HomeMy WebLinkAboutCoastal Erosion Reconnaisance StudyTOWN OF SOUTHOLD
COASTAL EROSION RECONNAISANCE STUDY
FLOOD PROTECTION BUREAU
N.Y.S. Department of Environmental Conservation
May, 1987
II.
III.
IV.
V.
VI.
Introduction
Scope of Study
Alternatives
Cost Sharing
Conclusion
Recommendations
TABLE OF CONTENTS
Pa~e
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3
4
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LIST OF FIGURES
Study Locations
COASTAL EROSION RECONNAISANCE STUDY
May, 1987
Introduction
A)
Local Request - A coastal erosion study was requested by the
Town of Southold, Suffolk County. Supervisor Francis J.
Murphy, on behalf of the Town, made a for~nal request for
such a study in a January 6, 1987 letter. The letter was in
direct response to a Town Resolution adopted on December 2,
1986.
B)
Authority - The Department of Environmental Conservation is
authorized under Chapter 7, Section 1531 of the
Unconsolidated L~ws to "...arrest erosion and alleviate or
prevent damage resulting therefrom and as protection from
storms..." by construction of "...bulkheads, groins,
Jetties, fills and other works and improvements upon lands
and lands under water owned by any county, city, town,
village, park, or beach erosion control district...".
c)_
Study Location - The study area stretches from Duck Pond
Point to Horton Point on Long Island Sound in the Town of
Southold. The study reach is approximately 5.1 miles long.
Figure 1 shows the study area and its relative location on
Long Island.
II. Scope of Study
A)
Purpose - The purpose of this study is to identify erosion
problems along a reach of Long Island Sound shoreline in the
Town of Southold (Duck Pond Point to Horton Point) and to
determine the feasibility of providing erosion protection
for the area, based on economic, social, environmental, and
engineering considerations.
B)
Initial Investigation and Past History - The area of concern
can be further subdivided into five (5) separate geographic
reaches. They are as follows:
1) Duck Pond Point
2) Goldsmith Inlet
3) Bittner Groin
4) Kenneys Beach
5) Horton Point
The following is a brief description of each reach:
1)
Duck Pond Point - Fairly high bluffs (30-40 feet high) are
extremely vulnerable to high wave energy attacking the toe
of the bluff. Erosion has been so severe in the past that
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STUDY LOC^TIOhl
3)
5)
most of the privately owned property is protected by wooden
bulkheads. The U.S. Army, Corps of Engineers, in a 1969
Survey Report of Long Island's North Shore, indicates that
the shoreline from Oregon Hills, just east of Duck~nd
Point, to Goldsmith Inlet had receded from 100 to 400 feet
over the 130 year period from 1836 through 1965. Based on
that data the shoreline at Duck Pond Point retreated at an
average rate of 3 feet per year.
Goldsmith Inlet - The Goldsmith jetty, constructed in 1964
with a length of some 310 feet, appears to be responsible
for much of the removal of sediment from the eastward
littoral drift. The net effect has been an increase in
beach width west of the Jetty while there has been
significant erosion east of the inlet.
In recent years sediment has begun to bypass the jetty as
the area of accretion on the western side has reached an
apparent state of saturation. However, there has not been a
noticeable increase of deposition of littoral material to
the east of the Jetty and it may be many years, if ever,
before that occurs.
Bittner Groin - The same basic conditions exist in the
vicinity of the Bittner Groin as at Goldsmith Inlet. The
problem, however, is less severe due to the groin's shorter
length(approximately 190 feet long)and the absence of inlet
dynamics. Once again, the groin appears to be the likely
cause of the beach build-up to its west and consequential
beach starvation for a short distance immediately to its
east.
Kenneys Beach - This has been a troublesome spot over the
years. Various attempts to arrest erosion have had only
limited success. Beach nourishment, rubble placement, ~nd
bulkhead construction have had little success in stabilizing
the beach. The erosion problem appears to be getting worse,
particularly in the vicinity of the Town Beach parking lot
and the shoreline immediately to the east. Private effortm
to stabilize the area immediately west of the Town Beach
parking lot have been somewhat successful. Bulkheads, both
steel and timber, a concrete seawall, and low profile
aluminum groins have prevented the degree of destruction
that the parking lot has suffered. However, this success
has been limited by a loss of beach in front of the
bulkheads.
