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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 1 1 3 4 4 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 0 Scale N No Scale $ 0 U /'~ D Horlon Pt. Bittner I Mile Gr~ ' /' Duck Pond Goldsmith Point Z hie t LON6 isLA ND $oUHO ~Ha * ~ Rlverhoad A .~ i. A rJ '~ I c ~hngTon I Smithtow~. · ~ _ __j Brookhaven - I !-'S-U'F F 0 L I~ '-O0~JNTY ! I Sou 0c FIGURE ! 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