculations of circulation and water level at Mattituck
Inlet and Goldsmith Inlet performed to infer and interpret sediment-transport
pathways associated with tidal flow. Field measurements (Chapter 4) made in
October 2002 of bathymetry, water level, and current provided data for driving
and validating the models.
For Mattituck Inlet, tidal hydrodynamics (water level and current) were
simulated with the ADvanced CIRCulation (ADCIRC) model (Luettich et al.
1992), a two-dimensional (2-D) finite-element hydrodynamic model that
calculates the depth-averaged horizontal circulation. For Goldsmith Inlet, tidal
hydrodynamics were modeled with DYNLET (DYNamic Implicit Model of One-
Dimensional Tidal Flow Through InLETs) (Amein and Kraus 1991), which is a
one-dimensional (1-D) finite-difference model suited to narrow inlets and areas
with minimal cross-channel and cross-bay circulation.
Mattituck Inlet
Water-surface elevation and current velocity for the Long Island Sound,
Mattituck Inlet, and Mattituck Creek were calculated with ADCIRC. A regional
ADCIRC grid of the New York Bight and the Long Island Sound (Figure 5-1)
developed in the Coastal Inlets Research Program (Militello et al. 2000) was
modified by increasing resolution at the study site and incorporating data from
the October 2002 bathymetry survey at Mattituck Inlet. The model was then
validated against regional and local measurements.
The finite-element ADCIRC grid allows fine resolution to be specified in
areas of interest. The model domain for this study incorporated horizontal grid
elements with lengths ranging from 2.8 km along the Atlantic Ocean southeastern
model domain boundary to less than 10 m within Mattituck Creek. The model
grid consisted of 15,113 nodes and 27,851 elements. The ADCIRC grid for the
study area is shown in Figure 5-2, and the grid for Mattituck Inlet and Mattituck
Creek is shown in Figure 5-3. The regional grid assures input of reliable forcing
to accurately reproduce tidal phasing and amplitude.
Chapter 5 Circulation Analysis 205
Figure 5-1. Regional ADCIRC grid – New York Bight and Long Island Sound
(after Militello et al. 2000)
Figure 5-2. Mattituck Inlet and Mattituck Creek, ADCIRC model bathymetry
206 Chapter 5 Circulation Analysis
Figure 5-3. Close view of Mattituck Inlet, ADCIRC model bathymetry
To explore possible relations between the morphology and circulation (to
infer sediment transport pathways) at Mattituck Inlet, three alternative
morphologies were modeled. The initial ADCIRC grid incorporated the
bathymetry survey of 6-8 October 2002 and represents a pre-dredging condition
at Mattituck Inlet. The second grid (Alternative 1) had the same bathymetry
except that the area at the flood shoal at the base of the east jetty was removed to
represent a post-dredging condition. A third grid (Alternative 2) was developed
to approximate the morphology of Mattituck Inlet circa 1891, before construction
of the jetties and channel deepening by new-work dredging. Alternative 2 was
created to examine the relation between tidal currents at Mattituck Inlet and the
offshore shoal.
Model validation
ADCIRC was run with default value parameters. The bottom friction
coefficient is the main parameter, and its default value is 0.0025. The model
simulated water level and current velocity for the period 18 September 2002 to
18 October 2002, with a time-step of 0.25 sec. This relatively small time-step
was necessary because of fine resolution required to represent the navigation
channel and Mattituck Creek.
Regional validation. Predictions of the model were verified regionally by
comparing calculations to published NOS water-level records of selected stations
within Long Island Sound, with local water-elevation measurements at Mattituck
Inlet and Mattituck Creek collected from 19 September to 8 October 2002, and
with current velocity measurements within Mattituck Creek collected
7-8 October 2002. The three locations within Long Island Sound (Figure 5-4) are
Chapter 5 Circulation Analysis 207
Eaton’s Neck in Huntington Harbor, Huntington, Long Island, NY (40º57.2’N,
73º24’W); New Haven Harbor, New Haven, CT (41º17.0’N, 72º54.5’W); and
Kings Point, NY (40º48.6’N, 73º45.9’W).
Figures 5-5a, 5-5c, and 5-5e show comparisons for the period of field data
collection (18 September – 8 October 2002), and Figures 5-5b, 5-5d and 5-5f
show comparisons for 5-8 October 2002, a period of spring tide. The water-level
plots for these locations validate the model output for the southern boundary of
the Long Island Sound (the north shore of Long Island), the northern boundary of
the Long Island Sound (the south shore of Connecticut), and the western portion
of the Long Island Sound, respectively. These plots also illustrate the tidal
signature of the Long Island Sound, where mean tide amplitudes increases from
east to west (Chapter 2). Agreement with both tidal phase and amplitude is seen.
Occasional deviation is observed between calculation and measurements,
attributed primarily to neglect of wind forcing in the model for the present
application. At Kings Point, under predictions of ADCIRC are believed to be
related to the coarseness of the grid in the area of the NOS station. Increased
resolution of the grid supplemented with recent and denser bathymetry
measurements would improve agreement.
Figure 5-4. NOS stations and 19 September - 8 October 2002 survey tide gauge
locations
208 Chapter 5 Circulation Analysis
NOS Measurements
ADCIRC Calculations
September 2002 - October 2002 GMT
9/29 9/19 9/24 10/4
Eatons Neck Huntington Harbor
Water Level
-2.0
-1.5
-1.0
-0.5
0.0
Wa
t
e
r
L
e
v
e
l
,
m
N
A
V
D
8
8
0.5
1.0
1.5
2.0
10/9
Figure 5-5a. Water level at Eaton’s Neck, Huntington Harbor; NOS
measurements and ADCIRC calculations, 19 September -
8 October 2002
NOS Measurements
ADCIRC Calculations
10/810/710/610/5
5-7 October 2002 GMT
Eatons Neck Huntington Harbor
Water Level
-2.0
-1.5
-1.0
-0.5
Wa
t
e
r
L
e
v
e
l
,
m
N
A
V
D
8
8
0.0
0.5
1.0
1.5
2.0
Figure 5-5b. Water level at Eaton’s Neck, Huntington Harbor; NOS
measurements and ADCIRC calculations, 5-8 October 2002
Chapter 5 Circulation Analysis 209
NOS Measurements
ADCIRC Calculations
September 2002 - October 2002 GMT
10/9
New Haven Harbor
Water Level
-2.0
-1.5
-1.0
-0.5
Wa
t
e
r
L
e
v
e
l
,
m
N
A
V
D
8
8
0.0
0.5
1.0
1.5
2.0
10/4 9/29 9/249/19
Figure 5-5c. Water level at New Haven Harbor, New Haven; NOS
measurements and ADCIRC calculations, 19 September -
8 October 2002
NOS Measurements
ADCIRC Calculations
10/810/710/6
Eatons Neck Huntington Harbor
Water Level
-2.0
-1.5
-1.0
-0.5
Wa
t
e
r
L
e
v
e
l
,
m
N
A
V
D
8
8
0.0
0.5
1.0
1.5
2.0
10/5
5-7 October 2002 GMT
Figure 5-5d. Water level at New Haven Harbor, New Haven; NOS
measurements and ADCIRC calculations, 5-8 October 2002
210 Chapter 5 Circulation Analysis
NOS Measurements
ADCIRC Calculations
September 2002 - October 2002 GMT
10/910/4 9/29 9/249/19
Kings Point
Water Level
-2.0
-1.5
-1.0
-0.5
Wa
t
e
r
L
e
v
e
l
,
m
N
A
V
D
8
8
0.0
0.5
1.0
1.5
2.0
Figure 5-5e. Water level at Kings Point; NOS measurements and ADCIRC
calculations, 19 September - 8 October 2002
NOS Measurements
ADCIRC Calculations
10/810/7-2.0
-1.5
-1.0
-0.5
Wa
t
e
r
L
e
v
e
l
,
m
N
A
V
D
8
8
0.0
0.5
1.0
1.5
2.0 Kings Point
Water Level
10/610/5
5-7 October 2002 GMT
Figure 5-5f. Water level at Kings Point; NOS measurements and ADCIRC
calculations, 5-8 October 2002
Chapter 5 Circulation Analysis 211
Local validation. ADCIRC calculations of water level were compared to
measurements made at Mattituck Inlet and Mattituck Creek from 19 September
to 8 October 2002 (Figures 5-6a through 5-6d). The locations of the tide gauges
for this survey are given in Figure 3-23. Both amplitude and phase of the
measurements are reproduced. The tidal signal maintains amplitude or increases
in amplitude at the creek station because of the constricted flow there.
Measurements
ADCIRC Calculations
September 2002 - October 2002 GMT
10/9 10/4 9/29
Mattituck Inlet Water Level
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Wa
t
e
r
L
e
v
e
l
,
m
N
A
V
D
8
8
2.0
9/249/19
Figure 5-6a. Water level at Mattituck Inlet, near west jetty; measurements and
ADCIRC calculations, 19 September - 8 October 2002
Measurements
ADCIRC Calculations
10/5 10/6 10/7
Mattituck Inlet Water Level
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Wa
t
e
r
L
e
v
e
l
,
m
N
A
V
D
8
8
2.0
10/8
5-7 October 2002 GMT
Figure 5-6b. Water level at Mattituck Inlet, near west jetty; measurements and
ADCIRC calculations, 5-8 October 2002
212 Chapter 5 Circulation Analysis
Measurements
ADCIRC Calculations
September 2002 - October 2002 GMT
10/9
Mattituck Creek Water Level
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Wa
t
e
r
L
e
v
e
l
,
m
N
A
V
D
8
8
2.0
10/49/299/249/19
Figure 5-6c. Water level at Mattituck Creek; measurements and ADCIRC
calculations, 19 September - 8 October 2002
Measurements
ADCIRC Calculations
10/610/5 10/7 10/8
Mattituck Creek Water Level
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Wa
t
e
r
L
e
v
e
l
,
m
N
A
V
D
8
8
2.0
5-7 October 2002 GMT
Figure 5-6d. Water level at Mattituck Creek; measurements and ADCIRC
calculations, 5-7 October 2002
Chapter 5 Circulation Analysis 213
Figure 5-7 plots current velocity measurements collected 7-8 October 2002
(Current meter 1) and ADCIRC calculations. The model reproduces both the
amplitude and phase of the current. The calculation exhibits a broad or double-
peaked crest and trough in the current. The measurements contain these features,
somewhat obscured by noise in the signal. The deviation from a sine curve is
caused by nonlinearity in the tidal wave as it shoals into shallow water from
Long Island Sound.
________ ADCIRC Calculations
Measurements________Mattituck Creek Current Velocity
-60
-40
-20
0
20
40
Ve
l
o
c
i
t
y
,
c
m
/
s
e
c
60
7.00 7.50 8.00 8.50
7-8 October 2002
9.00
Figure 5-7. Current velocity at Mattituck Creek; measurements and ADCIRC
calculations, 7-8 October 2002
Pre-dredging condition (2002)
Calculated current velocities, based on the bathymetric survey data of
6-8 October 2002, are presented here. Calculated velocities offshore of
Mattituck Inlet range from 0 to 0.6 m/sec, and calculated velocities within
Mattituck Inlet range from 0 to 0.5 m/sec. Near-maximum calculated flood and
ebb current velocities for the offshore study area are shown in Figures 5-8a and
5-8b, respectively. These figures plot the calculated near-maximum flood and
ebb tide velocities during a period of spring tide, at approximately 1200 and 1830
GMT on 7 October 2002, respectively. The velocities are termed near-maximum
in that the time of maximum was sought for the area around the inlet, which may
not be the maximum in the channel or in the nearshore.
214 Chapter 5 Circulation Analysis
Figure 5-8a. Near-maximum flood-tide velocity, Mattituck Inlet offshore area,
1200 GMT, 7 October 2002
Figure 5-8b. Near-maximum ebb-tide velocity, Mattituck Inlet offshore area,
1830 GMT, 7 October 2002
Near-maximum flood and ebb current velocities in the vicinity of the inlet
entrance and the offshore shoal are illustrated in Figures 5-8c and 5-8e.
Figures 5-8d and 5-8f display the same current velocity vectors overlying the
bathymetry for this area. The influence of the jetties at Mattituck Inlet on the
direction of the depth-averaged current can be seen in Figures 5-8g and 5-8h,
where eddies form and current reversals occur.
Chapter 5 Circulation Analysis 215
Figure 5-8c. Near-maximum flood-tide velocity, Mattituck Inlet offshore shoal
area, 1200 GMT, 7 October 2002
Figure 5-8d. Near-maximum flood-tide velocity and depth, Mattituck Inlet
offshore shoal area, 1200 GMT, 7 October 2002
216 Chapter 5 Circulation Analysis
Figure 5-8e. Near-maximum ebb-tide velocity, Mattituck Inlet offshore shoal
area, 1830 GMT, 7 October 2002
Figure 5-8f. Near-maximum ebb-tide velocity and depth, Mattituck Inlet
offshore shoal area, 1830 GMT, 7 October 2002
Chapter 5 Circulation Analysis 217
Figure 5-8g. Flood-current eddies and depth, directly west of Mattituck Inlet,
1200 GMT, 7 October 2002
Figure 5-8h. Ebb-current eddies and depth, directly east of Mattituck Inlet,
1830 GMT, 7 October 2002
218 Chapter 5 Circulation Analysis
A notable result for consideration of sediment transport is that the calculated
current velocity at the inlet entrance has a maximum of only about 0.5 m/sec for
the spring tidal conditions simulated. The maximum current through the entrance
would be less for typical tide and neap tide. It is empirically known that the
annual mean-maximum velocity to maintain a minimum stable inlet channel
cross section is about 1 m/sec for inlets on sandy coasts. Because the coarser
sands and gravel predominant at Mattituck Inlet would require even stronger
current velocity than 1 m/sec to sweep the channel clear, it can be concluded that
the channel cross-sectional area is greater than the minimum (for sandy coasts).
Figures 5-9a and 5-9c display near-maximum flood- and ebb-tide current
velocities within the channel. Figures 5-9b and 5-9d show these current velocity
vectors overlaying the inlet and Federal navigation channel bathymetry. The
greatest velocities occur adjacent to the area of the flood shoal along the east
bank, opposite the area of shoaling, where Mattituck Inlet takes a sharp turn to
the east and the channel becomes constricted. Magnitude of velocity reaches
0.5 m/sec.
Figure 5-9a. Near-maximum flood-tide velocity, Mattituck Inlet, 1200 GMT,
7 October 2002
Chapter 5 Circulation Analysis 219
Figure 5-9b. Near-maximum flood-tide velocity and depth, Mattituck Inlet, 1200
GMT, 7 October 2002
Figure 5-9c. Near-maximum ebb-tide velocity, Mattituck Inlet, 1830 GMT,
7 October 2002
220 Chapter 5 Circulation Analysis
Figure 5-9d. Near-maximum ebb-tide velocity and depth, Mattituck Inlet, 1830
GMT, 7 October 2002
Figures 5-10a and 5-10c display near-maximum flood- and ebb-tide current
velocities within Mattituck Inlet and the northern portion of Mattituck Creek.
Figures 5-10b and 5-10d display these velocity vectors overlying the bathymetry
of these areas. Current magnitude exceeds 0.5 m/sec in the creek in narrow
areas.
Figure 5-10a. Near-maximum flood-tide velocity, Mattituck Inlet flood shoal area,
1200 GMT, 7 October 2002
Chapter 5 Circulation Analysis 221
Figure 5-10b. Near-maximum flood-tide velocity and depth, Mattituck Inlet flood
shoal area, 1200 GMT, 7 October 2002
Figure 5-10c. Near-maximum ebb-tide velocity, Mattituck Inlet flood shoal area,
1830 GMT, 7 October 2002
222 Chapter 5 Circulation Analysis
Figure 5-10d. Near-maximum ebb-tide velocity and depth, Mattituck Inlet flood
shoal area, 1830 GMT, 7 October 2002
Alternative 1: Post-dredging morphology
To examine the control of the main area of shoaling on the current velocity
within and around Mattituck Inlet, an alternative (synthetic) grid with this area of
shoaling removed was developed. The results of this alternative are analyzed
here and compared to the pre-dredging configuration of 2002. The dredged shoal
configuration can be considered as an approximation of the morphology of
Mattituck Inlet after the dredging of 17–24 March 20041. Some differences exist,
however, between the synthetic and actual dredging. The dredging of
17-24 March 2004 removed a significant portion of the shoal located on the west
bank of the inlet, which is not represented in the synthetic grid. Also, the extent
of the flood shoal removed from this grid is probably greater than the actual
amount removed during the dredging of 2004, because sediment is expected to be
removed only within the limits of the Federal navigation channel in actual
dredging.
Figure 5-11a illustrates near-maximum flood current velocity near the flood
shoal for the 2002 ADCIRC grid and Figure 5-11b illustrates maximum flood
current velocity for this area for the dredged (flood) shoal alternative. Near-
maximum ebb current velocity for this area is illustrated in Figure 5-11c (pre-
dredging) and Figure 5-11d (post-dredging). The bathymetry of 6-8 October
2002 and the introduced changes in morphology for this alternative are illustrated
in Figures 5-11e and 5-11f. Dredging of the flood shoal reduces velocity
magnitude in the vicinity of dredging, with changes in velocity elsewhere being
minor.
1 The synthetic post-dredging grid was created and calculations performed before the March 2004
dredging took place.
Chapter 5 Circulation Analysis 223
Figure 5-11a. Near-maximum flood-tide velocity, Mattituck Inlet, pre-dredging
grid
Figure 5-11b. Near-maximum flood-tide velocity, Mattituck Inlet, post-dredging
grid
224 Chapter 5 Circulation Analysis
Figure 5-11c. Near-maximum ebb-tide velocity, Mattituck Inlet, pre-dredging grid
Figure 5-11d. Near-maximum ebb-tide velocity, Mattituck Inlet, post-dredging
grid
Chapter 5 Circulation Analysis 225
Figure 5-11e. Near-maximum flood-tide velocity and depth, Mattituck Inlet pre-
dredging grid
Figure 5-11f. Near-maximum flood-tide velocity and depth, Mattituck Inlet post-
dredging grid
Figure 5-12 focuses on the location of synthetic dredging of the flood shoal,
and current velocity at selected points is plotted in Figures 5-13a through 5-13c.
The dredging of the flood shoal is calculated to reduce current velocity at the area
of strongest flow by approximately 30 percent. The peaks of both ebb and flood
current are reduced.
