Technical Report NPS/NER/NRTR2007/075
Mary K. Foley
The U.S Army Corps of Engineers, New York District is developing engineering plans, including economic costs and benefits, for storm damage reduction along an 83 mile stretch of the coastal barrier islands and beaches on the south shore of Long Island, NY from Fire Island Inlet east to the Montauk Point headland. The plan, expected to include various alternatives for storm protection and erosion mitigation, is referred to as the Fire Island to Montauk Point Reformulation Plan (FIMP). These plans are expected to follow the Corps of Engineers Environmental Operating Principles striving for long term environmental sustainability and balance between environmental protection and protection of human health and property.
Fire Island National Seashore (FIIS), a 19,579 acre unit of the National Park System includes a 32 mile long coastal barrier island located within the FIMP project area. A seven-mile section of the park, Otis Pike Fire Island High Dune Wilderness Area, is also a designated Federal Wilderness Area. The FIIS includes not only the barrier island and sand dunes, but also several islands, sand flats and wetlands landward of the barrier, submerged parts of Great South Bay shoreface, extending approximately 4,000 feet into the bay with the inner shelf region extending approximately 1,000 feet seaward of the Fire Island shoreline.
The Fire Island barrier islands, a sand-starved system dominated by highly dynamic processes, are struggling to maintain their integrity in the face of sea-level rise and storms. Adding to the dilemma is that development on the barriers and the mainland has increased greatly during the past 50 years. As such, managers and decision makers in federal agencies, state agencies and local governments are challenged to balance tradeoffs between protection of lives and property, public access and long term conservation of natural habitats and processes and the plants and animals that depend on these habitats.
National Park Service (NPS) policy stipulates that natural coastal processes be maintained to the greatest extent possible and not be impeded so as to conserve and preserve landforms, habitats and natural ecosystem resources that rely on the landforms and processes for long-term sustainability of the national park. Storms and associated processes such as waves, tides, currents and relative sea-level change are critical elements for the formation and evolution of these barrier islands, sand dunes, back-barrier sand flats and lagoons and vegetated wetlands. Processes such as wave run-up, overwash and barrier beaching, which occur during elevated storm surge are all necessary processes in enabling the efficient transfer of sediments, nutrients and marine water from the Atlantic Ocean across the barriers and into Great South Bay. A large body of scientific data and information published over the past 50 years shows that such transfers of sediment and water from the ocean to the bays are essential for the long-term maintenance of the barrier island and back-bay systems and their biologically diverse habitats and ecosystems. Current relative sea-level rise (~12 in/century) is chronic and pervasive in driving Long Island coastal change and with the likelihood of accelerating sea level rise in the near future, coastal hazards such as erosion, inundation, and storm surge flooding will increase, with corresponding increased risk to life and property on both Fire Island and on the mainland.
In addition, the cumulative effects over the past century and more, both direct and indirect, of human impacts on the Long Island coast have altered the barrier beach and dunes and sediment transport processes. These impacts have likely increased the potential for breaching and increased risk to life and property on the coast and the mainland. Examples of direct impacts are: the stone jetties at Moriches, Shinnecock, and Fire Island tidal inlets and groin field structures at Westhampton that alter littoral processes, armoring and erosion-control stabilization of headlands such as the Montauk Point headlands, and deepening of navigation channels by dredging through the tidal inlets and in the bays. Indirect impacts that have a bearing on decisions to deal with breaching are: high-risk development of the barrier islands and low-lying areas of the mainland vulnerable to flooding, and the dredging of nearshore sand shoals for beach nourishment.
The NPS strives
to employ a coastal management framework for decision making that is
based on assessment of the physical and ecological properties of the
shoreline as well as human welfare and property. In order to protect
developed areas of Fire Island and the mainland from loss of life, flooding,
and other economic and physical damage, the NPS will likely need to
consider allowing artificial closure of some breaches within the FIIS
under certain circumstances. The decision by the NPS to allow breaches
to evolve naturally and possibly close or to allow artificially closing
breaches is based on four criteria:
This report for breach management presents protocols which specify when breach closures within the FIIS might be desirable and necessary, as well as provides recommendations for artificial breach closure engineering operations which are intended to minimize negative impacts to the natural wilderness values and cultural resources within the FIIS, particularly the Otis Pike Wilderness Area. The goal of the plan is to strike a balance between protecting natural resources and allowing natural processes to operate and avoiding loss of life and excessive property damage.
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