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HomeMy WebLinkAboutLWRP Sound Shore Erosion Reach 3-Local Waterfront 1995David S. Corwin 639 Main Street Greenport, NY 11944 March 1, 1995 The Honorable Ruth Oliva Town of Southold Main Road Southold, NY Subject: Waterfront Revitalization Erosion Study Dear Ruth: Enclosed please find a brief narrative, photographs and maps relating to the Waferfront Revitalization Erosion Study, reach 3. Also enclosed is a time sheet for January and February, 1995. If you have any questions or ifI can be of further assistance in the Waterfront Revitalization Study please contact me. /~~ry truly/~ours, David S. Corwin Southold Town Local Waterfront Revitalization Study Long Island Sound Shore Erosion Reach 3 February 1995 Submitted By: David S. Corwin, P.E. Reach 3 Table of Contents Text ..................................................................... 1-4 Photographs ....................................................... 5-28 Map East Section ................................................ 29 Map West Section ................................................ 30 Reach 3 GEOMORPHOLOGY Reach 3 is typical of Southold Town's north shore with bluffs as high as 60 feet to areas with no bluff at all such as Southold Town Beach and Inlet Point. The bluffs between Horton's Point and Southold Town Beach are notable because of their high clay content as compared to the typical loamy sand found in most bluffs along Southold Town's north shore. The width of the beach ranges from 0 feet to 40 feet. Boulders are present on the majority of beaches alternating with areas that consist of beaches with almost no boulders. METHOD The entire beach along Reach 3 was walked to locate areas of actual beach erosion and notable shore protection strnctures. Visible inspection was augmented by the first hand knowledge of the author, with a history of many years of observation of the Long Island Sound shoreline and the descriptions of other observers. The shore line was inspected for areas of severe erosion. The December 24, 1994, storm was one of the worst storms in recent memory in terms of its erosion effects. Areas that received minor erosion as a result of the December storm were not included in the inventory of erosion. Erosion was classified as minor when it resulted in inconsiderable erosion to the base of bluffs, insignificant lowering of the beach grade or other events that would only be excepted in a storm with an occurrence rate of about 20 years, which the December 1994 storm was judged to be in terms of erosion. Reach 3 was subdivided into 9 stretches that generally represent uniform conditions throughout an area of beach, with stretch 1 at Horton's Point and then continuing east. OBSERVATIONS Areas of moderate erosion are noted on the accompanying tax map in orange. Areas of severe erosion are noted in yellow. Areas of hardened shoreline (bulkhead, retaining walls and groins) are noted in blue. Areas where roads may be threatened with erosion in the near future are noted in red. A series of photographs was taken of notable structures and conditions along Reach 3. All photograph locations and measurements are approximate. The first 4,400 feet (stretch 1) east of Horton's point consists of high bluff with a relatively broad beach strewn with boulders. This area is notable for a lack of shore protection structures. The bluff in this area has experienced slides in many locations. The erosion can best be categorized as moderate and was apparently the result of the December 1994 storm. The lack of shore protection structures and the Reach 3 apparent stability of beach access structures seem to indicate that this beach stretch is relatively stabile. An abrupt transition occurs approximately half way between Horton's Point and Southold Town Beach. The high bluff continues but the broad beach and boulders are no longer present. The beach is characterized by shore protection structures as indicated in photographs 6 through 22. These photographs illustrate the severe erosion that has occurred in this stretch. Stretch 2 includes Southold Town Beach. Southold Town Beach is notable because it has no boulders and no bluff. This public beach has experienced accelerating erosion as the storm patterns have intensified over the past several years. The erosion of Southold Town Beach appears to be aggravated by the two large groins just to the west of the beach area. Stretch 3 is the area just east of Southold Town beach. It is a short stretch of beach that is strewn with boulders. Stretch 3 is notable for its shore protection structures and its stability. Stretch 3 contains two large groins at its east end. Stretch 4 is a short stretch with no boulders and a low bluff. This area is subject to severe erosion. The erosion is apparently aggravated by the groins at the east end of stretch 3. These