226 Chapter 5 Circulation Analysis
Figure 5-12. Comparative current velocity plot locations
10/910/510/410/3 10/6 10/810/7
October 2002 GMT
Flood Shoal Area
(Location A)
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
Cu
r
r
e
n
t
v
e
l
o
c
i
t
y
,
m
/
s
e
c
Post-dredging
Pre-dedging
Figure 5-13a. Current velocity directly north of Mattituck Inlet east bank flood
shoal, pre-dredging, and synthetic post-dredging condition
(Location A)
Chapter 5 Circulation Analysis 227
10/910/510/410/3 10/6 10/810/7
Post-dredging
Pre-dedging
October 2002 GMT
Flood Shoal Area
(Location B)
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
Cu
r
r
e
n
t
v
e
l
o
c
i
t
y
,
m
/
s
e
c
Figure 5-13b. Current velocity directly north of Mattituck Inlet east bank flood
shoal, pre-dredging, and synthetic post-dredging condition
(Location B)
10/910/510/410/3 10/6 10/810/7
Post-dredging
Pre-dedgingFlood Shoal Area
(Location C)
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
Cu
r
r
e
n
t
v
e
l
o
c
i
t
y
,
m
/
s
e
c
October 2002 GMT
Figure 5-13c. Current velocity directly north of Mattituck Inlet east bank flood
shoal, pre-dredging, and synthetic post-dredging condition
(Location C)
228 Chapter 5 Circulation Analysis
Alternative 2: Natural morphology with offshore shoal
To examine a possible hydrodynamic, hence sediment-transport, relation
between Mattituck Inlet and the offshore shoal located to the east, an alternative
grid of Mattituck Inlet representative of its natural state was developed. The
results of this alternative are analyzed here and compared to the pre-dredging
configuration of 2002. The morphology representing the natural (pre-jetty) state
is based on that of the inlet in 1891 (Figure 4-10). The east-directed spit shown
in Figure 4-10 was truncated in this grid, because the apparent great spit length
was not considered to be representative of Mattituck Inlet in typical natural
equilibrium. The depth at the center of Mattituck Inlet and Mattituck Creek was
taken to be approximately 1.3-1.5 m NAVD88. This depth was selected because
the spring tide range at Mattituck Inlet is about 2 m, and there is no indication in
the historic record that the inlet and Mattituck Creek became dry.
The tidal prism at Mattituck Inlet is 4.32 × 107 cu ft. Applying the Jarrett
(1976) relation for Atlantic Coast inlets with no jetties (discussed in
Chapter 6),60 . 1 0 75.37 10CAP−=× , the channel cross-sectional area of Mattituck
Inlet in its natural state is estimated to be 794 sq ft. If the width of Mattituck
Inlet in a natural state is taken to be 175 ft, the resulting average depth is 4.5 ft
NAVD88, or 1.38 m. Finally, the historic presence of a tidal mill at Mattituck
Inlet suggests presence of water of at least this depth.
The hydrodynamic behavior of Mattituck Inlet in its assumed (synthetic)
natural state differs considerably from that of Mattituck Inlet in its present
modified state. The current at the natural Mattituck Inlet displays similar
properties to the present Goldsmith Inlet. The natural Mattituck Inlet is found to
be strongly flood-dominant, and the phase lag between the offshore and creek
water-level peaks and troughs is pronounced.
Figures 5-14a through 5-14i display calculated tidal velocities offshore of
and through Mattituck Inlet for various times during a full spring tidal cycle.
Figures 5-14a and 5-14b illustrate Mattituck Inlet at 1200 GMT 7 October 2002,
the time of near-maximum offshore current velocity. This time is equivalent to
that of the near-maximum offshore current velocity illustrated in Figure 5-8a.
For comparison to Figure 5-8a, Figure 5-14a is displayed with the same contour
interval range (0-0.6 m). Figure 5-14b illustrates calculation results for this time
with a contour interval range of 0–3 m, for comparison to subsequent figures.
During this time of near-maximum offshore flood current, the inlet is nearing the
end of ebb tide.
Chapter 5 Circulation Analysis 229
Figure 5-14a. Mattituck Inlet natural state, near-maximum offshore spring flood-
tide velocity, 1200 on 7 October 2002
Figure 5-14b. Mattituck Inlet natural state, near-maximum offshore spring flood-
tide velocity, 1200 on 7 October 2002
Figure 5-14c illustrates calculated current velocities at 1230 GMT on
7 October 2002. The offshore flood current velocities remain near peak, and the
inlet has begun to flood. Current velocities at 1430 GMT on 7 October 2002 are
illustrated in Figure 4-14d. This is the point of maximum flood current velocity
at the mouth of the inlet, while the offshore remains in a flood portion of the tidal
cycle.
230 Chapter 5 Circulation Analysis
Figure 5-14c. Mattituck Inlet natural state, offshore and inlet spring flood-tide
velocity, 1230 on 7 October 2002
Figure 5-14d. Mattituck Inlet natural state, offshore spring flood-tide and near-
maximum inlet spring flood-tide velocity, 1430 on 7 October 2002
Chapter 5 Circulation Analysis 231
Figure 5-14e illustrates calculated current velocity at 1530 GMT on
7 October 2002. An ebb tide has begun offshore, but the inlet continues to flood
at strong velocity relative to the maximum inlet flood current velocities. The
offshore flood current velocity remains near peak, and the inlet has begun to
flood. Current velocities at 1830 GMT on 7 October 2002 are illustrated in
Figure 5-14f. The point of near-maximum ebb current velocity has been reached
offshore, and the inlet is in an ebb stage of the tidal cycle. This figure can be
compared to Figures 5-17 and 5-20, which illustrates results for the same time for
a representative 2002 pre-dredging morphology at Mattituck Inlet.
Figure 5-14e. Mattituck Inlet natural state, offshore spring ebb-tide and inlet
spring flood-tide velocity, 1530 on 7 October 2002
Figure 5-14f. Mattituck Inlet natural state, near maximum offshore spring ebb-
tide and inlet spring ebb-tide velocity, 1830 on 7 October 2002
232 Chapter 5 Circulation Analysis
Figure 5-14g illustrates calculated current velocity at 2100 GMT 7 October
2002. Ebb tide current velocity at the mouth of the inlet approaches 2 m/sec, a
velocity much greater than the typical calculated spring tide maximum of
0.5 m/sec found at the existing inlet. Figure 5-14h illustrates current velocity at
2200, a period when flood tide has begun offshore and the inlet remains in a
stage of ebb tide. Figure 5-14i illustrates current velocity at 0030 on 8 October
2002. The area in is in a tidal stage the same as that of Figure 5-14a, the first
figure in this series.
Figure 5-14g. Mattituck Inlet natural state, offshore spring ebb-tide and inlet near
maximum spring ebb-tide velocity, 2100 on 7 October 2002
Figure 5-14h. Mattituck Inlet natural state, offshore spring flood-tide and inlet
spring ebb-tide velocity, 2200 on 7 October 2002
Chapter 5 Circulation Analysis 233
Figure 5-14i. Mattituck Inlet natural state, near maximum offshore spring flood-
tide and inlet spring ebb-tide velocity, 0030 on 8 October 2002
Figure 5-15 displays locations offshore and within the inlet where water level
and current velocity calculation results were extracted to examine the differences
in hydrodynamic behavior between the offshore area and Mattituck Inlet in its
natural state. Location C is near the present-day flood shoal, and Location D is
near the site of the 19 September - 8 October 2002 water level and current meter
data collection. Figures 5-16a through 5-16c illustrate differences in water-
surface elevations at these locations, and Figures 5-17a through 5-17c compare
current velocities.
Location A
Location B
Location C
Location D
Location A
Location B
Location C
Location D
Figure 5-15. Mattituck Inlet assumed (synthetic) natural state and offshore
water level and current velocity comparison locations
234 Chapter 5 Circulation Analysis
10/910/510/410/3 10/6 10/810/7
October 2002 GMT
Offshore (Location A)
Inlet Mouth (Location B)
-3
-2
-1
0
1
2
3
Wa
t
e
r
L
e
v
e
l
,
m
N
A
V
D
8
8
Mattituck Inlet and Offshore Area
Water Level Comparison
Figure 5-16a. Mattituck Inlet natural state and offshore water level comparison
(Locations A and B)
10/910/5 10/810/7
October 2002 GMT
10/3 10/4 10/6
Offshore (Location A)
Flood shoal area (Location C)
Mattituck Inlet and Offshore Area
Water Level Comparison
-3
-2
-1
0
1
2
3
Wa
t
e
r
L
e
v
e
l
,
m
N
A
V
D
8
8
Figure 5-16b. Mattituck Inlet natural state and offshore water level comparison
(Locations A and C)
Chapter 5 Circulation Analysis 235
10/910/5 10/810/7
October 2002 GMT
10/3 10/4 10/6
Offshore (Location A)
Mattiuck Creek (Location D)
Mattituck Inlet and Offshore Area
Water Level Comparison
-3
-2
-1
0
1
2
3
Wa
t
e
r
L
e
v
e
l
,
m
N
A
V
D
8
8
Figure 5-16c. Mattituck Inlet natural state and offshore water level comparison
(Locations A and D)
10/910/510/410/3 10/6 10/810/7
October 2002 GMT
Inlet Mouth (Location B)
Offshore (Location A)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Cu
r
r
e
n
t
v
e
l
o
c
i
t
y
,
m
/
s
e
c
Mattituck Inlet
and Offshore Area
Figure 5-17a. Mattituck Inlet natural state and offshore current velocity
comparison (Locations A and B)
236 Chapter 5 Circulation Analysis
10/910/5 10/810/710/3 10/4 10/6
Mattituck Inlet
and Offshore Area
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Cu
r
r
e
n
t
v
e
l
o
c
i
t
y
,
m
/
s
e
c
October 2002 GMT
Flood shoal area (Location C)
Offshore (Location A)
Figure 5-17b. Mattituck Inlet natural state and offshore current velocity
comparison (Locations A and C)
10/910/5 10/810/710/3 10/4 10/6
Mattituck Creek (Location D)
Offshore (Location A)
October 2002 GMT
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Cu
r
r
e
n
t
v
e
l
o
c
i
t
y
,
m
/
s
e
c
Mattituck Inlet
and Offshore Area
Figure 5-17c. Mattituck Inlet natural state and offshore current velocity
comparison (Locations A and D)
Chapter 5 Circulation Analysis 237
Offshore shoal. The calculated hydrodynamics at Mattituck Inlet in a
natural state and the offshore shoal located to the east are displayed in
Figures 5-18a through 5-18h. This series of figures illustrates current velocity
and current velocity vectors overlying bathymetry for the spring tide periods of
near-maximum offshore flood current velocity, near-maximum inlet flood current
velocity, near-maximum offshore ebb current velocity, and near-maximum inlet
ebb current velocity, respectively. Figure 5-18a illustrates current velocity at
1200 on 7 October 2002, the time of near-maximum offshore flood current.
Figures 5-18b displays the same current velocity vectors overlying the inlet and
offshore shoal bathymetry.
Figure 5-18a. Near-maximum offshore flood-tide velocity, Mattituck Inlet offshore
shoal area, 1200 GMT on 7 October 2002
238 Chapter 5 Circulation Analysis
Figure 5-18b. Near-maximum offshore flood-tide velocity and depth, Mattituck
Inlet offshore shoal area, 1200 GMT on 7 October 2002
Figure 5-18c illustrates current velocity at 1430 on 7 October 2002, the time
of near-maximum inlet flood current. Figures 5-18d displays the same current
velocity vectors overlying the inlet and offshore shoal bathymetry.
Figure 5-18c. Near-maximum inlet flood-tide velocity, Mattituck Inlet offshore
shoal area, 1430 GMT on 7 October 2002
Chapter 5 Circulation Analysis 239
Figure 5-18d. Near-maximum inlet flood-tide velocity and depth, Mattituck Inlet
offshore shoal area, 1430 GMT on 7 October
Figure 5-18e illustrates current velocity at the model at 1830 7 October 2002,
the time of near-maximum offshore ebb current. Figure 5-18f displays the same
current velocity vectors overlying the inlet and offshore shoal bathymetry.
Figure 5-18e. Near-maximum offshore ebb-tide velocity, Mattituck Inlet offshore
shoal area, 1830 GMT on 7 October 2002
240 Chapter 5 Circulation Analysis
Figure 5-18f. Near-maximum offshore ebb-tide velocity and depth, Mattituck
Inlet offshore shoal area, 1830 GMT on 7 October
Figure 5-18g illustrates current velocity at 2030 on 7 October 2002, the time
of near-maximum inlet ebb current. Figure 5-18h displays these same current
velocity vectors overlying the inlet and offshore shoal bathymetry. When the
current is at its peak of near 1.87 m/sec, current velocity magnitudes diminish
greatly with distance from the inlet entrance. The maximum tidal current
velocity at the western extreme of the offshore shoal is calculated to be
0.36 m/sec. Figure 5-19 illustrates the locations of the current velocities plotted
in Figures 5-20a and 5-20b, which include the offshore bathymetry. Current
velocities shown in Figure 5-20b are nearly equivalent and are, therefore,
difficult to discern.
For a configuration representing Mattituck Inlet in its natural state, prior to
stabilization by jetties, the depth-averaged ebb-tidal current velocity at the
offshore shoal is relatively weak, reaching about 0.35 m/sec for short durations.
Such a current velocity exceeds the threshold of motion for medium sand grains,
and the presence of wave orbital velocities near the bottom would further
mobilize sand and make it available for transport. The direction of the calculated
ebb current at maximum velocity is compatible with formation of an ebb shoal at
the general location of the offshore shoal. However, the highly linear shape of
the offshore shoal does not conform with the horizontal pattern of the ebb
current, which tends to expand in areas beyond the location of the offshore shoal.
Also, the relatively short duration when sand could be transported further
indicates that the offshore shoal is not a relict ebb shoal of the historic Matttituck
Inlet.
Chapter 5 Circulation Analysis 241
Figure 5-18g. Near-maximum inlet ebb-tide velocity, Mattituck Inlet offshore
shoal area, 2030 GMT on 7 October 2002
Figure 5-18h. Near-maximum inlet ebb-tide velocity and depth, Mattituck Inlet
offshore shoal area, 2030 GMT on 7 October 2002
242 Chapter 5 Circulation Analysis
Location A
Location B
Location C
Location DLocation E
Location A
Location B
Location C
Location DLocation E
Location A
Location B
Location C
Location DLocation E
Figure 5-19. Current velocity comparison plot locations
10/910/5 10/810/710/3 10/4 10/6
Location B
Location A
October 2002 GMT
Mattituck Inlet
and Offshore Shoal Area
-3
-2
-1
0
1
2
3
Cu
r
r
e
n
t
v
e
l
o
c
i
t
y
,
m
/
s
e
c
Figure 5-20a. Current velocity at Mattituck Inlet entrance (Locations A and B)
Chapter 5 Circulation Analysis 243
10/910/5 10/810/710/3 10/4 10/6
Mattituck Inlet
and Offshore Shoal Area
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Cu
r
r
e
n
t
v
e
l
o
c
i
t
y
,
m
/
s
e
c
October 2002 GMT
Location E
Location D
Location C
Figure 5-20b. Current velocity between Mattituck Inlet entrance and offshore
shoal (Locations C through E)
Goldsmith Inlet
Water-surface elevation and current velocity at Goldsmith Inlet and
Goldsmith Pond were calculated with the DYNLET model. DYNLET is well
suited for applications to inlet and bay systems not expected to have complex
horizontal circulation patterns. Goldsmith Inlet is such a system in which flow is
directed primarily along the channel. The implicit solution method of DYNLET
can efficiently calculate for shallow water and strong flows, for which an explicit
solution method would require a small time-step. DYNLET can be considered as
a “1-D plus” model in that it solves for current velocity at specified stations along
each cross section as determined by the depth and bottom friction at each station.
Water level at the nodes and velocity at the stations are calculated, with the
velocity apportioned at the stations according to the bottom friction or
conveyance of the channel (Amein and Kraus 1991).
Model validation
A DYNLET bathymetry grid for Goldsmith Inlet was established as a series
of connected nodes that constitute a channel network originating directly offshore
of Goldsmith Inlet and terminating in the back (southern end) of Goldsmith Pond
(Figure 5-21). The model was forced at Node 1with water-level measurements
adapted from the Mattituck Inlet jetty gauge, and a no-discharge boundary
condition (current velocity of zero) was specified at Node 31 located at the back
of the pond. The distance between nodes was determined so as to represent
significant changes in morphology through consideration of channel or pond
width, depth, and roughness of the bottom. The DYNLET grid of Goldsmith
244 Chapter 5 Circulation Analysis
Inlet originates approximately 200 m offshore. The distance between nodes
within the channel and pond is approximately 20 m.
A uniform rectilinear bathymetry grid for Goldsmith Inlet and Goldsmith
Pond was created by importing the October 2002 bathymetry survey data into
DYNLET. Thirty-one nodes with cross sections of varying length were then
generated (Figure 5-21). The October 2002 bathymetry survey is referenced to
NAVD88 datum.
Initial DYNLET validation runs of the Goldsmith Inlet DYNLET model
were not satisfactory because the channel dried occasionally in the simulations.
As discussed in Chapter 4, some locations of the channel have elevations near
msl. The source of the inaccuracy was concluded to be a discrepancy between
the employed NAVD88 datum and msl elevation at Goldsmith Inlet. The
relation between msl and NAVD88 at Goldsmith Inlet and Pond is not known.
The October 2002 bathymetry survey found msl and NAVD88 to be within
survey error offshore of Mattituck Inlet.
Figure 5-21. DYNLET grid of Goldsmith Inlet, with nodes and extents
of nodal cross sections
Chapter 5 Circulation Analysis 245
Water-level measurements obtained offshore of Mattituck Inlet from
19 September to 8 October 2002 drove the model. It was found by numerical
experimentation that raising the water-surface elevation in this data set by 0.25 m
produced a successful model simulation that accurately represented the tidal
signature recorded at Goldsmith Pond, while not drying the channel. The authors
have never observed the inlet channel to dry, even during low tide. DYNLET
model water-level calculations are referenced to NAVD88. The results were
adjusted by subtracting 0.25 m to account for the datum shift of the input water-
surface elevation. A shift upward in the driving water level is functionally
equivalent to shifting the entire bathymetry grid down by the same amount.
DYNLET was calibrated by specifying larger values of the bottom friction
coefficient in the Goldsmith Inlet channel, where small rocks are present and can
protrude above the water surface, some of which may be remnants from jetty
construction. The default value of Manning’s n of 0.025 m/sec1/3 was maintained
at most nodes, but in the channel where rocks and roiling water are seen, the
value was increased to 0.03 to 0.04. The time-step in the model was set to
30 sec.
In initial model runs, calculated water level at the pond gauge lagged the
measurements by 36 min. A lag between calculations and measurements is
expected, because Goldsmith Inlet lies 5 km east of Mattituck Inlet, and the tidal
wave travels from east to west. The tidal record offshore of Mattituck Inlet was
therefore adjusted forward 36 min to account for the time of tidal wave travel
between the location of the tidal record and the location of the input driving the
model. This adjustment implies that the tidal wave moves westward at about
0.23 m/sec along the shallow water of this portion of the north shore of Long
Island.
