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Governments Plan for Development of Land Vulnerable to Rising Sea Level: New York

J.J. Tanski. 2010. "New York". In The Likelihood of Shore Protection along the Atlantic Coast of the United States. Edited by James G. Titus and Daniel Hudgens. Report to the U.S. Environmental Protection Agency.

The summary is on this page. You can also download a printer quality version of this New York sea level rise planning study (pdf 2.8 MB, 63 pp), which was originally prepared by New York Sea Grant.


Sea level is rising approximately one inch about every eight years along the coast of New York. Ocean shores are eroding along the Atlantic coast. Marshes are eroding in Jamaica Bay, and high tides now flood some streets in developed areas. These effects would become more commonplace if rising global temperatures cause the rate of sea level rise to accelerate. The Intergovernmental Panel on Climate Change, for example, estimates that by the end of the next century, sea level is likely to be rising 0 to 3 inches per decade more rapidly than today (excluding the possible impacts of increased ice discharges from the Greenland and Antarctic ice sheets).

Rising sea level erodes beaches, drowns wetlands, submerges low-lying lands, exacerbates coastal flooding, and increases the salinity of estuaries and aquifers. Coastal communities must ultimately choose between one of three general responses: " Armor the shore with seawalls, dikes, revetments, bulkheads, and other structures. This approach preserves existing land uses, but wetlands and beaches are squeezed between the development and the rising sea. " Elevate the land and perhaps the wetlands and beaches as well. This approach can preserve both the natural shores and existing land uses, but often costs more than shoreline armoring. " Retreat by allowing the wetlands and beaches to take over land that is dry today. This approach can preserve natural shores, but existing land uses are lost.

Each of these approaches are being pursued somewhere in the New York. Bulkheads are common along the shores of New York City and Long Island. The Corps of Engineers has placed sand onto ocean beaches on the south shore of Long Island. Homes have been lost to retreating ocean shores in South Hampton.

Nevertheless, there is no explicit plan for the fate of most low-lying coastal lands as sea level rises. Environmental planners do not know whether to assume that the coastal wetlands will be lost or simply migrate inland. Those who plan coastal infrastructure do not know whether to assume that a given area will be submerged by rising waters or protected from the sea. And even in developed areas that will presumably be protected, public works departments do not know whether to assume that the land surfaces will gradually be elevated or that the area will be protected with a dike.

This report develops maps that distinguish shores that are likely to be protected from the sea from those areas that are likely to be submerged, assuming current coastal policies, development trends, and shore protection practices. Our purpose is primarily to promote the dialogue by which society decides where people will yield the right of way to the inland migration of wetlands and beaches, and where we will hold back the sea. A key step in evaluating whether new policies are needed is to evaluate what would happen under current policies. The maps in this report represent neither a recommendation nor an unconditional forecast of what will happen, but simply the likelihood that shores would be protected if current trends continue.

New York Sea Grant obtained land use and planning data from Suffolk, Nassau, and Westchester Counties and New York City. He also consulted with planners representing the state, New York City boroughs, and the three counties along the Atlantic Ocean, Long Island Sound and the Hudson River as well as the Town of Hempstead in Nassau County. The result is a statewide series of maps that uses existing data, filtered through the town, borough, and county governments who coordinate land use planning activities.

By "shore protection" we mean activities that prevent dry land from converting to either wetland or water. Activities that protect coastal wetlands from eroding or being submerged were outside the scope of this study. This study does not analyze the timing of possible shore protection; it simply examines whether land would be protected once it became threatened. Nor does it analyze whether shore protection is likely to be a transitional response or sustained indefinitely.

The sea level rise planning maps divide the dry land close to sea level into four categories of shore protection:
---Shore protection almost certain (brown);
---Shore protection likely (red);
---Shore protection unlikely (blue); and
---No shore protection, i.e. protection is prohibited by existing policies (light green).

For reasons related to data quality, our study area includes lands within 17-18 feet (5 meters) above the tides. (New York Sea Grant did not project the fates of secured federal installations but depicted them in red so that they stand out.)

One can also view these maps as representing three shore protection scenarios. For example, in an "enhanced wetland migration" scenario, only the areas depicted in brown would be protected; but in an "enhanced shore protection" scenario, only the areas depicted in light green would be submerged. Thus the prospects for shore protection are best understood in the areas shown in brown and light green, while those shown in red and blue are most amenable to coastal planning.

The summary map shows our assessment of the likelihood of shore protection for the coastal zone of New York, and adjacent areas in New Jersey, Connecticut, and Rhode Island. Table 1 quantifies the area of land within approximately three feet (one meter) above spring high water for each of the shore protection categories by county. Table 2 quantifies the length of New York's shoreline along the Atlantic Ocean, Long Island Sound, and Hudson River/New York Harbor.


1. Shore protection is likely or certain along most of the New York coast.
---All but 9 miles of the state's 119-mile Atlantic shore is likely or certain to be protected.
---All but 9 miles of the state's 148-mile Long Island shore is likely or certain to be protected
---Of the 63 square miles of dry land within approximately three feet (one meter) above the tides, 56 square miles is likely or almost certain to be protected.

2. Lightly developed barrier islands in New York are likely to be protected
---Although some shore erosion will be tolerated, the major through highways along these islands makes some sort of shore protection likely (but not certain).
---The mainland behind these barrier islands is densely populated. Therefore, officials are unlikely to allow the barrier islands to disintegrate, which would expose low-lying mainland communities to hazardous flooding.

3. Wetland migration is possible along many of the shores that our maps depict as likely or certain to be protected.
---Unlike most other mid-Atlantic states, New York's regulations do not provide riparian property owners with a right to hold back the sea.
---New York's tidal wetland regulations extend 300 feet inland of the wetlands. State officials believe that the regulations could potentially facilitate a landward migration of wetlands as sea level rises.
---Our maps were designed to provide a broad scale depiction of what would occur given current policies and practices. Site-specific variations from the overall trends may occur, and policies may change over time.

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Governments Plan for Development of Most Land Vulnerable to Rising Sea (PDF, 7 pp., 1.3 MB) was originally published in Environmental Research Letters , Issue 3, Volume 4 (2009).

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