How to Manage the Risk?
Managing coastal erosion risks in New York City involves an integrated approach — a combination of major structural controls, environmental controls, and regulatory and policy controls.
To protect the urban environment, New York City has built robust erosion-control structures throughout the five boroughs. Engineered structures on shore or in the water that are properly sited and sized (adhering to buildings codes, such as ASCE 7, for design and construction on vulnerable land) can mitigate the forces of coastal erosion and hold the shoreline in place.
Bulkhead structures and revetments are deployed along waterways throughout New York City’s five boroughs, as shown on this map.
New York City's Natural and Hardened Shorelines
Source: NYC Department of City Planning, 2011
Choosing the most effective erosion-control structure depends on the specific features of the coastal location:
- Seawalls, which may also be considered a type of bulkhead, are massive stone, rock, or concrete structures built parallel to the shoreline and are designed to resist the force of waves that risk eroding the shore by holding the shoreline in place.
- Revetments are sloped structures typically made of stone or concrete blocks to protect the underlying soil from erosion and to minimize the energy of waves. Rip-rap and gabions are common types of revetments.
- Bulkheads are vertical retaining walls, typically made of wood or sheet steel, designed to hold soil in place and stabilize the shoreline.
- Groins are structures that extend perpendicularly from the shore into the water to trap sand, prevent erosion, and break waves.
- Jetties, which tend to be larger than groins, are designed primarily for sediment management and are typically located at the mouth of a river.
- Breakwaters are offshore rock structures situated parallel to the shoreline that break waves to reduce shoreline erosion.
- Artificial reefs are fully or partially submerged structures constructed of rock, concrete, or other materials to break waves, reduce erosive forces on the shoreline, and provide marine habitat.
Groins along the Rockaway Peninsula
Many of the engineered erosion-control structures along our coastline are built in collaboration among New York City, the U.S. Army Corps of Engineers, and the NYS DEC.
Currently, these three government entities are collaborating on the Hurricane Sandy General Reevaluation Report, including a redesigned groinfield near the Rockaway Peninsula. The redesigned groinfield will minimize coastal erosion from longshore drift.
The U.S. Army Corps of Engineers website provides additional detail on the Rockaway Reformulation project and other coastal-erosion projects throughout the region, New York State, and the rest of the nation.
Placing natural and nature based buffers and protective features on the shore or in the water can help maintain the shoreline in place. Environmental control measures include:
- Beach nourishment is the process of placing sand (typically dredged from nearby ocean bottoms) on beaches to increase the elevation and distance between the upland areas and the shoreline. This creates a buffer that diverts storm and wave energy before they hit formerly eroding areas, reducing the risk of flood and dune erosion.
- Vegetation is often planted on beaches, dunes, and unstable shorelines to anchor sand and/or soil in place.
- Living shorelines are made up of plants, sand, or soil, often in combination with hard structures, such as riprap or gabions, to stabilize the shoreline, prevent erosion, and maintain wildlife and marine habitats.
- Constructed wetlands are new or restored tidal wetlands using plants to anchor the soil in place, prevent erosion, and create wildlife habitat.
- Vegetated islands are either fixed or floating offshore structures, such as anchored mats or infill islands that provide ecological benefits and can minimize erosion caused by breaking waves.
Living Shoreline In Brooklyn Bridge Park
Source: NYC DCP, 2013
Since the early twentieth century, New York City has thrived as a major seaport and coastal city due to its many beneficial waterfront developments. Today, approximately 30 percent of the City's coastline is under NYC Parks jurisdictions, including more than 14 miles of beaches that New York City protects and manages for public use and enjoyment. Since 1975 New York City has facilitated placement of an estimated 20 million cubic yards of sand on popular Rockaway Peninsula beaches.
New York City works with its state and federal partners to advance coastal protection projects that reduce the long-term risk of damage and loss of life from storms and sea-level rise. Since 2015, the City has collaborated on many projects to deploy hard (e.g., levees, seawalls, groins) and soft (i.e., natural and nature-based) coastal-erosion protection that have progressed from the initial feasibility study phase through conceptual design and toward final design and construction.
New York State is also working in partnership with New York City’s Department of Parks & Recreation and the Mayor’s Office of Resiliency on a project that will employ ecologically-enhanced breakwaters in the Raritan Bay. This project is designed to reduce or reverse erosion and damage from storm waves, improve the health of Raritan Bay ecosystem, and enhance people’s experience of southern Staten Island’s shoreline (also see Flooding Hazard Profile).Beach Nourishment At Rockaway Beach Source: USACE, 2013
Limiting development in erosion hazard areas and other protective land-use methods can reduce the risk of coastal erosion. The New York City Waterfront Revitalization Program (WRP), which is overseen by the New York City Department of City Planning, creates policies for waterfront planning, preservation, and development projects in the city and ensures they are implemented consistently over the long term.
The WRP is authorized by New York State’s Waterfront Revitalization of Coastal Areas and Inland Waterways Act, which was enacted in response to the Federal Coastal Zone Management Act. The NYS Waterfront Revitalization Act allows each municipality to participate in the State’s Coastal Management Program by preparing and adopting its own local Waterfront Revitalization Program.
The New York State Department of Environmental Conservation enforces regulations within all State-designated Coastal Erosion Hazard Areas (CEHAs), as described earlier. The State's Environmental Conservation Law, which limits coastal development to protect sensitive areas at risk, regulates properties in all CEHAs.
Other types of regulatory measures include the following:
- Construction permits, which are often required to construct or modify existing structures, incorporate coastal-erosion management regulations to ensure that any type of building activity will not accelerate shoreline erosion.
- Setbacks or buffers specify the minimum distance required from the erosion hazard area for certain types of land use or new development. Regulatory setbacks, which are identified on the State's CEHA maps, are only marked in areas having a long-term average erosion rate of one foot or greater per year.
- Development restrictions change the types of zoning allowed in coastal areas or restrict the types of expenditures allowed. For example, the Coastal Barrier Resource Act (CBRA) created federal regulations applicable to different categories of private and public land units along the shore. CBRA provisions restrict use of federal expenditures, such as federal flood insurance, that might otherwise encourage development in at-risk shoreline environments. Areas within the private land units can be developed, provided private developers or other non-federal parties bear the full cost.