The input boundary condition (Node 1) and the first DYNLET water-level
calculation (Node 2) for the period of data collection (20 September – 8 October
2002) are plotted in Figure 5-22a. Figure 5-22b shows these water levels for the
5-8 October 2002, spring tide. A comparison of water-level measurements at
Goldsmith Inlet for 20 September – 8 October 2002 and the corresponding
DYNLET calculations (at Node 30) are shown in Figure 5-22c, and Figure 5-22d
gives this comparison for a period of spring tide.
Current velocity measurements taken within Goldsmith Inlet for a short
interval on 8 October are compared to corresponding DYNLET current velocity
calculations (at Nodes 13 and 14) in Figures 5-23a and 5-32b. The calculations
well reproduce the limited length of the measurements. The current velocity is
seen to be strong, exceeding 1 m/sec, and the calculated current is flood
dominant, meaning that the flood current has a higher peak velocity than ebb, but
shorter duration. This dominance has implications for sediment transport in the
inlet, discussed in the following paragraphs.
246 Chapter 5 Circulation Analysis
------ Measurements
------ DYNLET Calculations Node 2
-1.5
-1.0
-0.5
0.0
0.5
Wa
t
e
r
L
e
v
e
l
,
m
1.0
1.5
20 September - 8 October 2002
9/249/20 9/28 10/2 10/6
Goldsmith Inlet Offshore Water Level
Offshore and Node 2
Figure 5-22a. Water-level measurements offshore of Goldsmith Inlet and Node 2
calculations, 20 September - 8 October 2002
------ Measurements
------ DYNLET Calculations Node 2
10/5 10/6 10/7 10/8 10/9
5 - 8 October 2002
-1.5
-1.0
-0.5
0.0
0.5
Wa
t
e
r
L
e
v
e
l
,
m
1.0
1.5 Goldsmith Inlet Offshore Water Level
Offshore and Node 2
Figure 5-22b. Water-level measurements offshore of Goldsmith Inlet and Node 2
calculations, 5-8 October 2002
Chapter 5 Circulation Analysis 247
------ Measurements
------ DYNLET Calculations
20 September - 8 October 2002
-1.0
-0.5
0.0
0.5
1.0
Wa
t
e
r
L
e
v
e
l
,
m
1.5 Goldsmith Pond Water Level
9/20 9/24 9/28 10/2 10/6
Figure 5-22c. Water-level measurements at Goldsmith Pond and DYNLET
Node 30 calculations, 20 September - 8 October 2002
------ Measurements
------ DYNLET Calculations
5 - 8 October 2002
10/910/810/710/610/5-1.0
-0.5
0.0
0.5
1.0
Wa
t
e
r
L
e
v
e
l
,
m
1.5 Goldsmith Pond Water Level
Figure 5-22d. Water-level measurement offshore of Goldsmith Pond and
DYNLET Node 30 calculations, 5-8 October 2002
248 Chapter 5 Circulation Analysis
10/7 10/910/8
Measurements
------- Node 14
------- Node 13
7- 8 October 2002
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
C
u
r
r
e
n
t
V
e
l
o
c
i
t
y
,
m
/
s
e
c
Goldsmith Inlet
Measurements versus Calculations
Figure 5-23a. Current velocity measurement and calculated velocities at
Nodes 13 and 14, 7-8 October 2002
Measurements
------- Node 13
------- Node 14
1100 1200 1600150014001300-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
C
u
r
r
e
n
t
V
e
l
o
c
i
t
y
,
m
/
s
e
c
8 October 2002 (in hours)
Goldsmith Inlet
Measurements versus Calculations
Figure 5-23b. Current velocity measurement and Nodes 13 and 14 calculations,
8 October 2002
Chapter 5 Circulation Analysis 249
Discussion of tidal asymmetry
Table 5-1 lists the mean and maximum depths for the DYNLET nodes.
Depths are referenced to NAVD88 and were extracted from the bathymetry data
of 6-8 October 2002 with a DYNLET interface utility.
Table 5-1
Goldsmith Inlet DYNLET Node Depths
Node Mean Depth (m, NAVD88) Maximum Depth (m, NAVD88)
1 3.57 5.74
2 3.25 5.50
3 2.81 4.23
4 2.36 3.63
5 1.66 2.59
6 0.87 1.98
7 0.71 1.8
8 0.53 1.2
9 0.34 0.50
10 0.31 0.44
11 0.31 0.42
12 0.43 0.61
13 0.46 0.61
14 0.31 0.46
15 0.45 0.63
16 0.3 0.57
17 0.19 0.30
18 0.12 0.15
19 0.14 0.22
20 0.13 0.15
21 0.1 0.14
22 0.52 1.16
23 0.92 1.6
24 1.23 1.84
25 1.29 1.85
26 1.10 1.85
27 1.09 1.83
28 0.91 1.42
29 0.69 1.01
30 0.44 0.90
250 Chapter 5 Circulation Analysis
Calculated tidal water levels exhibit strong asymmetric behavior at
Goldsmith Inlet. Figures 5-24a through 5-24f plot water level at selected nodes
along the inlet channel and the total discharge at each of these nodes. Each
figure plots nodes against the input boundary condition (Node 1) and calculated
elevation at a selected preceding node. The figures contain comparisons for a
spring tide, 5-8 October 2002.
At nodes located near the forcing in Long Island Sound, the water-level
signal is sinusoidal. With distance into the inlet, the water-level signal becomes
more asymmetric, achieving a greater maximum on flood than on ebb, and with a
shorter time of flood than ebb. Such water-level behavior is called flood
dominance. There are three possible contributions the asymmetry. The first and
likely dominant contribution is the presence of sills in the inlet. The higher water
of flood can enter the inlet rapidly, because the tide wave celerity is given by the
square root of the product of gravitational acceleration and depth. On the lower
water of ebb, the depth is less, and the water flow must be slower. Connected
with this hypsometric change in wave speed is the fact that bottom friction will
retard flow more strongly for shallower water.
A second contribution to the asymmetry in water-level signal in the inlet and
pond is the preferential drainage in the wetland surrounding Goldsmith Pond. It
is expected that flooding water will enter the wetland more rapidly than the
draining water on ebb. A third contribution for the asymmetry is the nonlinear
interactions of flow components introduced by the bottom friction terms and
advective terms in the equations of motion.
------ Measurements
------ DYNLET Calculations Node 5
------ DYNLET Calculations Node 8
10/910/810/710/5 10/6
Goldsmith Inlet Calculated Water Level
Offshore, Node 5, Node 8
-1.5
-1.0
-0.5
0.0
0.5
Wa
t
e
r
L
e
v
e
l
,
m
1.0
1.5
5 - 8 October 2002
Figure 5-24a. Water-level measurements offshore of Goldsmith Inlet and
DYNLET Nodes 5 and 8 calculations, 5-8 October 2002
Chapter 5 Circulation Analysis 251
------ Measurements
------ DYNLET Calculations Node8
------ DYNLET Calculations Node 9
10/5 10/6 10/7 10/8 10/9-1.5
-1.0
-0.5
0.0
0.5
Wa
t
e
r
L
e
v
e
l
,
m
1.0
1.5
5 - 8 October 2002
Goldsmith Inlet Calculated Water Level
Offshore, Node 8, Node 9
Figure 5-24b. Water-level measurements offshore of Goldsmith Inlet and
DYNLET Nodes 8 and 9 calculations, 5-8 October 2002
------ Measurements
------ DYNLET Calculations Node 9
------ DYNLET Calculations Node 10
10/910/810/6 10/710/5
Goldsmith Inlet Calculated Water Level
Offshore, Node 9, Node 10
-1.5
-1.0
-0.5
0.0
0.5
Wa
t
e
r
L
e
v
e
l
,
m
1.0
1.5
5 - 8 October 2002
Figure 5-24c. Water-level measurements offshore of Goldsmith Inlet and
DYNLET Nodes 9 and 10 calculations, 5-8 October 2002
252 Chapter 5 Circulation Analysis
------ Measurements
------ DYNLET Calculations Node 10
------ DYNLET Calculations Node 15
10/910/810/710/610/5-1.5
-1.0
-0.5
0.0
0.5
Wa
t
e
r
L
e
v
e
l
,
m
1.0
1.5
5 - 8 October 2002
Goldsmith Inlet Calculated Water Level
Offshore, Node 10, Node 15
Figure 5-24d. Water-level measurements offshore of Goldsmith Inlet and
DYNLET Nodes 10 and 15 calculations, 5-8 October 2002
------ Measurements
------ DYNLET Calculations Node 15
------ DYNLET Calculations Node 20
10/710/6 10/8 10/910/5-1.5
-1.0
-0.5
0.0
0.5
Wa
t
e
r
L
e
v
e
l
,
m
1.0
1.5
5 - 8 October 2002
Water Level
Offshore, Node 15, Node 20
Goldsmith Inlet and Pond Calculated Water Level
Offshore, Node 15, Node 20
Figure 5-24e. Water-level measurements offshore of Goldsmith Inlet and
DYNLET Nodes 15 and 20 calculations, 5-8 October 2002
Chapter 5 Circulation Analysis 253
------ Measurements
------ DYNLET Calculations Node 20
------ DYNLET Calculations Node 30
10/5 10/6 10/7 10/8 10/9-1.5
-1.0
-0.5
0.0
0.5
Wa
t
e
r
L
e
v
e
l
,
m
1.0
1.5
5 - 8 October 2002
Goldsmith Inlet and Pond Calculated Water Level
Offshore, Node 20, Node 30
Figure 5-24f. Water-level measurements offshore of Goldsmith Inlet and
DYNLET Nodes 20 and 30 calculations, 5-8 October 2002
Figures 5-25a to 5-25c plot the total discharge for the nodes referenced in
Figures 5-24a through 5-24e. Flood currents are denoted as positive and ebb
current as negative. The calculated discharge rates in the channel again exhibit a
trend of flood dominance (stronger flood flow for shorter duration than that of
the ebb flow).
10/910/810/710/5 10/6
------ DYNLET Calculations Node 5
------ DYNLET Calculations Node 8
Goldsmith Inlet Calculated Discharge
Node 5 and Node 8
5 - 8 October 2002
-200
-150
-100
-50
0
50
100
150
200
Di
s
c
h
a
r
g
e
,
m
^
3
/
s
e
c
Figure 5-25a. Discharge at Goldsmith Inlet, DYNLET Nodes 5 and 8
calculations, 5-8 October 2002
254 Chapter 5 Circulation Analysis
10/910/810/710/5 10/6
5 - 8 October 2002
-200
-150
-100
-50
0
50
100
150
200
Di
s
c
h
a
r
g
e
,
m
^
3
/
s
e
c
------ DYNLET Calculations Node 9
------ DYNLET Calculations Node 10
Goldsmith Inlet Calculated Discharge
Node 9 and Node 10
Figure 5-25b. Discharge at Goldsmith Inlet, DYNLET Nodes 9 and 10
calculations, 5-8 October 2002
10/910/810/710/5 10/6
5 - 8 October 2002
-200
-150
-100
-50
0
50
100
150
200
Di
s
c
h
a
r
g
e
,
m
^
3
/
s
e
c
------ DYNLET Calculations Node 15
------ DYNLET Calculations Node 20
Goldsmith Inlet Calculated Discharge
Node 15 and Node 20
Figure 5-25c. Discharge at Goldsmith Inlet, DYNLET Nodes 15 and 20
calculations, 5-8 October 2002
Chapter 5 Circulation Analysis 255
Discussion of current velocity
Figures 5-26a through 5-26k plot current velocity at selected nodes across the
DYNLET channel. Each figure displays calculated velocity at selected nodes
and the calculated offshore velocity (Node 1), as well as a calculated velocity at a
selected preceding node exhibiting a significant change in velocity. The plots
contain comparisons for spring tide, 5-8 October 2002. The areas under velocity
curves above and below may not be equal because these curves represent velocity
at one station (one point) at a particular node. The current velocity at other
stations may have different and compensating behavior. In contrast, total
discharge at cross sections (all stations summed) as given in Figures 5-25a to
5-25c must show the same amount of water entering on flood as exiting on ebb
for any tidal cycle (assuming no freshwater inputs to the pond).
The model calculations clearly demonstrate a relationship between limiting
depths at Goldsmith Inlet and maximum velocity through it. Control by limiting
depth is evident at Node 8 during times of flood current and at Nodes 8 and 21
during times of ebb current. Maximum calculated current velocity within the
channel at Goldsmith Inlet increases by an order of magnitude between nodes as
the flow enters the inlet mouth between Nodes 6 and 7, owing to the constriction
and decrease in depth. At Node 7, the inlet mouth, the flow is still predominantly
sinusoidal, but with a shift toward flood dominance. With distance into the inlet,
similar to findings for calculated water level, the signal for the current velocity
becomes more flood dominant.
10/810/710/6 10/910/5
------- Node 6
------- Node 7
Node 1
5 - 8 October 2002
-1.8
-1.2
-0.6
0.0
0.6
1.2
1.8
Cu
r
r
e
n
t
V
e
l
o
c
i
t
y
,
m
/
s
e
c
Goldsmith Inlet
Figure 5-26a. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 6 and 7 calculations, 5-8 October 2002
256 Chapter 5 Circulation Analysis
10/810/710/6 10/910/5
------- Node 7
------- Node 8
Node 1
5 - 8 October 2002
-1.8
-1.2
-0.6
0.0
0.6
1.2
1.8
Cu
r
r
e
n
t
V
e
l
o
c
i
t
y
,
m
/
s
e
c
Goldsmith Inlet
Figure 5-26b. Current velocity calculations offshore of Goldsmith Inlet and
DYNLET Nodes 7 and 8 calculations, 5-8 October 2002
10/810/710/6 10/910/5
------- Node 8
------- Node 9
Node 1
5 - 8 October 2002
-1.8
-1.2
-0.6
0.0
0.6
1.2
1.8
Cu
r
r
e
n
t
V
e
l
o
c
i
t
y
,
m
/
s
e
c
Goldsmith Inlet
Figure 5-26c. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 8 and 9 calculations, 5-8 October 2002
Chapter 5 Circulation Analysis 257
10/810/710/6 10/9 10/5
------- Node 10 ------- Node 9 Node 1
5 - 8 October
-1.8
-1.2
-0.6
0.0
0.6
1.2
1.8
Cu
r
r
e
n
t
V
e
l
o
c
i
t
y
,
m
/
s
e
c
Goldsmith
Figure 5-26d. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 9 and 10 calculations, 5-8 October 2002
10/810/710/6 10/910/5
Node 1
------- Node 10
------- Node 11
5 - 8 October 2002
Goldsmith Inlet
-1.8
-1.2
-0.6
0.0
0.6
1.2
1.8
Cu
r
r
e
n
t
V
e
l
o
c
i
t
y
,
m
/
s
e
c
Figure 5-26e. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 10 and 11 calculations, 5-8 October 2002
258 Chapter 5 Circulation Analysis
10/810/710/6 10/910/5
------- Node 13
------- Node 11
Node 1
5 - 8 October 2002
-1.8
-1.2
-0.6
0.0
0.6
1.2
1.8
Cu
r
r
e
n
t
V
e
l
o
c
i
t
y
,
m
/
s
e
c
Goldsmith Inlet
Figure 5-26f. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 11 and 13 calculations, 5-8 October 2002
10/810/710/6 10/910/5
------- Node 16
------- Node 13
Node 1
5 - 8 October 2002
Goldsmith Inlet
-1.8
-1.2
-0.6
0.0
0.6
1.2
1.8
Cu
r
r
e
n
t
V
e
l
o
c
i
t
y
,
m
/
s
e
c
Figure 5-26g. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 13 and 16 calculations, 5-8 October 2002
Chapter 5 Circulation Analysis 259
10/810/710/6 10/910/5
------- Node 16
------- Node 17
Node 1
5 - 8 October 2002
-1.8
-1.2
-0.6
0.0
0.6
1.2
1.8
Cu
r
r
e
n
t
V
e
l
o
c
i
t
y
,
m
/
s
e
c
Goldsmith Inlet
Figure 5-26h. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 16 and 17 calculations, 5-8 October 2002
10/810/710/6 10/910/5
------- Node 17
------- Node 21
Node 1
5 - 8 October 2002
-1.8
-1.2
-0.6
0.0
0.6
1.2
1.8
Cu
r
r
e
n
t
V
e
l
o
c
i
t
y
,
m
/
s
e
c
Goldsmith Inlet
Figure 5-26i. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 17 and 21 calculations, 5-8 October 2002
260 Chapter 5 Circulation Analysis
10/810/710/6 10/910/5
------- Node 22
------- Node 21
Node 1Goldsmith Inlet
5 - 8 October 2002
-1.8
-1.2
-0.6
0.0
0.6
1.2
1.8
Cu
r
r
e
n
t
V
e
l
o
c
i
t
y
,
m
/
s
e
c
Figure 5-26j. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 21 and 22 calculations, 5-8 October 2002
10/810/710/6 10/910/5
------- Node 30
------- Node 22
Node 1
5 - 8 October 2002
Goldsmith Inlet
-1.8
-1.2
-0.6
0.0
0.6
1.2
1.8
Cu
r
r
e
n
t
V
e
l
o
c
i
t
y
,
m
/
s
e
c
Figure 5-26k. Current velocity calculations offshore of Goldsmith Pond and
DYNLET Nodes 22 and 30 calculations, 5-8 October 2002
Chapter 5 Circulation Analysis 261
Figure 5-27 plots the maximum calculated velocity at each node for a spring
flood tide and the subsequent ebb tide on 7 October 2002, together with the
elevation. The flood current had maximum velocity of 1.43 m/sec for this time
interval. Strong flood-tidal currents persist to the exit of the channel into
Goldsmith Pond. The ebb current at the mouth exceeds 1 m/sec.
0 8 16 20 25 3061 2
Ebb
Elevation
Flood
0 100 200 300 400 500 600 700
Distance along Dynlet Channel (m)
Node numbers below in red
-4
-3
-2
-1
0
1
2
3
4
Cu
r
r
e
n
t
V
e
l
o
c
i
t
y
,
m
/
s
e
c
E
l
e
v
a
t
i
o
n
,
m
N
A
V
D
8
8
Figure 5-27. Maximum calculated flood- and ebb-spring-tide current speed and
water elevation at Goldsmith Inlet, 7 October 2002
Figure 5-28a and 5-28b display composite surfaces of maximum calculated
flood and ebb velocity, respectively, at all node stations for hours 400 to 450 of
the model run. Larger-scale views of these velocities within the channel are
shown in Figures 5-28c and 5-28d. The time interval corresponds to 7-8 October
2002, a spring tide, giving maximum velocities experienced at these locations.
Figure 5-28e shows a difference map between these surfaces that illustrates the
magnitude of current velocity asymmetry throughout the surface.
A strong flood current persists over the entire channel and into the pond,
whereas the ebb current is weak over much of the channel and pond, except at the
mouth of the inlet. Such behavior would tend to transport sediment, particular
sand, toward Goldsmith Pond, promoting flood shoal development and growth.
The strong ebb current at the entrance would tend to maintain the inlet by
sweeping finer sediments away from the mouth. However, sediment brought into
the inlet on flood will not be flushed on ebb, promoting closure by constriction
inside the inlet and not necessarily at the mouth.