two groins are identified as number 2 and 3, Hashamomuck Beach, page 36 of Thore Omholt's 1974 study. The construction of these groins is dated in Omholt's study as 1955 and 1956. However, they were reconstructed in the late 1960's. Three historical observers date the reconstruction of these groins as the starting point for the severe erosion experienced in stretch 4. Erosion in this stretch has reached a critical stage. Two dwellings were condemned by the Southold Town building department after the December 1994 storm when the foundations of the structures were damaged. This area has several shore protection structures and more are in the process of being built. County Road 48 is in peril from erosion in this stretch. This stretch has lost at least 50 feet of beach in the past 30 years. Two rock groins have been built in this area, one in 1969 and one in 1984. These groins have not been effective in holding beach material. Stretch 5 is an area very similar to stretch 3 with boulders, shore protection structures and a stable beach. Stretch 6 is similar to stretch 4. The erosion along stretch 6, from the account of one long term property owner, is not as severe as the erosion along stretch 4. County Road 48 is in peril from erosion in this stretch. Stretch 7 includes the area from the Sound View restaurant to about 2,000 feet east of Inlet Point. This stretch is notable for its lack of bulkheading and its boulder strewn beach. One location just east of the Sound Shore motel is interesting since a large pile of boulders acts as a natural groin. The Suffolk County Department of Public Works is responsible for two precast concrete groins, constructed in 1958, at the west end of this stretch to protect County Road 48. This stretch is relatively stable. The beach in the area of the Sound View restaurant has not changed in 25 years. The grade of the beach in front of the Sound Shore motel eroded in the December 1994 storm. The beach along this stretch is stable. The bluff area east of the motel and condominiums is notable for the lack of serious erosion during the December 1994 storm. The east end of this stretch has a short 2 Reach 3 section of beach with no boulders in the vicinity of Iniet Pond. This section of beach is notable as the only section of beach that has no boulders and is stable. Stretch 8 is the area 2,000 feet east of Inlet Point to 1,000 feet west of the Island's End golf coarse. This are can best be characterized as stable to moderate erosion. Stretch 9 includes the area from the golf coarse to Rocky Point. This stretch is a stable beach. CONCLUSIONS The erosion experienced at various locations along Reach 3 is a function of the quantity of natural boulders present, beach orientation in relation to tree north, man made groins, natural groins, bulkheads and offshore topography. Some man made groins have functioned satisfactory in holding the beach and done little damage to adjacent beaches. The larger man made groins have resulted in stable beaches to the west and severe erosion to the east. The most important elements in determining erosion appears to be the quantity of boulders on the beach, followed by the presence of large man made groins. Most groin construction has taken place in boulder rich areas where the material for construction is readily available. Where groins have been constructed from imported rocks, they have not proven satisfactory due to the small size of the rocks and the shifting nature of the beach itselfi This predisposes beaches free of boulders to be susceptible to erosion. The present policy of the New York State Department of Environmental Conservation to allow groins only to the high water line, if at all, makes beach stabilization difficult. Bulkheads are not a solution to the erosion problem and are effective only in areas of stable beach. Roads are in peril from erosion in three locations: the town road at Sound View Avenue; County Road 48, 2000 feet east of Southold Town Beach and 200 feet west of the Sound View restaurant. RECOMMENDATIONS In an ideal world no construction would be allowed near the shoreline; it would be preserved fo~ public access. This does not appear to be a policy that can be pursued at this point in time. The construction of bulkheads should be allowed to protect property that is in jeopardy from erosion, however bulkheads alone are not effective. Properly engineered groins should be allowed to help stabilize beaches. Existing groins should be studied to determine which combinations of materials, lengths, heights, permeability and location are effective. Groins should be allowed to extend past the high water line in locations that have experienced severe erosion in an effort to stabilize and rebuild beaches. Property owners who have constructed large groins 3 Reach 3 should be encouraged to dismantle a portion of these groins. One