Horton Point - This area resembles Duck Pond Point except
that the bluffs are slightly higher and steeper. The bluffs
have little or no toe protection and are vulnerable to wave
attack. The U.S. Army, Corps of Engineers, in the 1969
Survey Report of the North Shore, indicates that the
shoreline receded 150 feet over the 130 year period from
1836 to 1965. This represents a 1.2 foot average annual
recession rate.
III. Alternatives
A)
Structural - Appropriate solutions to be considered should
include beach nourishment, relocation of threatened homes,
beach stabilization measures such as groins, and
construction of revetments and bulkheads. Care must be
exercised when considering revetments and bulkheads to guard
against exacerbated erosion to adjacent properties and
eventual loss of the beach. In those cases where homes are
in imminent danger of being damaged or destroyed,
consideration should be given to relocating structures
further landward if lot size permits. Whenever possible
this is the preferred solution and for individual property
owners is generally the least costly.
Extreme care and~sound engineering design must be used
when selecting groins and jetties as a solution. The
histories of the Goldsmith Inlet jetty and the Bittner groin
illustrate that such structures may disrupt the littoral
drift, thereby exacerbating erosion downdrift of the
structures. Provisions must be included in any groin
proposal to address the problems of downdrift sand
starvation.
Other possible alternatives should consider shortening of
the jetty at Goldsmith Inlet and removal of the Bittner
groin and combinations of these. To evaluate the overall
effect of these alternatives it is necessary to quantify the
net littoral drift in the immediate vicinity.
To summarize, the following structural alternatives should be
addressed:
1) Groins
2) Beach nourishment
3) Revetments and/or bulkheads
4) Relocation of homes
5) Shortening the Goldsmith Inlet jetty
6) Shortening and/or removing the Bittner groin
Non-Structural - Since the area is not yet fully developed,
it is important to consider non-structural alternatives for
future development. Non-structural measures would not
attempt to reduce flooding or erosion but rather would
regulate the use and development of the area to minimize
erosion losses. Setbacks and development restrictions
could be implemented which would guard against unwise
activities in these-flood and erosion prone areas. The Town
of Southold should consider utilizing Coastal Erosion
Hazard Area Regulations and Flood Plain Management
techniques to minimize future damages. It is obvious from a
review of existing development that many homes have been
built too close to Long Island Sound. Many previous
development activities have destroyed the natural protective
features such as dunes, bluffs, and beaches that protected
this shoreline. It is important not to repeat these
mistakes.
c)
Structural and Non-Structural - In some instances certain
structural measures coupled with appropriate setback
requirements may be the solution. Such solutions would be
site specific and should be addressed accordingly.
IV. Cost Sharin~
Ve
VI.
A)
State-Local - Section 1532 of the Statute specifies a 70%
state and 30% local cost share. The Town of Southold would
be required to enter into an agreement with the State
whereby it would agree to reimburse the State 30% of the
cost of honstruction. The cost of preparing plans,
specifications, c6st estimates, engineering, and inspection
services are considered to be a part of the cost of
construction.
B) Federal-State-Local - In the event that federal monies are
made available for a beach erosion control project the cost
sharing would most likely be 50% federal and 50%
non-federal. The 50% non-federal portion would be broken
- -down to 70% State and 30% local. The local share would
therefore represent 15% and the state share 35% of the
entire cost of construction.
Conclusion
There is sufficient evidence of erosion damage to the studied
reach of shoreline, as well as a number of possible solugions,
to justify a feasibility study. A detailed study would document
historical erosion problems and identify and analyze possible
structural and non-structural solutions. This study should also
include cost and design information for recommended solutions for
publicly owned lands and recommended strategies for the
protection of private lands.
Recommendations
Since the Department does not have the staff resources to prepare
such a study, it is recommended that a consultant be hired. Upon
request from the Town of Southold and assurances that the Town
will reimburse the State for 30% of study costs, the Department
will prepare a budget request fbr the necessary funds and upon
receipt of approval of those funds will prepare a detailed
Request For Proposal (RFP). The study is estimated to cost up to
$50,000 and would determine the feasibility of reducing or
arresting erosion through the construction of erosion protection
structures and/or other appropriate measures.
CEHA/CE7