262 Chapter 5 Circulation Analysis
Figure 5-28a. Goldsmith Inlet spring flood-tide maximum current velocity, total
calculation domain
Figure 5-28b. Goldsmith Inlet spring ebb-tide maximum current velocity, total
calculation domain
Chapter 5 Circulation Analysis 263
Figure 5-28c. Goldsmith Inlet spring flood-tide maximum current velocity,
inlet channel
Figure 5-28d. Goldsmith Inlet spring ebb-tide maximum current velocity,
inlet channel
264 Chapter 5 Circulation Analysis
Figure 5-28e. Goldsmith Inlet spring flood-tide and ebb-tide maximum
current velocity difference
Chapter 6 Inlet Morphology and Stability 265
6 Inlet Morphology and
Stability
The morphology of an inlet is a consequence of a dynamic balance among
the factors of hydrodynamic forcing, geologic setting, supply and transport of
sediment in and near the inlet, and any artificial manipulations such as jetty
construction and dredging. Classification methods describing the large-scale
features of inlets (ebb shoal, flood shoal and inlet channel) are available (e.g.,
Bruun and Gerritsen 1959, 1960; Hayes 1980). Empirical relations have been
derived that relate the tidal prism of an inlet to its channel cross-sectional area
(e.g., LeConte 1905; O’Brien 1931, 1966; Jarrett 1976; Byrne et al. 1980), and a
method for estimating inlet channel cross-sectional area stability is also available
(Escoffier 1940). Jarrett (1976) and Byrne et al. (1980) examined the width-to-
depth ratio W/D of inlet channels to characterize the hydraulic efficiency.
Relations have been also been derived to predict the volume of inlet ebb shoals
(Walton and Adams 1976) and flood shoals Carr de Betts (1999) based on tidal
prism.
In this chapter, the channel and shoal morphologies of Mattituck Inlet and
Goldsmith Inlet are examined through available qualitative and quantitative
approaches, incorporating data and calculation results presented in preceding
chapters.
General Inlet Properties
Studies that explore the quantitative properties of morphologic features of
inlets are reviewed in this section as preparation for application to Mattituck Inlet
and Goldsmith Inlet.
Inlet classification and sedimentation patterns
Hayes (1977) and Davis and Hayes (1984) introduced a classification
procedure that places inlet morphology within a continuum ranging from tide
dominated to wave dominated (Figure 6-1). At tide-dominated inlets, ebb shoals
tend to be large (relative to the flood shoal) and intertidal at their crests.
Sediment (sand) bypassing occurs through the mechanism of “tidal bypassing,”
(Bruun and Gerritsen 1959, 1960) by which sediment is initially brought into the
inlet from the updrift side by the flood tide and then transported to the downdrift
side by the ebb current. Mattituck Inlet and Goldsmith Inlet fall into the category
of tide-dominate inlets according to Figure 6-1. However, there is a large gravel
266 Chapter 6 Inlet Morphology and Stability
and coarse-grained sediment component at these inlets that will minimize tidal
bypassing, and these inlets do not possess an ebb shoal because of the large grain
size of the sediment, weak wave action, and weak ebb discharges.
T i d e –D o m i n a t e d
(h i g h )
T i d e –D o m i n a t e d (l o w )
M i x e d E n e r g y
(t i d e d o m i n a t e d )
M i x ed E n e r gy
(w a v e d om i n at e d)
W a v e D o m i n a t e d
A p p r o x . l i m i t o f b a r r i e r f o r m a t i o n
01 2
0
5
4
3
2
1
6
Mean Wave Height, m
Me
a
n
T
i
d
a
l
R
a
n
g
e
,
m
Mattituck Inlet
Goldsmith Inlet
T i d e –D o m i n a t e d
(h i g h )
T i d e –D o m i n a t e d (l o w )
M i x e d E n e r g y
(t i d e d o m i n a t e d )
M i x ed E n e r gy
(w a v e d om i n at e d)
W a v e D o m i n a t e d
A p p r o x . l i m i t o f b a r r i e r f o r m a t i o n
01 2
0
5
4
3
2
1
6
Mean Wave Height, m
Me
a
n
T
i
d
a
l
R
a
n
g
e
,
m
Mattituck Inlet
Goldsmith Inlet
Figure 6-1. Classification of tidal inlet morphology (after Davis and Hayes 1984)
Sand bypassing at tide-dominated inlets can also occur by breaching and
reconfiguring of the ebb shoal as the outer inlet channel meanders. This process
pertains to inlets without stabilization structures. Breaching and reconfiguration
combined with wave-driven onshore migration of sand bodies in the form of
swash bars can result in large volumes of sand bypassed from the ebb shoal to the
adjacent beaches (FitzGerald et al. 2000). In this process, the channel elongates
while typically migrating downdrift. Hydraulic friction of the long channel
reduces the inlet current that acts to maintain the inlet entrance; eventually,
sediment brought to the entrance by waves closes it. The blocked flow will then
break through at a narrow point in the spit located closer to the main channel
prior to migration, thereby starting a possible repeat of the cycle of migration,
closure, and reopening. This cyclic process may have acted at both Mattituck
Inlet and Goldsmith Inlet prior to their stabilization. It probably could not occur
at the present Goldsmith Inlet because of the wide beach segment located to the
west, adjacent to the jetty.
In contrast, wave-dominated inlets have small ebb shoals that are submerged,
and well-developed flood shoals that can be emergent at low tide. Natural sand
bypassing occurs through “bar bypassing,” the mechanism of wave-driven
transport across the outer bar of the ebb shoal to downdrift bypass and
attachment bars. The typical morphology of the ebb shoal of an inlet has been
identified as an ebb shoal proper, which lies directly in front of the inlet, close to
Chapter 6 Inlet Morphology and Stability 267
the channel or within ebb tidal jet flow, together with bypassing bars on each side
with volumes dependant on the balance of left-directed and right-directed
longshore transport (Kraus 2000). At wave-dominated inlets, the longshore
transport of sediment occurs by exchange of sediment among these morphologic
components of the ebb shoal system. Inspection of the morphology at Goldsmith
Inlet indicates that sediment bypasses the mouth under wave action, but without
apparent ebb shoal or bypass bar to the east.
A third type of bypassing, episodic bypassing, occurs when large portions of
sediment detach from the ebb shoal complex and migrate to shore (FitzGerald
1988; Gaudiano and Kana 2000). Episodic bypassing is not applicable to
Mattituck Inlet and Goldsmith Inlet, because these inlets do not have ebb-tidal
shoals or significant bypassing bars.
Bruun and Gerritsen (1959, 1960) first identified the mechanisms of
bypassing by littoral transport across the outer bar (ebb shoal complex) and tidal
bypassing. They defined a ratio r as:
g
PrQ= (6-1)
where P.= tidal prism, and Qg = gross or total longshore sediment transport rate
in 1 year (giving a volume). The tidal prism in this relation corresponds to spring
tide, when the strongest current scours the inlet channel. The parameter r
expresses the relative strength of the tidal flow that acts to sweep the inlet clear
of sediment brought into its entrance by wave-generated longshore sediment
transport. Based on the observations of Bruun and Gerritsen (1959, 1960), the r
ratio allows for classification of inlet channel stability and mode of sand
bypassing. Inlet characteristics associated with different r ratio ranges are
summarized in Table 6-1. Inlets with low r-values have channels that are
unstable experience bar bypassing (wave-dominated inlets), whereas inlets with
large r-values tend to have stable channels and experience tidal bypassing (tide-
dominated inlets).
Table 6-1
Inlet Bypassing and Channel Cross-Sectional Stability
Classification of Inlets (Modified from Bruun and Gerritsen (1959,
1960) and Including Additional Information)
r-value Channel Stability Dominant Bypassing Mode
r < 20 Unstable. Inlet may be closed by
deposition of sediment during a
storm. Typically no navigable
channel.
Bar bypassing
r = 20-50 Highly variable in location and area,
with multiple channels possible.
Dredging and jetties typically required
to maintain navigable depths.
Bar bypassing; may have several bars
r = 50-150 Clear main channel and well-
developed ebb shoal.
Bar bypassing and tidal bypassing
r > 150 Reasonably stable channel. Episodic bypassing, tidal bypassing
268 Chapter 6 Inlet Morphology and Stability
Inlet Stability
Quantitative empirical relations between the equilibrium, or minimal stable
cross-sectional channel area of an inlet and its tidal prism have been established
for almost a century (e.g., LeConte 1905; O’Brien 1931, 1969; Jarrett 1976).
This relation is expressed as:
n
CAC P= (6-2)
where AC = minimum inlet cross-sectional channel area below msl, and C and
n = empirical coefficients determined from field measurements.
The original expression has undergone refinement as measurements have
become available. Research has been performed to better estimate the empirical
coefficients, taking into account processes such as wave activity, degree of
sheltering of the inlet from waves, presence or absence of jetties, inlet channel
cross-section size, and sediment size. Jarrett (1976) analyzed 108 tidal inlets
along the three oceanic coasts of the United States and quantified variations in
this relation based on location and the number of jetties as none, one, or two.
Table 6-2 lists the empirical coefficient values derived by Jarrett (1976). The
108 inlets examined were located on sandy (fine to medium sand) coasts.
Table 6-2
Tidal Prism (cu ft) and Minimum Channel Cross-Sectional Area
(sq ft) Relationships (Jarrett 1976)
Location All Inlets
Unjettied,
Single jettied Dual Jettied
All Inlets Ac = 5.74 x 10 –5 P 0.95 Ac = 1.04 x 10 –5 P 1.03 Ac = 3.76 x 10 –4 P 0.86
Atlantic Coast Ac = 7.75 x 10 –6 P 1.05 Ac = 5.37 x 10 –6 P 1.07 Ac = 5.77 x 10 –5 P 0.95
Gulf Coast Ac = 5.02 x 10 –4 P 0.85 Ac = 3.51 x 10 –4 P 0.86 Insufficient data
Pacific Coast Ac = 1.19 x 10 –4 P 0.91 Ac = 1.91 x 10 –6 P 1.10 Ac = 5.28 x 10 –4 P 0.85
Simpson (1976) investigated the hydraulics of two small gravelly inlets
located within Puget Sound, WA, and found that the cross-sectional area of both
inlets was smaller than the equilibrium area predicted by previously derived
expressions. Byrne et al. (1980) investigated 14 small inlets they defined by the
criterion Ac < 100 sq m (1,076 sq ft). These inlets were located within lower
Chesapeake Bay, VA, on sandy shores and were not stabilized by structures.
They quantified a departure from previously derived coefficients based on inlet
size. This relation, expressed in American Customary Units, was found to be:
20 . 6 11.212 10CAP−=× (6-3)
Byrne et al. (1980) compared their data set to that compiled by Jarrett (1976) and
concluded that for small inlets, the departure from the tidal prism – minimum
channel cross-sectional area relation derived for larger oceanic inlets occurs
between Ac = 100 and 500 sq m (1,076 and 5,082 sq ft).
Chapter 6 Inlet Morphology and Stability 269
Escoffier (1940) analyzed closure conditions for a tidal inlet channel by
comparing possible cross-sectional areas of the inlet with those predicted by a
stability criterion such as given in Equation 6-2. As noted by Seabergh (2003),
equilibrium cross-sectional area predicted through an Escoffier analysis implies
that the amplitude of the water-surface elevation in the bay is close or equal to
the amplitude in the tidal body connected to the inlet.
Kraus (1998) derived the form of Equation 6-2 through a process-based
model that accounts for the dynamic balance between ebb-tidal sediment
transport and the longshore sediment transport produced by waves. The power of
n in Equation 6-2 was found to be 0.9, in agreement with values listed in
Table 6-2, and the coefficient C was determined to be of the form:
0.332 4 / 3
3
π ME
g
nWCQT
α=⎛⎞⎜⎟⎝⎠
(6-4)
where
α = nondimensional coefficient with value of order unity entering the inlet
sediment transport formula employed
2
Mn = Manning’s roughness coefficient squared, sec2/m2/3
WE = width of inlet at equilibrium, m
Qg = annually gross longshore transport rate, cu m/year (converted to
cu m/sec)
T = dominant tidal period, which is 44,712 sec for a semidiurnal tide
Equation 6-4 does not explicitly account for a threshold of motion for
transport by the ebb-tidal current or by the longshore sediment transport rate. A
threshold could be significant for gravel and cobble beaches, both for transport
by the tidal current in the inlet and by waves at and adjacent to the inlet.
Equation 6-4 indicates that the value of C will increase if the gross longshore
transport rate decreases, all other factors being equal, giving a larger value of the
cross-sectional area AC in Equation 6-2 for the same tidal prism P.
Hydraulic efficiency
Jarrett (1976) compiled information on the ratios of inlet width, W to depth,
D for the 108 inlets he studied. He found that inlets with smaller W/D ratios
(<100) tend to be hydraulically more efficient. This result is reasonable, because
small W/D values indicate relatively greater depth, hence weaker bottom friction.
A more hydraulically efficient channel implies a larger channel cross section for
the same tidal prism. The average W/D ratio for all the inlets studied by Jarrett
(1976) was 337, and the average W/D ratio for the 16 Atlantic coast dual-jettied
inlets was 67.
Byrne et al. (1980) compiled information on W/D for their 14 studied inlets
located in Chesapeake Bay and obtained an average W/D = 23. They conclude
that the cross section of smaller channels must, therefore, become more efficient
than that of larger channels to maintain stability. The observed departure in W/D
characteristics between large and small inlets occurs between approximately AC =
100 sq m to 500 sq m (1,076 sq ft to 5,082 sq ft).
270 Chapter 6 Inlet Morphology and Stability
Ebb shoal volume
Walton and Adams (1976) derived empirical equations based on analysis of
42 inlets that relate the volume of the ebb shoal of a mature or equilibrium inlet
to its tidal prism. This relation can be expressed as
VE = CE P 1.23 (6-5)
where VE = volume of the ebb shoal in cu yd, and P = tidal prism in cu ft. The
value of the empirical coefficient CE depends on wave exposure as CE = 8.7
× 10-5 for highly exposed coasts (typically, Pacific Ocean coast), 10.5 × 10-5 for
moderately exposed coasts (typically, northern Atlantic Ocean coast), 13.8 × 10-5
for mildly exposed coasts (typically, Gulf of Mexico and southern Atlantic
coast), and 10.7 × 10-5 for all coasts.
Flood shoal volume
Carr de Betts (1999) derived empirical predictive relations that relate the
volume and area of the flood shoal of an inlet to its spring tidal prism. She
studied 61 inlets in Florida, 19 of them located along the Atlantic coast and 42
along the Gulf of Mexico coast. It is noted here that inlets of Florida lie on
coasts containing abundant quantities of fine sand (and small shell fragments in
the case of the gulf coast of Florida). Flood shoals would be expected to more
easily form in coastal environments with plentiful fine material, in contrast to the
coarser sediments found along the north shore of Long Island, NY.
Predictive expressions were developed for the near field (that part of the
flood shoal readily visible), far field (that part spread in a thin layer further in the
bay), and total flood shoal combining the near and far fields (Carr de Betts 1999).
The predictive relation between inlet tidal prism and total volume of the flood
shoal is:
VFT = 2.0389 x 104 P 0.296 (6-6)
where VFT = total volume of the total flood shoal in cu m, and P = the tidal prism
in cubic meters. The predictive relation between inlet tidal prism and total area
of the associated flood shoal is:
AFT = 4.7585 x 104 P 0.249 (6-7)
where AFT = total area of the flood shoal in square meters.
The predictive relationships between the tidal prism and the near field flood shoal
volume and area is used to estimate flood shoal area and volume at Mattituck
Inlet and Goldsmith Inlet later in this chapter. The predictive relationships
between the tidal prism and the far field flood shoal volume and area is not used
and is not shown here. The predictive relation between inlet tidal prism and near
field volume of the flood shoal is:
VFN = 4.056 × 103 P 0.314 (6-8)
where VFN = near field volume of the flood shoal in cu m, and P = the tidal prism
in cubic meters. The predictive relation between inlet tidal prism and near field
area of the associated flood shoal is:
AFN = 1.4532 x 104 P 0.254 (6-9)
Chapter 6 Inlet Morphology and Stability 271
where AFN = near field area of the flood shoal in square meters.
The regression correlations for these relations were weak. In contrast to an
ebb shoal, there is no significant wave force acting against the flood-tidal jet,
allowing sediment to travel far into an inlet and spread in a thin layer that is
difficult to measure. Older portions of flood shoals are difficult to distinguish
from peripheral wetlands and marshes. Flood shoals are also manipulated
through dredging. These empirical relations, however, can be useful in obtaining
order-of-magnitude estimates.
Mattituck Inlet
Material introduced in the preceding sections of this chapter is applied to
Mattituck Inlet in this section and to Goldsmith Inlet in the following section.
According to the classification by Davis and Hayes (1984), shown in
Figure 6-1, Mattituck Inlet is a tide-dominated inlet because it experiences
forcing by a diurnal mean tidal range of approximately 1.6 m and is subject to a
relatively small mean wave height. Given the limited fetch of Long Island
Sound, the mean annual wave height for non-calm events (when waves are
present) for Mattituck Inlet is estimated to be 0.3 m and consists mainly of steep
wind waves that would tend to move finer sand offshore (Batten and Kraus
2005).
Hubbard et al. (1979) classified tidal inlet morphology based on the
hydrodynamic setting. Tide-dominated inlets have well-developed ebb shoals,
and sand bypassing is accomplished through tidal bypassing. It has been
concluded in this study that the linear shoal located offshore of Mattituck Inlet is
not an ebb shoal. Evidence of tidal bypassing, however, can be seen in the depth
contours between this feature and the entrance channel (Figure 3-16).
Table 6-3 lists values to calculate the r ratio for Mattituck Inlet. The tidal
prism was calculated by multiplying the bay area of the inlet by its spring tidal
range. The surface area of Mattituck Inlet and Mattituck Creek was
7.2 × 106 sq ft as interpreted from GIS analysis of an aerial photograph dated 16
April 2003. The spring tide range within the creek was 6.0 ft based on water-
level data collected 19 September to 8 October 2002, consistent with the value
given by NOS for the area.
Because the gross longshore sediment transport rate at Mattituck Inlet is not
well known, two values (15,000 and 25,000 cu yd/year) were used to calculate
the r ratio of Mattituck Inlet. These values are considered to represent the
minimum and maximum gross longshore sediment transport rates at the inlet.
Mattituck Inlet has an r ratio of in the range of 64 to 107 (Table 6-3). According
to the classification of Bruun and Gerritsen (1959, 1960) summarized in
Table 6-1, inlets with an r ratio of 50 to 150 have a well-developed ebb shoal
(sandy beaches), and sand bypassing occurs through a combination of bar
bypassing and tidal bypassing. Mattituck Inlet lacks an ebb shoal. However,
sediment bypassing from the west beach may occur along the offshore shoal, and
it is inferred to occur along a bypassing bar located near the tip of the west jetty.