mechanism for dismantling of large groins may be through the power of the town trustees to require permits for construction on or near the beach. When property owners request related beach work such as cesspool construction and bulkheading, groin downsizing could be required. The construction of low profile timber groins should be encouraged. Low profile timber groins have been effective on the bay and low profile steel groins were effective on the ocean in rebuilding beaches after the hurricane of 1938. The use of low profile timber groins has two advantages. One: beach material spills over to adjacent beaches when the groin is full, rather then being redirected to deeper water outside of the littoral drift. Two: the life of timber groins is limited so that they could be monitored through the permitting process and permission to rebuild them could be denied where they do not produce the desired result. Parallel or offshore groins should also be considered. If sized properly for the local conditions these structures may be effective in stabilizing beaches (see photo 10). The Town should develop a set of standards for groin construction and require that plans submitted for permit approval in severe erosion areas be made by a professional engineer. 4 Reach 3 Typical erosion stretch 1 2. Typical erosion stretch 1 5 Reach 3 February 1995 3. Retaining wall 4. Close to the edge see photos 5 i Reach 3 February 1995 §. Typical erosion to bluff; stretch 2 Failed bulkhead with 2" sheathing 7 Reach 3 February 1995 7. A structure precariously close to the edge. No bulkhead on either side. 8. Failed timber bulkhead (see photo 11 ) Reach 3 February 1995 Looking east. Beach held by a parallel or offshore groin. 10, Looking northwest. The effectiveness of a parallel or offshore groin is apparent from these two photos. Reach 3 February1995 Looking west, hardened shoreline, failed bulkhead '12. I,ooking east, hardened shoreline. Notice ineffective concrete groin. l0 Reach 3 February 1995 '13. Massive concrete seawall. Base of wall is being undermined. '14. Concrete groin visible in photos 12 & 13. This groin is too short to be effective and too high for access along the shore. Reach 3 February1995 '16. This bluff was entirely covered with paving stones set in concrete in the 1970's. The armor stretched from the base of the bluff to the top. 12 Reach 3 February 1995 .17. Littoral drift- a paving stone 250' east of the armored bluff in 15 &16. '18. 750' east t bluff '13 Reach 3 February t995 Failed bulkhead, possible public health hazard. 14 Reach 3 February 1995 20 8, 21. Looking east. A large groin effectively holds the beach. This structure is too long and directs the littoral flow material to deep water where it is lost to the littoral drift. The bar created by this groin can be seen at low tide, when the wind is northwest, from Southold Town Beach. Reach 3 February 1995 22. Failed rock gabions east of the second groin in photo 21. Reach 3 February 1995 23. Sand placed over bluffin an attempt to stabilize it. 24. Looking west. Notice 2 groins in photo 2l. Sound View Ave. is visible in left of photo. Reach 3 February 1995 25. Ineffective west rock groin, stretch 4 26. Ineffective east rock groin, stretch 4 Reach 3 February 1995 27. Erosion damage, stretch 4 Reach 3 February 1995 28. West county groin, Sound View restaurant 29. East county groin. Sound View restaurant 2O Reach 3 February 1995 30. West groin, Sound Shore motel 3'1. East groin at motel. Notice high timber groin which impedes acceSS and traps all littoral drift. 21 Reach 3 February 1995 32. Grade drop in December 1994 storm is evidenced by exposed drainage structure at motel. 33. Exposed drainage structure 22 Reach 3 Febmary1995 34. Grade drop is evidenced by paint line on pool at motel. 35. Natural rock groin, looking west 23 Reach 3 Febmary 1995 36. Natural rock groin, looking east 37. Typical beach} stretch 7 24 Reach 3 February1995 38. Natural groin 39. Typical erosion 25 Reach 3 February 1995 40. 67 Steps (Som~d Road end) 41. Rocks, looking west 26 Reach 3 February 1995 42. Rocks, looking south 43. Rocks, looking east 27 Reach 3 February1995 44. Rocky Point, looking west, low tide 45. Rocky Point, looking east, low tide 28 Reach 3 February 1995 3 I ! REACH 3: HORTON POINT TO ROCKYPOINT Pg.1 of 5 I': 727~ Map~West Section 29 Reach 3 February 1995 ! I hood' I Map~East Section I Average High Boulders Moderate Boulders 2 Narrow High Few Boulders Severe Clay Bluff Road in peril 3 ~ Average Low Moderate Boulders Stable Stable Beach 4 Narrow Low No Boulders Severe Erosion Road in peril 5 Average Low Moderate Boulders Stable Stable Beach 6 Narrow Low Few Boulders Severe Erosion Road in peril 7 Average High Boulders Stable Stable Beach 8 Average High Boulders Moderate Boulders 9 Broad High Moderate Boulders Stable Stable Beach Table of Reach 3 Characteristics 31