It is feasible that fine to medium sand can bypass in this way, but not coarser
sand and gravel because of the small waves and weak tidal current (Chapter 5).
The sand bypassing complex offshore of Mattituck Inlet is displayed in Figure 3-
272 Chapter 6 Inlet Morphology and Stability
14. Sand bypassing at Mattituck Inlet appears to occur through a combination of
tidal bypassing and bar bypassing.
Table 6-3
Mattituck Inlet r Ratio and Associated Physical Quantities
Quantity Mattituck Inlet
Tidal range (ft) 6.0
Surface area (sq ft) 7.2 ×106
Tidal Prism (cu ft) 4.32 × 107
Longshore transport rate (cu yd)1 15,000 -25,000
r ratio 64-107
1 Range in longshore sediment transport rate accounts for estimated range in east-directed
transport, material directed to the offshore by the west jetty, and efficiency of the present east jetty to
block sediment directed at the inlet from the east.
The relatively short distance between the jetties, promotes scouring flow in
the channel (small W/D ratio). For Mattituck Inlet, W/D = 43, calculated by
dividing the width of the inlet between the two jetties (400 ft) by the measured
hydraulic radius (9.3 ft). Jarrett (1976) notes that inlets with small W/D ratios
(W/D <100) are hydraulically efficient.
Mattituck Inlet channel cross-sectional area stability
The Channel Equilibrium Area (CEA) model (Seabergh and Kraus 1997)
creates an Escoffier stability curve for a given inlet and was applied to examine
stability of Mattituck Inlet. The Jarrett (1976) relation for dual-jettied inlets on
the Atlantic coast was selected for the analysis, of which Mattituck Inlet fits well
to the trend (Figure 6-2). The one-dimensional CEA model is calibrated by
inputting the dimensions of the inlet and bay from which the hydrodynamics of
the inlet are calculated. The CEA model requires the tidal amplitude at an inlet,
which is half the tidal range.
CEA-calculated water level and velocity are then compared to measurements
at the inlet. Figure 6-3 plots measured and calculated water levels offshore of
Mattituck Inlet, and Figure 6-4 plots measured and calculated water levels for
within the inlet. The comparison period 5-7 October 2002 was selected because
the measurement range was nearly equal to the spring tide range as reported by
the NOS (6.0 ft) (Chapter 3).
Table 6-4 summarizes the physical quantities that served as input to calculate
the equilibrium channel area of Mattituck Inlet. The minimum cross-sectional
area of 1,600 sq ft was derived from the cross sections produced from the
bathymetry survey of 6-8 October 2002. The cross section used, cross-section 9,
is shown in Figure 3-20c. Cross-section 8 appears to have a smaller area, but
was not selected because of inadequate survey coverage. The location of this
transect, at the main area of shoaling, is shown in Figure 3-19.
Chapter 6 Inlet Morphology and Stability 273
102
103
104
105
106
Ch
a
n
n
e
l
A
r
e
a
,
s
q
f
t
106 107 108 109 1010 1011
Tidal Prism, cu ft
Jarrett regression equation
Mattituck Inlet
Atlantic coast dual-jettied inlets
Figure 6-2. Tidal prism-channel area relation, Mattiuck Inlet and Atlantic
coast dual jettied inlets
1200 1200 120024002400
7 October 2002 GMT
Calculated___
- - - Measured
6 October
-4
-3
-2
-1
0
1
Wa
t
e
r
L
e
v
e
l
,
f
t
N
A
V
D
8
8
2
3
4
5 October
Offshore Water Level
Figure 6-3. Mattituck Inlet offshore water-level measurements and calculations
by CEA model
274 Chapter 6 Inlet Morphology and Stability
1200 1200 120024002400
7 October 2002 GMT
Measured
Calculated___
- - -
-4
-3
-2
-1
0
1
Wa
t
e
r
L
e
v
e
l
,
f
t
N
A
V
D
8
8
2
3
4 Mattituck Creek Water Level
5 October 6 October
Figure 6-4. Mattituck Creek water-level measurements and calculations by CEA
model
Table 6-4
Channel Equilibrium Area Model Quantities for Mattituck Inlet
Ocean tide amplitude (ft) 3.0 Channel length (ft) 3,000
Bay surface area (sq ft) 7.2 x 106 Channel width (ft) 200
Hydraulic radius (ft) 9.3 Channel area (sq ft) 1,600
The calibrated CEA model produced the stability curve shown in Figure 6-5,
giving a predicted stable equilibrium area of 1,020 ft for Mattituck Inlet. In an
Escoffier inlet stability analysis, if the calculated velocity for the inlet falls below
the equilibrium velocity (or is tangent to it at a single point), the inlet is unstable
and will close. If the two curves intersect at two points (as for Mattituck Inlet),
the point on the right is identified as the stable equilibrium cross-sectional area.
If the channel area is larger than this, the tidal current velocity in the inlet will
decrease, promoting channel infilling and a return to the stable condition. If the
channel area decreases, the tidal current velocity in the inlet will increase,
scouring the channel until it returns to stable cross-sectional area. The
intersection on the left side of the Escoffier curve denotes an unstable condition.
If the channel area decreases beyond this point, velocity will decrease and the
inlet will tend toward closure because friction will reduce the velocity further.
Chapter 6 Inlet Morphology and Stability 275
E q u i l i b r i u m
C a l c u l a t e d
1,020 sq ft
E q u i l i b r i u m
C a l c u l a t e d
1,020 sq ft
Figure 6-5. Escoffier curve calculated for Mattituck Inlet, CEA model
The Jarrett (1976) relation predicts an msl minimum stable channel cross-
sectional area of 1,035 sq ft for Mattituck Inlet. The Escoffier analysis of
Mattituck Inlet predicts a stable channel cross-sectional area of 1,020 sq ft, which
is 36 percent smaller than the observed October 2002 measurement of
1,600 sq ft.
The measured inlet channel cross-sectional area is significantly larger than
predicted. The Escoffier stability analysis is based on the implicit assumption
that the bay tide range will approach or equal the ocean or forcing tide range
(Seabergh 2003). This is not the case for Mattituck Inlet, yet the channel cross-
sectional area is greater. Such a morphological property, a much larger-than-
predicted inlet channel cross-sectional area, is anomalous.
Several factors might contribute to the unusually large channel cross-
sectional area. In the judgment of the authors, in possible order of significance,
these are:
a. Historic mining of the inlet channel and the adjacent west beach may
have removed at least 500,000 cu yd of sand and gravel over an
approximate 50-year period (1920s to 1970s), artificially increasing the
area and hydraulic efficiency of the entrance channel.
b. The relatively low longshore sediment transport rate found on the north
shore of Long Island and at this site, due to its shoreline orientation and
protection by the west jetty, is not adequate to fill a maintained channel.
c. The relatively small W/D ratio of 43, indicating hydraulically efficient
inlet (for fine-and medium-sized sand).
Mattituck Inlet offshore shoal
To further explore the origin of the linear offshore shoal located east of
Mattituck Inlet, that is, whether or not it is an ebb-tidal shoal, the empirical
276 Chapter 6 Inlet Morphology and Stability
prediction of Walton and Adams (1976) was examined. The coefficient value
CE = 8.7 × 10–5 (Equation 6-5) for mildly exposed coasts was employed in the
calculation. For the tidal prism of 4.32 × 107 cu ft, the volume of the shoal is
predicted to be 340,000 cu yd. The actual volume of this feature was calculated
to be 460,000 cu yd (Chapter 4).
The difference between the actual and predicted volume of this feature
supports a conclusion that the feature is not a relic or active ebb-tidal shoal.
Implicit in the estimation procedure of Walton and Adams (1976) is the
requirement that the sediment at a site be predominantly fine to medium sand.
Because the offshore shoal considered contains a significant percentage of coarse
sand and gravel, it is expected that the Walton and Adams (1976) empirical
relation would overestimate the volume if the feature were an ebb shoal. The
underestimation of the shoal volume by the Walton and Adams (1976) relation
supports the conclusion that this feature is not an ebb shoal.
Other aspects of this study further support this conclusion. The shoal is
located too far east (outside the ebb-tidal jet) and possesses large gravel content,
making transport of these sediment grains from the inlet to the feature doubtful.
Tidal circulation modeling of Mattituck Inlet (Chapter 5) indicates that the
feature is not hydraulically connected to the inlet in its present condition or in its
natural condition. Finally, the feature experienced minimal growth between 1927
and 2002 (Chapter 4).
Mattituck Inlet flood shoal
The volume of the flood shoal at Mattituck Inlet can be estimated directly
through bathymetry difference calculations in a GIS and compared to the
empirical relation derived by Carr de Betts (1999).
The major area of shoaling at Mattituck Inlet is found on the east bank
adjacent to the end of the east jetty, and there is also considerable shoaling on the
opposite (west) bank. The shoaling refers to locations above the navigation
channel and does not include deposition along the walls of the channel (bank
encroachment). Shoaling inferred to be caused by the transport of sediment into
Mattituck Inlet continues along both banks to a distance of about 2,000 ft beyond
the landward end of the inlet.
A polygon that encompasses this area was created in a GIS, and a TIN was
generated (Figure 6-6). The extent of the flood shoal considered here is greater
than the preceding analysis of flood shoal morphology change. Morphology
change analysis was based on the area of the flood shoal included in typical New
York District condition surveys. Because the bathymetry survey of 6-8 October
2002 covered all of Mattituck Creek, the area of analysis is extended here. An
estimate of the volume of this portion of the flood shoal was obtained by
calculating the volume of sediment found above a reference datum. Two
volumes with respect to two reference datums (-6 ft NAVD88 and –4 NAVD88,
which correspond approximately to –3 ft mlw and –1 ft mlw) were calculated to
provide an estimated range of the volume of this portion of the flood shoal.
The area considered to be part of the flood shoal included dry land to an
elevation of up to +1.5 ft NAVD88. This identification was made because
analysis of historical aerial photographs indicated that these areas are new
features created by shoaling and landward bypassing accumulation (Figures 4-24
Chapter 6 Inlet Morphology and Stability 277
through 4-26b and Figures 4-37a through 4-37b). In some areas, however,
portions of dry land that may be within the intertidal zone, and part of the flood
shoal, were not covered by the survey. The surface area range of the 6-8 October
2002 flood shoal was calculated as 1.99 × 105 to 2.68 × 105 sq ft. The volume
range was calculated to be 1.58 × 104 to 3.26 × 104 cu yd.
Bank encroachment is a significant form or mode of shoaling at Mattituck
Inlet and occurs along the east channel wall. Analysis of pre-dredging surveys
indicates that the length of the east channel wall subject to bank encroachment is
approximately 1,000 ft. The project slope for the Mattituck Inlet navigation
channel is 1:3. The resulting surface area of the east channel wall subject to
encroachment is approximately 1.0 × 104 sq ft. Based on the analysis of temporal
changes in channel width (Figures 4-39a through 4-39c), the 1,000-ft-long
section of the east channel wall is estimated to be subject to an overall depth-
averaged rate of sediment accumulation of 2 ft/year. This rate of encroachment
converts to 740 cu yd/year of sediment accumulation on the east channel wall.
Figure 6-6. Shoaling at Mattituck Inlet and Mattituck Creek, 6-8 October 2002
Analysis of pre-dredging surveys indicates that the length of the west
channel wall subject to bank encroachment is approximately 800 ft, with a
resulting surface area of 8 × 103 sq ft. Based on analysis of temporal changes in
width, the depth-averaged rate of sediment accumulation along the west channel
wall is estimated to be 1.5 ft/year. This intrusion mode converts to an
accumulation rate of 440 cu yd/year on the west channel wall.
Although the annual rate of channel infilling is difficult to quantify (because
the rate produces depth change approaching survey error), a rate of 0.125 ft/year
(1.5 in./year) is considered a reasonable estimate based on the measured channel
elevation changes between May 1980 and October 1989. The surface area of the
Federal navigation channel with the area analyzed is 2.16 × 105 sq ft. The rate of
278 Chapter 6 Inlet Morphology and Stability
sediment accumulation due to channel infilling is thereby estimated to be
100 cu yd/year. This estimate corresponds well to volumes dredged in recent
times. The total rate of shoaling within the study area is estimated to be
1,280 cu yd/year, with the greatest amount of shoaling (1,180 cu yd/year)
occurring along the channel walls.
The total flood shoal volume was estimated with the empirical relation of
Carr de Betts (1999). Because the channel at Mattituck Inlet is constricted
compared to a relatively open bay, and there are no other recognizable areas of
shoaling, the near-field flood shoal volume predicted was considered appropriate.
Applying a tidal prism of 4.32 × 107 cu ft, the total volume of the flood shoal
was calculated to be 4.33 × 105 cu yd, and the total flood shoal area was
calculated to be 5.50 × 106 sq ft.
The empirical relation predicts a value that is larger than the directly
estimated volume by a factor of 10. Four reasons can be given for this large
difference:
a. The tidal current at Mattituck Inlet is weak compared to typical Florida
inlets where Carr de Betts (1999) performed her studies, and weak in
general compared to other permanent inlets. A weaker flood current
implies weaker transport and a smaller flood shoal.
b. The sediment on the beaches adjacent to Mattituck Inlet contains a large
coarse fraction as opposed to the homogeneous fine sand on Florida
beaches. Therefore, a smaller amount of fine material of the total
sediment load is available to be transported to the interior channel at
Mattituck Inlet.
c. Longshore sediment transport rates along the Atlantic coast and Gulf
coast of Florida exceed the estimated transport rates along the north
shore of Long Island by a factor of as much as 10, and 2 to 5 (including
hurricanes), respectively, again indicating less material is brought to the
inlet entrance and available for transport into the inlet.
d. Portions of the flood shoal in and around the navigation channel are
dredged.
Goldsmith Inlet
Similar to the situation of Mattituck Inlet, Goldsmith Inlet is in the low-tide-
dominated inlet classification range according to Davis and Hayes (1984)
(Figure 6-1). In contrast to Mattituck Inlet, Goldsmith Inlet does not fit the
description of a tide-dominated inlet identified by Hubbard et al. (1979). The
morphology of Goldsmith Inlet is more similar to that of a wave-dominated inlet,
having no apparent ebb-tidal shoal and a well-developed flood shoal. Because of
the strong direction of net longshore transport to the east and the coarse sand and
gravel predominant at the site, it is inferred that sediment bypasses the inlet
relatively close to shore, typically within the swash zone.
Table 6-5 lists r-values for Goldsmith Inlet and the quantities entering the
calculation. The surface area of Goldsmith Inlet and Pond was found to be 9.5 ×
105 sq ft interpreted from GIS analysis of an aerial photograph dated 16 April
2003. The spring tidal range within the pond was calculated to be 3.2 ft based on
the water-level data collected 19 September to 8 October 2002. As with
Chapter 6 Inlet Morphology and Stability 279
Mattituck Inlet a range of 15,000 to 25,000 cu/yd year was employed as the gross
transport rate.
Inlets with an r ratio of less than 20 tend to be unstable and non-navigable,
and sand bypassing is accomplished by wave-driven transport across the
bypassing bars. Goldsmith Inlet is non-navigable and does not have an ebb shoal
or bypassing bar, in conformance with the prediction.
Table 6-5
Goldsmith Inlet r Ratio and Associated Physical Quantities
Quantity Goldsmith Inlet
Tidal range (ft) 3.2
Surface area (sq ft) 9.5 × 105
Tidal Prism (cu ft) 3.04 × 106
Transport rate (cu yd) 15,000 - 25,000
r ratio 4.5 – 7.5
Goldsmith Inlet channel cross-sectional area stability
The stability of Goldsmith Inlet was analyzed with the CEA model. Because
Goldsmith Inlet is a small inlet located on a sheltered coast, the predictive
equation derived by Byrne et al. (1980) for small inlets was selected and entered
as a user-specified relation in the model. The minimum cross-sectional area of
the inlets studied by Byrne et al. (1980) ranged from 5.4 to 270 sq ft, bracketing
the minimum cross-sectional area at Goldsmith Inlet of 80 sq ft. The channel
area was obtained from the bathymetry survey of 6-8 October 2002.
Table 6-6 summarizes the physical quantities that served as input to calculate
the equilibrium channel area of Goldsmith Inlet. Cross-section 2 in Figure 3-44a
was selected to represent the minimum cross-sectional area (80 sq ft) for
Goldsmith Inlet. This cross section has a width of 55 ft at this location. Cross
sections were generated based upon a limited number of data points, for which
the perimeter of the inlet was not explicitly recorded. Because the indicated
channel width (55 ft) was considered to be too large based on field observations,
the effective wetted width was taken to be 45 ft.
Table 6-6
Channel Equilibrium Area Information for Goldsmith Inlet
Ocean tide amplitude
(ft) 2.0 Channel length (ft) 1,300
Surface area (sq ft) 9.5 x 105 Channel width (ft) 45
Hydraulic radius (ft) 1.4 Channel area (ft) 80
A tidal range of 4 ft was employed in the stability analysis of Goldsmith Inlet
to compensate for the action of the sill (higher bottom) located at the entrance
and toward the opening into the pond, which limit the tide range in the pond to
3.2 ft. The range of 4 ft is considered an effective range that would exist if the
entrance were not depth limited by the sills.
280 Chapter 6 Inlet Morphology and Stability
Figure 6-7 plots the measured water level and water level as calculated with
the CEA model for Goldsmith Inlet. The CEA model cannot reproduce the
asymmetry of the observed signal (as discussed in Chapter 4). The model can
still give an estimate of stable channel cross-sectional area if the amplitudes
correspond in the calibration.
1200 1200 120024002400
7 October 2002 GMT
Measured
6 October
-4
-3
-2
-1
0
1
Wa
t
e
r
L
e
v
e
l
,
f
t
N
A
V
D
8
8
2
3
4
5 October
Goldsmith Pond Water Level Calculated- - -
___
Figure 6-7. Goldsmith Pond water-level measurements and calculations by
CEA model
Figure 6-8 shows the calculated maximum velocity curve and the calculated
equilibrium velocity curve for Goldsmith Inlet. The empirical relation for small
inlets developed by Byrne et al. (1980) predicts an equilibrium cross-sectional
area of 109 sq ft for Goldsmith Inlet, and their empirical equation with the CEA
Escoffier analysis gives a stable channel cross section of 114 sq ft. These
calculations are close to value of the minimum channel cross-sectional area of
80 sq ft obtained from the October 2002 survey.
Figure 6-9 plots the tidal prism and channel area relation for Goldsmith Inlet
with data of the inlets studied by Byrne et al. (1980) and Simpson (1976). The
Goldsmith Inlet data points conforms well with the trend of the small Chesapeake
Bay inlets. The two Puget Sound inlets studied by Simpson (1976), Lagoon
Point Inlet and Hancock Lake Inlet, are included because they are similar to
Goldsmith Inlet in being small, gravelly inlets. The inlets studied by Simpson
(1976) were not protected by jetties.
Chapter 6 Inlet Morphology and Stability 281
E q u i l i b r i u m
C a l c u l a t e d
114 sq ft
E q u i l i b r i u m
C a l c u l a t e d
114 sq ft
Figure 6-8. Escoffier curve calculated for Goldsmith Inlet, CEA model
100
101
102
103
Ch
a
n
n
e
l
A
r
e
a
,
s
q
f
t
104 105 106 107 108
Tidal Prism, cu ft
Goldsmith Inlet
Chesapeake Bay unjettied inlets
Byrne et al regression equation
Lagoon Point Inlet
Lake Hancock Inlet
Figure 6-9. Tidal prism-channel area relation, Goldsmith Inlet, Chesapeake Bay
small inlets, and Puget Sound inlets
282 Chapter 6 Inlet Morphology and Stability
Similar to the Chesapeake Bay inlets studied by Byrne et al. (1980),
Goldsmith Inlet is small and located on a coast receiving limited longshore
sediment transport. Unlike the Chesapeake Bay inlets, however, Goldsmith Inlet
is protected by one jetty and comprises medium to coarse grain sediment.
Blockage of longshore sediment transport by the Goldsmith Inlet jetty and the
streaming of this material past the inlet mouth as discussed in Chapter 4 would
reduce sediment arrival to the inlet and, therefore, promote a larger channel
cross-sectional area.
For Goldsmith Inlet, the width-to-depth ratio, W/D = 32, based on
measurements listed in Table 6-6. The inlet channel is, therefore, less efficient
than the small Chesapeake Bay inlets studied by Byrne et al. (1980) where the
average W/D = 23. However, as compared to the larger inlets studied by Jarrett
(1976), it is highly hydraulically efficient.
Goldsmith Inlet ebb shoal
Goldsmith Inlet does not posses an ebb shoal, as discussed in Chapter 4.
Instead, a subaqueous spit is present eastward from the jetty, in the direction of
predominant eastward longshore transport. Longevity of the inlet is inferred to
owe in part to eastward migration and orientation of the inlet mouth, enabling
sediment that would otherwise be deposited in the entrance to bypass the inlet.
The bar crossing the mouth of Goldsmith Inlet is morphologically similar to a
spit growing from the large fillet that forms on the east side of the jetty. This
fillet receives sediment that is transported close to shore and around the jetty
from west to east.
A conventional ebb shoal is considered to form and be maintained as a
balance of the ebb current that transports sediment seaward and wave-induced
currents that transport sediment shoreward. For Goldsmith Inlet, the ebb current
is weak as compared to the flood current, and it is doubtful that it can sustain an
appreciable ebb shoal and sweep the channel clear of course sediment if the inlet
were stabilized to enter normal to the shoreline, parallel to the jetty. In addition,
the ebb discharge from Goldsmith Inlet is relatively small compared to the
volume of water moved by obliquely incident waves. Therefore, the ebb flow is
not adequate to maintain an ebb shoal. In migration of the inlet mouth to the
east, the ebb current issuing from the mouth of the inlet will tend to reinforce the
wave-induced longshore current directed to the east. Based on this interpretation,
the most stable configuration of Goldsmith Inlet is one with the channel directed
toward the east, not northward or parallel to the jetty.
Goldsmith Inlet flood shoal
The flood shoal at Goldsmith Inlet consists of three lobes that are located on
the east bank, west bank, and in the channel where the inlet channel enters
Goldsmith Pond (Figure 6-10). The volume of the flood shoal at Goldsmith Inlet
is estimated directly through bathymetry difference calculations in a GIS, after
Dean and Walton (1973) and using the empirical relation derived by Carr de
Betts (1999).
Chapter 6 Inlet Morphology and Stability 283
Because the ambient depth in the eastern portion of Goldsmith Pond is
greater than in the western portion and within the channel, two polygons were
created to estimate the total volume of the flood shoal. One polygon
encompassed the west and channel lobe, and the other encompassed the east lobe.
No area was found that contained a clearly identifiable ambient depth, so the
ambient depth was approximated from depths surveyed adjacent to each polygon.
This depth was multiplied by the surface area of each lobe, yielding the volume
of water located above each idealized “no-shoal” bathymetry.
Figure 6-10. Shoaling at Goldsmith Inlet and Goldsmith Pond, 8 October 2002
A TIN was generated for each polygon and the volume of water located
between each TIN and the NAVD88 datum was calculated. Subtracting the
volume of the water found above each TIN from the value that represented an
ambient water volume yielded an estimate of the volume of each lobe. The
estimated ambient depths for the west lobe and channel lobe are 2.0 ft, and the
estimated ambient depth for the east lobe is 4.5 ft. The volume of the west lobe
was calculated to be 2,915 cu yd and the volume of the west lobe was calculated
to be 3,715 cu yd. Quantities used to determine this estimate are summarized in
Table 6-7.
284 Chapter 6 Inlet Morphology and Stability
Table 6-7
Goldsmith Inlet Flood Shoal and Physical Quantities
Location West and Channel Lobe East Lobe
Ambient depth (ft) 2 4.5
Surface Area (sq ft) 7.86 × 104 3.0 × 104
Estimated volume
above ambient depth
(cu yd) 5,825 5,000
Estimated volume
above shoal (cu yd) 2,910 1,285
Estimated volume of
flood shoal (cu yd) 2,915 3,715
The total flood shoal volume was also estimated with the empirical relation
of Carr de Betts (1999). Because of the small size of Goldsmith Inlet and pond,
the relation that predicts the near field ebb shoal volume was employed, as it is
believed that much of the flood shoal accumulation can be observed. Applying a
tidal prism of 3.04 × 106 cu ft, the total volume of the flood shoal was calculated
to be 1.88 × 105 cu yd and the total flood shoal area was calculated to be 2.80 ×
106 sq ft. The directly calculated volume of both lobes is 6,630 cu yd.
The empirical relation overestimates the volume derived from measurements
by a factor of 30. Reasons for this are the same as presented in the analysis for
Mattituck Inlet.
Discussion of Channel Cross-Sectional Area
Relations
Channel cross-sectional areas of Mattituck Inlet and Goldsmith Inlet are
compared here. To examine the response of cross-sectional areas of small inlets
such as these to tidal forcing, the Jarrett (1976), equation for Atlantic coast dual-
jettied inlets is drawn together with the Byrne et al. (1980) equation for small,
inlets without jetties (Figure 6-11). Data from which the regression equations
were obtained are included in the plots. Measurements for the two Puget Sound
gravelly inlets from Simpson (1976) and for Mattituck Inlet and Goldsmith are
also plotted.
Chapter 6 Inlet Morphology and Stability 285
104 105 106 107 108 109 1010
Tidal Prism, cu ft
100
101
102
103
104
Ch
a
n
n
e
l
A
r
e
a
,
s
q
f
t
105
106
Jarrett regression equation
Mattituck Inlet
Lagoon Point Inlet
Goldsmith Inlet
Atlantic coast dual-jettied Inlets
Chesapeake Bay unjettied inlets
Byrne et al regression equation
Lake Hancock Inlet
Figure 6-11. Comparison of channel cross section and tidal prism relations
The trend lines were extended beyond their empirical ranges of validity for
visual comparison. The trends for the Atlantic coast dual-jetty inlets and the
small natural inlets are different. On Figure 6-11, Mattituck Inlet lies at the
lower end of the Atlantic Coast dual-jetty inlets and close to the regression line.
In contrast, Goldsmith Inlet lies at the upper end of the small Chesapeake Bay
inlets, and it almost falls on top of their regression line. The two small Puget
Sound inlets are also compatible with the small-inlet trend developed from the
Chesapeake Bay inlets.
It appears that the conclusion of Byrne et al. (1980) about the greater
efficiency of small inlets is valid, although it can be argued that the Goldsmith
Inlet and two Puget Sound Inlet data points are compatible with an extension of
the Atlantic coast dual-jetty trend line. However, it is considered that the
location of the Goldsmith Inlet point is accidental in plotting near the Atlantic
coast dual-jetty trend line, as do a few of the Chesapeake Bay data points.
286 Chapter 7 Comparative Analysis and Conclusions
7 Comparative Analysis and
Conclusions
This study of Mattituck Inlet and Goldsmith Inlet, Long Island, NY, covered
the historic and geomorphic background, literature, field measurements,
numerical modeling of tidal circulation, and analysis of inlet morphology.
Information contained in the preceding chapters of this report is comprehensive
and varied. This chapter integrates and synopsizes study results and findings of
the morphologic characteristics of the two inlets for engineering applications.
Recommendations are given to improve the quality of future investigations and
to support coastal and navigation projects located on the north shore of Long
Island.
Tidal inlets on the north shore of Long Island opening to Long Island Sound
have received little study compared to those on the south shore that open to the
Atlantic Ocean. It appears that most inlets on the north shore have been more
stable and in existence longer than the inlets on the south shore. For example, on
the south shore, Fire Island Inlet migrated several miles westward between 1824
and 1940 (Gofseyeff 1952), Moriches Inlet closed for decades in the twentieth
century (Czerniak 1977), and the Great Storm of 1938 reopened Shinnecock Inlet
in the twentieth century. Such extremes have not been reported for inlets located
on the north shore. Inlets on the north shore, therefore, hold value for furthering
understanding of basic inlet processes, in particular, of inlet stability. Knowledge
and insight gained on the mechanisms contributing to the stability of Long Island
north shore inlets will provide information and guidance for maintaining inlets in
general.
Another motivation for the study of inlets along the north shore of Long
Island is the large range in grain size of the sediments on this coast, where both
coarse sand and gravel are present. In contrast, most studies and findings for
inlets concern coasts consisting primarily of uniform fine-to-medium sands.
Mattituck Inlet, with a federally maintained navigable channel, is located
5.2 miles to the west and is larger than Goldsmith Inlet, although small relative to
the six permanent inlets on the south shore of Long Island. Goldsmith Inlet is a
small inlet and the easternmost on the north shore. Goldsmith Inlet has
undergone moderate anthropogenic manipulation as compared to Mattituck Inlet.
Therefore, the two neighboring inlets provide a reasonable range in physical
characteristics to make comparisons and search for controlling variables on inlet
stability and hydrodynamics.
Chapter 7 Comparative Analysis and Conclusions 287
Summary of Inlet Characteristics
Findings of this study on the morphology, sediment, hydrodynamics, and
engineering activities at Mattituck Inlet and Goldsmith Inlet are summarized in
Tables 7-1 to 7-4, respectively. These compilations are discussed in subsequent
sections of this chapter.
Table 7-1
Mattituck Inlet and Goldsmith Inlet – Morphologic
Characteristics
Characteristic Mattituck Inlet Goldsmith Inlet
r ratio 64-107 4.5-7.5
Hydrodynamic dominance Tide dominated (low) Tide dominated (low)
Offshore characteristics Longshore bars west of inlet
Offshore depression on both
sides of inlet
Gross longshore sediment
transport rate estimate
(cu yd/year) 16,000 - 21,000 15,000 - 25,000
Presence of ebb shoal No No
Presence of flood shoal Yes Yes
Bypassing mechanism Probably small to negligible Within swash zone
Channel shoaling mode Bank encroachment Channel infilling
Minimum cross-sectional area
(observed) (sq ft) 1,600 80
Minimum cross- sectional area
(theoretical prediction) (sq ft) 1,020 114
Average depth (ft, mlw) 9 1-2
Channel width-to-depth ratio 43 32
Table 7-2
Mattituck Inlet and Goldsmith Inlet, Nearshore Slopes and
Sediment Grain Size
Characteristic Mattituck Inlet Goldsmith Inlet
Nearshore slope - west of Inlet 1:15 1:10
Nearshore slope - east of Inlet 1:25 1:10
Median grain size - west of Inlet
(mm) 3.15 3.0
Median grain size - east of Inlet
(mm) 0.49 0.49
Median grain size - channel
entrance (class) Coarse sand Coarse gravel
Median grain size -
mid-channel (class) Medium to fine sand Medium to fine gravel
Median grain size - channel
egress (class) Very coarse sand Very coarse to coarse sand
Median grain size - flood shoal (not sampled) Very coarse to coarse sand
288 Chapter 7 Comparative Analysis and Conclusions
Table 7-3
Mattituck Inlet and Goldsmith Inlet - Hydrodynamic
Characteristics
Characteristic Mattituck Inlet Goldsmith Inlet
Tidal prism (cu ft) 4.32 x 107 3.04 x 106
Mean tide range (in creek and
pond) (ft) 5.26 2.15
Spring tide range (in creek and
pond) (ft) 6 2.9
Average ebb tide duration
(min) 373 536
Average flood tide duration
(min) 370 208
Maximum observed tidal
current (m/sec) 0.4 - 0.5 1.3 and rising
Maximum calculated tidal
current in inlet entrance
(m/sec) 0.47 1.43
Table 7-4
Mattituck Inlet and Goldsmith Inlet, Summary of Key Engineering
Activities
Activity Mattituck Inlet Goldsmith Inlet
Jetty construction dates
1906 - 1914 (intermittent)
1937 - 1938 (west jetty seaward extension)
1946 (east jetty landward extension) 1963 - 1964
Jetty length (ft)
1,020 - east jetty
1,320 - west jetty 350-400
Width between jetties (ft) 400 NA
Average volumes dredged
(cu yd)
38,000 (1921 - 1965)
17,000 (1980 - 2004) 4,700
Typical interval between
dredging (years)
4.9 (1921 - 1965)
13 (1980 - 2004 1 - 1.5
Dredging depth (ft) mlw 7 plus 2 3
Comparative Analysis
This section gives an integrated comparative analysis of Mattituck Inlet and
Goldsmith Inlet. Tables 7-1 to 7-4 can be consulted for additional or related
information.
Forcing
Mattituck Inlet and Goldsmith Inlet experience almost the same tidal forcing,
incident waves, wind, storms, and longshore sediment transport potential by
waves. The average and spring tidal ranges in eastern Long Island Sound near
Chapter 7 Comparative Analysis and Conclusions 289
these inlets are 5.2 and 6.0 ft, respectively. Predominant waves are out of the
west, both in height and duration of incidence. Data are lacking on the wave
climatology of Long Island Sound with which to make quantitative predictions
with standard engineering formulas. The long-term net longshore sediment
transport is estimated to be 15,000 cu yd/year to the east at Goldsmith Inlet and
somewhat less at Mattituck Inlet, based upon impoundment rates at the jetties,
the orientation of the inlets relative to the predominant direction of wave
incidence, and consistency with dredging records. Batten and Kraus (2005)
obtained a net rate of 16,000 cu yd/year to the east at Mattituck Inlet and a gross
rate of 21,000 cu yd/year based on a sediment budget analysis.
Both inlets supported tidal mills in the 1700s and 1800s, owing to the
significant tidal range and relatively narrow channels. Therefore, in their natural
states, the inlets must have experienced substantial tidal flow much of the year,
although it is believed that the inlets would close temporarily due to presence of
ice in winter and by occasional blockage from longshore sediment transport.
General features of geomorphology
Mattituck Inlet and Goldsmith Inlet share similar geologic settings
characterized by coarse sediment and steep slopes, a result of the glacial origins
of Long Island and a terminal moraine (Harbor Hill Moraine) located near the
north shore. Each inlet lies at the center of a pocket beach bounded by
headlands, and the adjacent beaches, cliffs, and the neighboring coastal cliffs of
glacial origin are composed of a wide variety of grain sizes. Both inlets and their
back bays are likely low-lying watersheds created by glaciers, and these areas are
prone to sediment deposition.
The predominant grain size on the beaches and in the inlet entrances ranges
between medium sand to gravel. In their natural states, prior to construction of
jetties, the entrances to both inlets probably migrated moderately eastward (order
of tens of feet for Goldsmith Inlet and hundreds of feet for Mattituck Inlet),
returning to their root or original channel locations by breaking through the spit
formed as part of the migration process. Mattituck Creek bends to the west
before interrupting the dune line and exiting to Long Island Sound, suggesting
underlying geologic control (hard bottom) that prevents direct access to the
sound. A large number of glacial erratics can be observed in the nearshore on the
eastern side of Mattituck Inlet. Cross-sectional channel stability of Goldsmith
Inlet may also have been promoted by either a geologic control or structures to
the west of the present location of the inlet.
The area offshore (12-30 ft mlw) of each inlet is composed predominantly of
fine to medium grained sand. The offshore east of each inlet contains higher
percentages of medium grained sand than areas west. No offshore area contains
gravel, with the notable exception of the offshore shoal formation east of
Mattituck Inlet, which has a gravel content estimted at 31 percent. The
distribution of sediment grain sizes for the nearshore area west of both inlets is
bimodal, with large percentages of medium grained sand and gravel. The
nearshore area east of each inlet is composed predominantly of fine and medium
sand. The sediment in the Federal navigation channel at Mattituck Inlet is a
mixture of fine, medium, and coarse sand, and trends toward coarser material
proceeding into the inlet. At Goldsmith Inlet, the inlet entrance is composed
290 Chapter 7 Comparative Analysis and Conclusions
predominantly of gravel and trends towards fine gravel to coarse sand proceeding
south into the inlet. The difference in grain size distribution patterns observed is
attributed to the difference in inlet width. At Mattituck Inlet, wave action has
potential to transport coarse-grained sediment into the inlet. In contrast, the
narrow width at Goldsmith Inlet prevents large waves from entering the inlet.
Coarse-grained sediment is, therefore, not redistributed and remains at the inlet
entrance.
The absence of ebb shoals at Mattituck Inlet and Goldsmith Inlet
distinguishes them from the inlets on the south shore of Long Island (as well as
from other tidal inlets on alluvial coasts), which possess ebb shoals with volumes
in the range of about 8 to 40 million cu yd. Absence of an ebb shoal is a shared
feature with harbors and entrances in the Great Lakes of the United States.
Anthropogenic influences
Although Mattituck Inlet and Goldsmith Inlet have similar forcing and
geologic setting, there are substantial distinguishing physical characteristics.
Two jetties built approximately 100 years ago have been maintained and
improved to support shallow-draft navigation protecting Mattituck Inlet.
Mattituck Inlet has been dredged extensively, possible to as deep as 20 ft mlw in
certain locations of the Federal navigation project by commercial mining
interests. Commercial mining took place on the beach directly west of the west
jetty between 1960 and 1975 (and probably earlier) as well. Combined, it is
estimated that these activities removed an estimated 500,000 to 900,000 cu yd of
sediment from the inlet and littoral system between the 1920s and 1970s.
Material dredged as part of the Federal navigation project prior to the 1946 was
probably placed offshore (and could feasibly have contributed to the volume of
the offshore shoal located east of the inlet), whereas material dredged between
the 1960s and present has been placed on the downdrift beach.
The jetties at Mattituck Inlet are 400 ft apart, and the navigation channel is
100 ft wide at the bottom, maintained to a minimum depth of 7 ft mlw plus 2 ft
allowable overdredging. The width of Goldsmith Inlet varies and is typically on
the order of 25 to 75 ft, depending on the stage of tide. Two jetties fix the
location of Mattituck Inlet, whereas the entrance to Goldsmith Inlet can migrate
to the east, in the direction of net longshore sediment transport induced by
breaking waves. There is geomorphic evidence that the mouth of Mattituck Inlet
migrated west prior to construction of the jetties, but would return to its root
channel, Mattituck Creek. Typical greater depths at Mattituck inlet range
between 7 and 18 ft, mlw, whereas typical greater depths at Goldsmith Inlet
range between 2 and 4 ft mlw.
The jetty at Goldsmith Inlet was constructed 40 years ago (1964) and is not
maintained. The jetty functions as a sediment-retention structure or groin,
serving no navigation purpose. The structure can be termed as a jetty only in
historic context as part of a marina-development plan that was not implemented.
Goldsmith Inlet has been dredged or excavated intermittently and shallowly (to
maximum depth of about 3 ft mlw) in the past half century. Material dredged
from Goldsmith Inlet since the 1970s has been placed on the downdrift beach.
Because the jetty at Goldsmith Inlet has reached impoundment capacity, the inlet
Chapter 7 Comparative Analysis and Conclusions 291
has increasingly returned to a natural condition, where the inlet entrance is
oriented at an acute angle in relation to the shoreline.
Multiple (typically, two or three) longshore bars are prominent to the west of
Mattituck Inlet, but bars are absent west of Goldsmith Inlet, perhaps owing to a
depression in the nearshore located just west of the jetty. Significant longshore
bars are not found along the beaches directly to the east of the inlets. The
shorelines to the west of both inlets have advanced considerably through
impoundment at the west jetties, as compared to the position of the respective
shorelines to the east, which receded after construction of the jetties at both
locations. The shorelines to the west of the inlets are considerably smoother than
the shorelines directly to the east. Material dredged as part of Federal navigation
project channel maintenance prior to the dredging of 1946 was probably placed
offshore. Condition surveys and dredging records indicate that material dredged
in 1946 and later, with the exception of the dredging of 1961, was placed on the
downdrift beach or in the nearshore of the downdrift beach.
Hydrodynamics and tidal shoals
The tidal prism at Mattituck Inlet is about 14 times greater than that at
Goldsmith Inlet. However, the maximum current velocity through the mouth of
Goldsmith Inlet can exceed 1 m/sec, whereas at Mattituck Inlet the current
between the jetties rarely exceeds 0.5 m/sec. Numerical modeling of Mattituck
Inlet in a representative natural condition (nineteenth century) indicated a
maximum current exceeding 1 m/sec, similar to that at Goldsmith Inlet. Despite
the great differences in tidal current, both inlets share geomorphic commonality
in possessing flood shoals composed of fine-to-medium sand, and each lacks an
ebb shoal.
Although the maximum ebb-current velocity at Goldsmith Inlet exceeds
1 m/sec and is comparable to that at other inlets that have formed ebb-tidal
shoals, the volume of water flow or discharge is evidently too small to construct
an ebb shoal. Sediment transported by the ebb current to the mouth of Goldsmith
Inlet is moved away from the entrance by waves and the wave-induced longshore
current.
Strong flood dominance exists at Goldsmith Inlet, which promotes
movement of sediment, particularly fine sand, toward Goldsmith Pond, creating
broad flood shoals. Numerical simulation of tidal hydrodynamics at Mattituck
Inlet with a configuration representative of conditions prior to jetty construction
indicates that this inlet was also flood dominant. Mattituck Inlet and Goldsmith
Inlet cannot support ebb shoals because the ebb current velocity at Mattituck
Inlet is too weak (maximum of 0.5 m/sec), and the discharge at Goldsmith Inlet is
too small.
Channel cross-sectional area stability
The minimum channel cross-sectional area for Goldsmith Inlet agrees with
the empirical prediction for small inlets in Chesapeake Bay (Byrne et al. 1980).
In contrast, the minimum channel cross-sectional area of Mattituck Inlet is about
one-third larger than the empirical prediction for Atlantic coast dual-jetty inlets
292 Chapter 7 Comparative Analysis and Conclusions
on sandy coasts (Jarrett 1976). The unusually large minimum cross-sectional
area of the channel at Mattituck Inlet experiences a weak tidal current. The large
area is attributed to a combination of overdredging of the inlet by commercial
mining, low longshore sediment transport rate, and sediment blockage by the
jetties.
Given their significant differences, it is remarkable that these two inlets have
remained open, with the possible exception of intermittent short closings, for
more than two centuries and likely much longer. The stability of inlets on the
north shore derives in part from a relatively steep inner shore face, presence of
geologic controls such as glacial erratics or hard points on shore, origins of ponds
as low-lying areas created after glaciation, and relatively weak longshore
sediment transport that is about an order of magnitude less than that on the south
shore. However, other factors have entered in controlling stability, in particular,
commercial mining of sediment, such as at Mattituck Inlet.
Mattituck Inlet, Conclusions
Prior to the 1938 extension of the west jetty, Mattituck Inlet experienced
substantial sediment intrusion through shoal development on the west side. The
extension was effective in eliminating this shoaling. Prior to the 280-ft landward
extension of the east jetty in 1946, a breach and spit formation occurred on the
east side of the east jetty. The 1938 seaward extension of the west jetty and the
1946 landward extension of the east jetty have effectively protected Mattituck
Inlet from sediment intrusion, indicating successful modification or tuning of
these coastal structures. The improvements decreased the long-term average-
shoaling rate at Mattituck Inlet from approximately 8,000 cu yd/year to 1,500 to
2,000 cu yd/year.
While the breach was open, sediment was transported into the inlet entrance
to the west and into the navigation channel where the channel turns eastward. At
present, large dunes and a berm abut the east jetty, reducing breach potential.
The presence of accretionary features on the Long Island Sound side of the east
barrier indicates that shoreline position adjacent to the east jetty has become
stable under typical wave conditions. Some cutting into the backside of the east
barrier, adjacent to the east jetty, by the tidal current and, possibly, reflected
waves is observed. This cutting should be monitored so that the integrity of the
barrier near the east jetty is not compromised.
Considerable commercial mining of sand and gravel took place at Mattituck
Inlet from the 1920s to the mid-1970s. The exact volumes of mining are
undocumented, and some records are missing. It is estimated that mining
resulted in the removal of 250,000 to 500,000 cu yd of sediment from between
the jetties and that mining on the beach directly west of the west jetty removed
260,000 to 400,000 cu yd of sediment. Commercial mining permanently
removed mined material from the littoral zone and beaches. Such mining
contributed to maintenance of the navigation channel, and it is hypothesized in
this study that the amount of commercial mining of the inlet channel increased
the channel cross-sectional area beyond that supported by tidal flow. The
channel will not readily return to an equilibrium cross section because of the low
rate of longshore sediment transport at the site and protection of the channel by
the jetties.
Chapter 7 Comparative Analysis and Conclusions 293
Commercial mining by local permit on the beach directly west of Mattituck
Inlet served to prevent the west jetty from reaching impoundment capacity. The
volume of the attachment fillet located there has grown considerably in recent
years (Batten and Kraus 2005). Because mining of the fillet west of the jetty no
longer takes place, the west jetty will eventually reach impoundment capacity.
This occurrence can in turn be expected to substantially increase bypassing and
sediment accumulation within the inlet.
Most dredging conducted today is performed to remove the flood shoal that
forms at the base of the east jetty and along the west bank opposite this flood
shoal. Sediment accumulating on the flood shoal encroaches into the channel as
a steep shoal growing southward. Wave action is inferred to be a significant
contributing mechanism in mobilizing finer sediments for transport by the flood
tidal current. Waves have been observed to enter directly into the inlet to break
on the opposing gravel beach located at the eastward turn in the channel.
Sediment in this area encroaches into the channel as a steep shoal growing
northward. The sediment arriving to this beach is sorted, with gravel and pebbles
left behind and finer sand transported into the channel by tidal currents and
wave-induced currents.
For the past approximately 50 years, Mattituck Inlet has provided a reliable
channel for the shallow-draft navigation it supports, requiring maintenance
dredging approximately every 10 years. Shoaling patterns occurring today are
largely the same as those observed prior to the improvements of 1938 and 1946,
although removed volumes have diminished.
The existence of the modern-day flood shoal can be traced to the behavior of
the spit that formed in 1891 from the east bank, directed to the west. This spit
migrated and reached an equilibrium position around 1980. Because the spit was
subject to littoral forces over this time and is now mostly below water, it can be
considered a flood shoal. The main area of shoaling occurs along the east bank
where Mattituck Inlet empties into Mattituck Creek and the west bank opposite
this location experiences significant shoaling. Shoaling is caused primarily by
sediment brought into the inlet by storms from the northwest quadrant, to which
the inlet is directly exposed. The major form of shoaling at Mattituck Inlet is in
the form of bank encroachment, particularly at the location of the flood shoal.
Wave action, and the production of waves by boats passing through the inlet are
judged to be significant mechanisms for the redistribution of sediment onto the
banks of the Federal navigation channel.
It is concluded that the morphologic feature at Mattituck Inlet that has the
appearance of a relict ebb-tidal shoal is not an ebb shoal. Reasons for this
conclusion are:
a. The shoal experienced minimal growth from 1927 to 2002.
b. The feature is not hydraulically connected to Mattituck Inlet. Numerical
simulations of the tidal circulation for the present condition and
representative natural inlet condition demonstrate that the ebb-tidal
current is too weak to transport sediment to the shoal.
c. The shoal has a large gravel content, making transport to it by a weak
tidal current infeasible.
294 Chapter 7 Comparative Analysis and Conclusions
d. The feature is located too far to the east to be associated with the inlet as
an ebb-tidal shoal.
The origin of the offshore shoal is unknown. It may be a pre-existing geologic
feature, and a portion of it may be the result of dredged material placement
during the new work dredging of Mattituck Inlet.
Goldsmith Inlet, Conclusions
The presence of a tidal mill at Goldsmith Inlet in the eighteenth and
nineteenth centuries indicates stability of the channel and strong tidal flow prior
to the partial modifications of 1963-1964 as part of proposed and later abandoned
marina development. The construction of a jetty on the west side of the entrance
and the new-work dredging (1964) promoted stability of the inlet by interrupting
longshore transport of sediment to the east for approximately 14 years. In 1978,
the jetty at Goldsmith Inlet appears to have reached impoundment capacity.
After impoundment capacity was reached, rates of sediment intrusion into
Goldsmith Inlet increased. An increased sediment supply resulted in dynamic
morphological evolution within Goldsmith Inlet, partially mitigated by dredging,
initially by Suffolk County and later by the Town of Southold. The increased
rates of sediment intrusion resulted in the creation of an attachment fillet or spit
directly east of the inlet, the eventual maturation of the flood shoal, and a
subsequent increase in the rate of channel infilling.
The reestablishment of an effective natural longshore sediment bypassing
system appears to have taken place sometime in the early 1980s, when the
attached fillet east of the jetty reached an areal extent that promotes bypassing.
Partial dredging from 1980 to 2000 apparently mitigated the continued growth
and maturation of this attached fillet, and the eastward migration of the inlet
entrance. The lack of dredging in recent years (in addition to the continued
degradation of the jetty) has allowed for rapid growth of this feature, and
resulting eastward migration of the inlet entrance (2001-2002). Reestablishment
of a natural system of sediment bypassing has occurred, where sediment is
transferred from this attached fillet via a bypassing bar located near the swash
zone and eventually to the beach east of Goldsmith Inlet.
The current through Goldsmith Inlet is strongly flood dominant, controlled in
main part by the shallow sills in the channel. Because sediment transport is
proportional to a power of water velocity, such as the third power, net sediment
transport is directed into Goldsmith Pond. The greater velocity magnitude at the
inlet mouth entrains and transports larger grain sizes. Because the current
velocity magnitude decreases with distance into the inlet, gradational deposition
occurs, with the larger grain size fractions deposited and finer sediments
transported further into the inlet.
Tidal asymmetry of coastal inlets has been well studied (e.g., Boon 1975;
Boon and Byrne 1981; Aubrey and Speer 1985; Speer and Aubrey 1985; Speer
et al. 1991), as recently summarized by Walton (2002). For example, shoaling
channels truncate the lowest portion of the tide, resulting in a longer falling tide
and a weaker ebb current as compared to the flood current. Such a truncation is a
hypsometric effect, the control of water-surface elevation by the bathymetry or
depths. In the case of Goldsmith Inlet, the elevation of the entire inlet entrance is
Chapter 7 Comparative Analysis and Conclusions 295
located near msl. At the lower water levels of ebb tide, the sills at the flood shoal
and shoreline become more effective in retarding flow. In addition, water enters
the fringing marsh of Goldsmith Pond on flood tide more rapidly than when it
exits on ebb. The effective friction of the marsh, creating storage capacity, will
release water slowly as compared to its entrance at flood tide.
The mouth of Goldsmith Inlet appears to be at or near locational equilibrium
if it is oriented to the east. Past dredging practice has realigned the channel
parallel to the jetty. It is hypothesized here that an orientation with the mouth
directed to the east is the optimum for sediment bypassing and maintenance of
inlet stability. The attached fillet to the east, between the jetty and the inlet
mouth, now functions to bypass sediment via transport in the swash zone.
If the accretion fillet to the west were mined substantially, impoundment at
the jetty would reduce the sediment bypassing volume, turning back the
processes in time.
Recommendations for Future Studies
Wave measurements are lacking for the Long Island Sound and are essential
for improving the reliability of coastal studies both for Long Island and
Connecticut. Long-term measurements will allow development of a wave
hindcast needed in engineering design. The USACE, New England District, and
the New York District could share costs and benefits of wave gauging. At
present, the University of Connecticut operates a nondirectional wave gauge in
the middle of Long Island Sound. This gauge could be upgraded to directional
capability for modest cost.
The amount of sediment that may be directed offshore by jetties along the
north shore of Long Island is unknown. Because of the steep nearshore slope and
coarse material, material directed offshore will not return to the beach. Offshore
movement of sediment is an unanswered question, and it may be related to the
observed reduction in required dredging volume at Mattituck Inlet. It was
beyond the scope of this primarily morphologic study to apply a combined wave,
current, and sediment transport model to estimate offshore sediment transport.
Also, wave data are lacking to drive such a model.
It is recommended that sediment sampling be conducted in the offshore area
of jetties to determine sediment texture and, as necessary, high-resolution
bathymetric surveys be made to detect sediment buildup offshore. These might
be done in conjunction with channel condition surveys.
The rate of channel infilling at Mattituck Inlet is low as compared to early in
the twentieth century, indicating efficient protection by the jetties in their present
configuration. Maintenance dredging removes the portion of the flood shoal that
encroaches upon the Federal navigation channel. This formation has never been
dredged in its entirety. Full removal of the portion of this shoal lying outside the
navigation channel would greatly reduce shoaling at Mattituck Inlet and increase
the required time interval between maintenance dredging, while supplying
material to the downdrift beach. The volume of material that could be provided
is estimated to be on the order of 15,000 cu yd, comparable to that removed from
the channel during the typical 10-year dredging cycle. This feature appears to
function as a groin in accumulating sediment, promoting channel bank
296 Chapter 7 Comparative Analysis and Conclusions
encroachment. Removal of this feature would increase the transport capacity of
the flood current and promote tidal circulation in the neighboring marshes.
Numerical modeling of tidal circulation at Mattituck Inlet in a representative
natural condition revealed marked hydrodynamic similarity to Goldsmith Inlet,
which has a cross-sectional area relation with tidal prism similar to that of small
inlets in Chesapeake Bay. A hypothesis is suggested – that the inlets along the
north shore of Long Island display a unique relation between cross-sectional area
and tidal prism. A regional characteristic relation is plausible given the low rates
of longshore sediment transport, large sediment size, and relatively large tidal
prism found in this region. The tide range within Long Island Sound increases
from east to west. An increase in tidal ranges suggests that inlets along Long
Island Sound will be increasingly stable proceeding east to west. It is further
expected that other north shore inlets in Long Island Sound will lack an ebb shoal
or have a much smaller ebb shoal as compared to the standard predictive formula.
Flood shoals would be large for the shallower inlets.
References 297
References
Allee King Rosen and Fleming, Inc., Moffat and Nichols, Engineers, and The
Saratoga Associates. (1995, revised 1996). “Town of Southold erosion
management plan,” prepared for the Town of Southold, revised by the New
York Department of State, Division of Coastal Resources, and the Town of
Southold.
Alpine Ocean Seismic Survey, Inc. (1998). “Final report on the geophysical
investigation, Duck Pond Point to Horton Point, Southold project,” prepared
for the Town of Southold.
Amein, M., and Kraus, N. C. (1991). “DYNLET1: Dynamic implicit numerical
model of one-dimensional tidal flow through inlets,” Technical Report
CERC 91-10, U.S. Army Engineer Waterways Experiment Station,
Vicksburg, MS.
Aubrey, D. G., and Speer, P. E. (1985). “A study of non-linear tidal propagation
in shallow inlet/estuarine systems, Part I: Observations,” Estuarine, Coastal
and Shelf Science 21, 185-205.
Batten, B. K., and Kraus, N. C. (2005). “Evaluation of shore erosion downdrift
of Mattituck Inlet, New York: Section 111 study,” Technical Report
ERDC/CHL TR-04-xx, U.S. Army Engineer Research and Development
Center, Vicksburg, MS.
Bokuniewicz, H., and Tanski, J. J. (1983). “Sediment partitioning at an eroding
coastal bluff, ” Northeastern Geology 5(2), 73-81.
Boon, J. D., III. (1975). “Tidal discharge asymmetry in a salt marsh drainage
system,” Limnology and Oceanography 20(1), 71-80.
Boon, J. D., III, and Byrne, R. J. (1981). “On basin hypsometry and the
morphodynamic response of coastal inlet systems,” Marine Geology 40, 27-
48.
Bruun, P., and Gerritsen, F. (1959). “Natural by-passing of sand at coastal
inlets,” Journal of the Waterways and Harbors Division 85(WW4),
American Society of Civil Engineers (ASCE), 75-107.
Bruun, P., and Gerritsen, F. (1960). “Stability of tidal inlets.” North Holland
Publishing Co., Amsterdam, 123 p.
Byrne R. J., Gammisch, R. A., and Thomas, G. R. (1980). “Tidal prism-inlet
area relations for small tidal inlets,” Proceedings 17th Coastal Engineering
Conference III, ASCE, 2,517-2,531.
298 References
Carr de Betts, E. E. (1999). “An examination of flood tidal deltas at Florida’s
tidal inlets,” M.S. thesis, Coastal and Oceanographic Engineering
Department, University of Florida, Gainesville, FL.
Comes, C. R. (1954). “Peconic’s Old Gristmill,” Long Island Forum 107.
Cooke, T. W. (1985). “Sediment budget of Stony Brook Harbor, Long Island,
New York,” M.S. thesis, State University of New York at Stony Brook,
Stony Brook, NY, 120 p.
Craven, C .E. (1906). A history of Mattituck, LI, NY. (Reprinted 1988),
Jedediah Clauss and Sons, Amereon Ltd., Mattituck, New York, 11952-9500.
Czerniak, M. T. (1977). “Inlet interaction and stability theory verification,”
Proceedings Coastal Sediments ’77, ASCE, 754-773.
Davies, D. S. (1972). “Stability of the North Shore of Long Island,” Marine
Environmental Studies, State University of New York at Stony Brook.
Davies, D. S., Axelrod, E. W., and O’Connor, J. S. (1971). “Erosion of the north
shore of Long Island,” Technical Report No. 18, State University of New
York, Marine Science Research Center, 101.
Davis, Jr., R. A., and Hayes, M. O. (1984). “What is a wave dominated coast?,”
Marine Geology 60, 313-329.
Dean, R. G., and Walton, T. L. (1973). “Sediment transport processes in the
vicinity of inlets with special reference to sand trapping,” Estuarine Research
II, L. E. Cronin, ed., Academic Press, 129-149.
Escoffier, F. F. (1940). “The stability of tidal inlets,” Shore and Beach 8(4),
114-115.
Fields, L., Bosma, K. F., and Byrnes, M. R. (1999). “Historical shoreline
change analysis: Western town line to Horton Point, Southold, NY, final
report,” Aubrey Consulting, Inc., East Falmouth, MA.
FitzGerald, D. M. (1988). “Shoreline erosional-depositional processes
associated with tidal inlets,” Hydrodynamics and Sediment Dynamics of
Tidal Inlets, D. G. Aubrey, and L. Weishar, eds., Springer, Berlin, 186-225.
FitzGerald, D. M., Kraus, N. C., and Hands, E. B. (2000). “Natural mechanisms
of sediment bypassing at tidal inlets,” ERDC/CHETN-IV-30, U.S. Army
Engineer Research and Development Center, Vicksburg, MS.
Fuller, M. L. (1914). “The geology of Long Island, New York,” U.S. Geological
Survey Professional Paper 82, 231 p.
Gaudiano, D. J., and Kana, T. W. (2000). “Shoal bypassing in South Carolina
tidal inlets: Geomorphic variables and nine empirical predictions for nine
mesoscale inlets,” Journal of Coastal Research 17(2), 280-291.
Gofseyeff, S. (1952). “Case history of Fire Island Inlet, NY.” Proceedings of
Third Conference on Coastal Engineering, Council on Wave Research, 272-
305.
Goodwin, P. (1996). “Predicting the stability of tidal inlets for wetland and
estuary management,” Journal of Coastal Research 81(23), 83-101.
References 299
Greenman-Pedersen Associates, P.C. (1981). “Report on the shoreline impacts
of the Goldsmith Inlet jetty,” in Town of Southold (2003), “local waterfront
revitalization program,” prepared by V. Scopaz, AICP Town Planner with
assistance from S. Ridler, Coastal Resources Specialist, New York State
Department of State Division of Coastal Resources.
Hayes. M. O. (1977). “Barrier island morphology as a function of tide and wave
regime,” Proceedings Coastal Symposium on Barrier Islands,
S. Leatherman, ed., Academic Press, New York, 1-27.
Hayes, M. O. (1980). “General morphology and sediment patterns in tidal
inlets,” Sedimentary Geology 26, 139-156.
Hubbard, D. K., Oertel, G., and Nummedal, D. (1979). “The role of waves and
tidal currents in the development of tidal-inlet sediment structures and sand
body geometry; examples from North Carolina, South Carolina, and
Georgia,” Journal of Sedimentary Petrology 49(4), 1,072-1,092.
Hughes, S. A. (2002). “Equilibrium cross sectional area at tidal inlets,” Journal
of Coastal Research 19(1), 160-174.
Hume, T. M., and Herdendorf, C. E. (1990). “Morphologic and hydrologic
characteristics of tidal inlets on a headland dominated, low littoral drift coast,
northeastern New Zealand,” Proceedings Skagen Symposium, Journal of
Coastal Research SI 9, 527-563.
Jarrett, J. T. (1976). “Tidal prism-inlet area relationships,” GITI Report 3, U.S.
Army Engineer Waterways Experiment Station, Vicksburg, MS.
Johnson, D. W. (1919). Shore processes and shoreline development. John
Wiley and Sons, Inc., London.
Kana, T. W. (1995). “A mesoscale sediment budget for Long Island, New
York,” Marine Geology 126, 87-110.
Koppelman, L. E., Weyl, P. K., Gross, M. G., and Davies, D. S. (1976). The
urban sea - Long Island Sound. Praeger Publishers, New York, 223.
Kraus, N. C. (1998). “Inlet cross-sectional area calculated by process-based
model,” Proceedings 26th Coastal Engineering Conference, ASCE, 3,265-
3,278.
Kraus, N. C. (2000). “Reservoir model of ebb-tidal shoal evolution and sand-
bypassing,” Journal of Waterway, Port, Coastal, and Ocean Engineering
126(6), 305-313.
Kraus, N. C., and Rosati, J. D. (1997). “Interpretation of shoreline-position data
for coastal engineering analysis,” Coastal Engineering Technical Note
CETN-II-39, U.S. Army Engineer Waterways Experiment Station,
Vicksburg, MS.
Kraus, N. C., and Rosati, J. D. (1998). “Estimation of uncertainty in coastal-
sediment budgets at inlets,” Coastal Engineering Technical Note CETN-IV-
16, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS.
300 References
Kraus, N. C., Zarillo, G. A., and Tavolaro, J. F. (2003). “Hypothetical relocation
of Fire Island Inlet, New York,” Proceedings Coastal Sediments ’03, CD-
ROM published by World Scientific Press and East Meets West Productions,
Corpus Christi, TX, ISBN-981-238-422-7, 14 p.
Kumar, N., and Sanders, J. E. (1974). “Geomorphic and stratigraphic analysis of
Fire Island, New York, Marine Geology 21, 491-532.
Leatherman, S. P. (1989). “Role of inlets in geomorphic evolution of the south
shore of Long Island, N.Y., USA,” Environmental Management 13, 109-115.
Leatherman, S. P., and Allen, J. R., eds. (1985). “Geomorphologic analysis of
south shore of Long Island barriers, New York,” Report to U.S. Army
Engineer District, New York.
Leatherman, S. P., Dean, R. G., Kana, T., and Anders, F. J. (1997). “Goldsmith
Inlet and adjacent areas, north shore of Long Island, New York: Erosion
problems and suggested modifications,” Shore and Beach 65(3), 13-16.
LeConte, L. J. (1905). “Discussion on river and harbor outlets, notes on the
improvement of river and harbor outlets in the United States,” Paper No.
1009, by D. A. Watts, Transactions American Society of Civil Engineers,
306-308.
Luettich, R. A., Jr., Westerink, J. J., and Scheffner, N. W. (1992). “ADCIRC:
An advanced three-dimensional circulation model for shelves coasts and
estuaries, Report 1: Theory and methodology of ADCIRC-2DDI and
ADCIRC-3DL,” Dredging Research Program Technical Report DRP-92-6,
U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS, 137 p.
Lyles, S. D., Hickman, L. E., and Debaugh, H. A. (1988). “Sea level variations
for the United States 1855 – 1986,” National Oceanic and Atmospheric
Administration, National Ocean Service, Rockville, MD, 182 p.
Militello, A., and Kraus, N.C. (2001). “Shinnecock Inlet, New York, site
investigation, Report 4: Evaluation of flood and ebb shoal sediment source
alternatives for the west of Shinnecock Interim Project, New York,”
Technical Report CHL TR-98-32, Coastal Inlets Research Program, U.S.
Army Research and Development Center, Vicksburg, MS.
Militello, A., Kraus, N. C., and Brown, M. E. (2000). “Regional coastal and
inlet circulation modeling with application to Long Island, New York,”
Proceedings of the 13th Annual National Conference on Beach Preservation
Technology, FSBPA, Tallahassee, FL, 191-201.
Moody, J. A. (1988). “Small-scale inlets as tidal filters,” Lecture notes on
coastal and estuarine studies, D. G. Aubrey and L. Weisher, eds., Springer-
Verlag New York, Inc., 137-154.
Morang, A., Rahoy, D. S., and Grosskopf, W. G. (1999). “Regional geologic
characteristics along the south shore of Long Island, New York,”
Proceedings Coastal Sediments ’99, ASCE, 1,568-1,583.
O’Brien, M. P. (1931). “Estuary tidal prisms related to entrance areas,” Civil
Engineering 1(8), 738-739.
O’Brien, M. P. (1966). “Equilibrium flow areas of tidal inlets on sandy coasts,”
Proceedings 10th Coastal Engineering Conference 1, 676-686.
References 301
O’Brien, M. P. (1969). “Equilibrium flow areas of inlets on sandy coasts,”
Journal of Waterways, Ports, and Harbors Division 95(WW1), 43-52.
Offshore and Coastal Technologies, Inc. (1998). “Shoreline monitoring;
Southold town line to Horton Point,” 500 Spencer Road Avondale, PA.
Omholt, F. L. (1974). “Effects of small groins on shoreline changes on the north
shore of Suffolk County, New York,” New York Ocean Science Laboratory
Technical Report No. 0028, Montauk, NY.
Panuzio, T. (1968). “The Atlantic coast of Long Island,” Proceedings 11th
Coastal Engineering Conference, ASCE Press, 1,222-1,241.
Park, M. J. (1985). “Prediction of tidal hydraulics and sediment transport
patterns in Stony Brook Harbor,” M.S. thesis, State University of New York
at Stony Brook, Stony Brook, NY, 146 p.
Ralston, R. R., U.S. Engineer Office, First District. (1928). “Report on survey
of Mattituck Harbor, NY,” in House of Representatives (1935) report from
the Chief of Engineers on preliminary examination and survey of Mattituck
Harbor, NY, House Document No. 8, 71st Congress, 1st Session, U.S.
Government Printing Office, Washington, DC.
Schubel, E. J. (1976). “An assessment of the effects of the periodic removal of
sand from the western jetty at Mattituck Inlet on shore erosion of contiguous
shoreline segments,” Marine Sciences Research Center, State University of
New York, Stony Brook, NY.
Schmeltz, E. J., Sorensen, R. M., McCarthy, J. J., and Nersesian, G. (1982).
Breach/inlet interaction at Moriches Inlet, Proceedings 18th Coastal
Engineering Conference, ASCE, 1,062-1,077.
Schwaab, W. C., Thieler, E. R., Allen, J. S., Foster, D. S., Swift, B. A., Denny,
J. F., and Danforth, W. W. (1999). “Geologic mapping of the nearshore area
offshore Fire Island, New York,” Proceedings Coastal Sediments ’99, ASCE,
1,552-1,567.
Seabergh, W. C. (2003). “Long-term coastal inlet channel area stability,”
Proceedings Coastal Sediments ‘03, CD-ROM published by World Scientific
Publishing Corporation, and East Meets West Productions, ISBN 981-238-
422.7.
Seabergh, W. C., and Kraus, N. C. (1997). “PC program for coastal inlet
stability analysis using Escoffier method,” Coastal Engineering Technical
Note CETN-IV-11, Coastal Engineering Rearch Center, U.S. Army Engineer
Waterways Experiment Station, Vicksburg, MS.
Shepard, F.P. (1963). Submarine geology. Harper and Rowe Publishers, New
York, 557 p.
Signell, R. S., List, J. H., and Farris, A. S. (2000). “Bottom currents and
sediment transport in Long Island Sound: A modeling study,” Journal of
Coastal Research 16(3), 551-566.
Simpson, D. P. (1976). “Hydraulics of two small gravelly tidal inlets,” M.S.
thesis, University of Washington, Seattle, WA, 137 p.
302 References
Smith, E. R. (1988). “Case histories of Corps breakwaters and jetty structures,
Report 5, North Atlantic Division,” Technical Report REMR-CO-3, U.S.
Army Engineer Waterways Experiment Station, Vicksburg, MS.
Speer, P. E., and Aubrey, D. G. (1985). “A study of non-linear tidal propagation
in shallow inlet/estuarine systems, Part II: Theory,” Estuarine, Coastal and
Shelf Science 21, 207-224.
Speer, P. E., Aubrey, D. G., and Friedrichs, C. T. (1991). “Nonlinear
hydrodynamics of shallow tidal inlet/bay systems,” in Tidal Hydrodynamics,
B. B. Parker, ed., Wiley, NY, 321-340.
Taney, N. E. (1961). “Geomorphology of the south shore of Long Island, New
York,” TM No. 128, U.S. Army Corps of Engineers, Beach Erosion Board,
Washington, DC.
Tanski, J., Bokuniewicz, H. J., and Schubert, C. E. (1990). “An overview and
assessment of the coastal processes data base for the south shore of Long
Island, Proceedings of Workshop Held April 10-21, 1989, New York Sea
Grant Program Special Report No. 104, New York State Sea Grant, Stony
Brook, NY.
Tetra Tech, Inc. (1979). “Jamesport nuclear project shoreline study,” Tetra
Tech, Inc. Jacksonville, FL.
Town of Southold. (2003). “Local waterfront revitalization program,” prepared
by Valerie Scopaz, AICP Town Planner, with assistance from Steve Ridler,
Coastal Resources Specialist, New York State Department of State Division
of Coastal Resources.
U.S. Army Engineer District, New York. (1963) “NYSPW beach protection
project 192,” permit granted to the Department of Public Works, State of
New York, NY.
U.S. Army Engineer District, New York. (undated). “Mattituck Harbor dredging
history, 1921 - Present,” New York, NY.
U.S. Army Engineer District, New York. (1969). “North Shore of Long Island
Suffolk County, New York, beach erosion control and interim hurricane
study (survey),” New York, NY.
U.S. Army Engineer District, New York. (2003). “Fact sheet - Mattituck
Harbor, NY,” New York, NY.
U.S. Engineers Office, First District. (1928). “Report on survey of Mattituck
Harbor, NY,” in House of Representatives (1935) “Report from the Chief of
Engineers on preliminary examination and survey of Mattituck Harbor, NY,”
House Document No.8, 71st Congress, 1st Session, U.S. Government Printing
Office, Washington, DC.
U.S. Environmental Protection Agency, and U.S. Army Corp of Engineers.
(2001). “Physical oceanographic evaluation of Long Island Sound and Block
Island Sound.”
Walton, T. L., Jr. (2002). “Tidal velocity asymmetry at inlets,” Coastal
Engineering Technical Note ERDC/CHL CHETN IV-47, U.S. Army
Engineer Research and Development Center, Vicksburg, MS.
References 303
Walton, T. L., and Adams, W. D. (1976). “Capacity of inlet outer bars to store
sand,” Proceedings 15th Coastal Engineering Conference, ASCE, 1,919-
1,937.
Williams, S. J. (1981). “Sand resources and geological character of Long Island
Sound,” Technical Paper No. 81-3, Department of the Army, Coastal
Engineering Research Center, Fort Belvoir, VA, 65 p.
Zarillo, G., and Park, M. (1987). “Sediment transport prediction in a tidal inlet
using a numerical model - application to Stony Brook Harbor, Long Island,
New York, USA,” Journal of Coastal Research 3(4), 429-444.
REPORT DOCUMENTATION PAGE Form Approved
OMB No. 0704-0188
Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining
the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for
reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington,
VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not
display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.
1. REPORT DATE (DD-MM-YYYY)
July 2005
2. REPORT TYPE
Final report
3. DATES COVERED (From - To)
5a. CONTRACT NUMBER
5b. GRANT NUMBER
4. TITLE AND SUBTITLE
Geomorphic Analysis of Mattituck Inlet and Goldsmith Inlet, Long Island,
New York
5c. PROGRAM ELEMENT NUMBER
5d. PROJECT NUMBER
5e. TASK NUMBER
6. AUTHOR(S)
Michael J. Morgan, Nicholas C. Kraus, Jodi M. McDonald
5f. WORK UNIT NUMBER
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT
NUMBER
City University of New York, Hunter College, Department of Geography, 695 Park Avenue,
New York, NY 10021;
U.S. Army Engineer Research and Development Center. Coastal and Hydraulics Laboratory,
3909 Halls Ferry Road, Vicksburg, MS 39180-6199;
U.S. Army Engineer District, New York, 26 Federal Plaza, New York, NY 10278-0090
ERDC/CHL TR-05-2
9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S)
11. SPONSOR/MONITOR’S REPORT
NUMBER(S)
U.S. Army Corps of Engineers
Washington, DC 20314-1000
12. DISTRIBUTION / AVAILABILITY STATEMENT
Approved for public release; distribution is unlimited.
13. SUPPLEMENTARY NOTES
14. ABSTRACT
This study of Mattituck Inlet and Goldsmith Inlet, Long Island, NY, covers the historic and geomorphic background, literature, field
measurements, numerical modeling of tidal circulation, and analysis of inlet morphologic properties. The inlets are located 8.2 km apart
on the eastern end of the north shore of Long Island, NY, facing Long Island Sound. Mattituck Inlet has a federally maintained channel
and dual jetties, and it connects the sound to Mattituck Creek. Mattituck Inlet is the only major harbor on the north fork of Long Island
and is a commercial and recreational boating center. The navigation channel is maintained to a depth of 7 ft mean low water with a 2-ft
allowable overdraft. Goldsmith Inlet connects the sound to Goldsmith Pond. The inlet has a nonfunctional jetty on its west side and is
non-navigable, with typical depths ranging from 0.5 to 3 ft.
Tidal inlets on the north shore of Long Island have received little study compared to those on the south shore that open to the Atlantic
Ocean. It appears that most inlets on the north shore have been more stable and in existence longer than the inlets on the south shore.
Inlets on the north shore, therefore, hold value for further understanding of basic inlet processes, in particular, of channel cross section
and locational stability. Another motivation for the study of inlets along the north shore of Long Island is the large range in grain size of
the sediments on this coast.
(Continued)
15. SUBJECT TERMS
ADCIRC Model
Coastal inlets
Geomorphology
Hydrodynamic modeling
Inlet stability
16. SECURITY CLASSIFICATION OF: 17. LIMITATION
OF ABSTRACT
18. NUMBER
OF PAGES
19a. NAME OF RESPONSIBLE
PERSON
a. REPORT
UNCLASSIFIED
b. ABSTRACT
UNCLASSIFIED
c. THIS PAGE
UNCLASSIFIED 332
19b. TELEPHONE NUMBER (include
area code)
Standard Form 298 (Rev. 8-98)
Prescribed by ANSI Std. 239.18
14. ABSTRACT (Concluded)
Given their significant differences, it is remarkable that Mattituck Inlet and Goldsmith Inlet have remained open
for more than two centuries and likely much longer. The stability of inlets on the north shore derives in part from a
relatively steep inner shore face, presence of geologic controls such as glacial erratics or hard points on shore,
origins of ponds as low-lying areas created after glaciation, and relatively weak longshore sediment transport that is
about an order of magnitude less than that on the south shore of Long Island. However, other factors enter in
controlling stability, in particular, commercial mining of sediment, such as at Mattituck Inlet.