Sea Level Rise Tool for Sandy Recovery
Hurricane Sandy is a vivid reminder that coastal communities are vulnerable to the risk of damage from storms and flooding. Sea level rise increases the frequency and severity of coastal flooding in human and natural systems, even if storm patterns remain the same. FEMA provides information about flood risk based on current conditions. By statutory requirement, FEMA’s Flood Insurance Rate Maps (FIRMs) and other mapping products depict today's flood risk. Addressing flood risk based on current conditions has immediate, short-term benefits to communities, but does not adequately account for increasing flood risk resulting from sea level rise.
Post-Sandy recovery provides an opportunity to reduce vulnerability and increase resilience further into the future by incorporating sea level rise information into decisions about how and where to rebuild, or to start new development. Using the best available science and data, Federal agencies have jointly developed this tool to help state and local officials, community planners, and infrastructure managers understand possible future flood risks from sea level rise and use that information in planning decisions.
Disclaimer: Please contact your local floodplain manager for assistance in interpreting this information. Professional engineers and surveyors can assist in translating this information for recovery planning. These maps and tools have no regulatory implications and do not affect National Flood Insurance Program requirements or rates. Learn more by reading our FAQs.
Sea Level Rise Maps
NOAA, in partnership with FEMA and the U.S. Army Corps of Engineers, has created a set of map services to help communities, residents, and other stakeholders consider risks from future sea level rise in planning for reconstruction following Hurricane Sandy.
These map services, which cover New York City and the states of New York and New Jersey, integrate the best available FEMA flood hazard data for each location with information on future sea level rise from two different peer-reviewed sources:
- A NOAA-led interagency report prepared as input to the National Climate Assessment, Global Sea Level Rise Scenarios for the United States National Climate Assessment. Scientists from multiple Federal agencies and academic institutions synthesized the best available science to create a set of scenarios of global mean sea level rise through 2100. This team considered both ocean warming and melting of mountain glaciers and ice sheets. For all areas in NJ and NY outside the five boroughs, the maps use these global scenarios combined with the best available FEMA flood hazard data.
- The 2013 New York City Panel on Climate Change report, Climate Risk Information 2013: Observations, Climate Change Projections, and Maps. Experts convened by Mayor Michael Bloomberg’s Office of Long Term Planning and Sustainability developed regional sea level rise scenarios for the five boroughs in New York City out to 2050 (now updated to include 2080 and 2100). These scenarios include sea level rise from both ocean warming and ice sheet melt, and factor in local conditions such as vertical land movement and regional climate variations. For all areas inside the five boroughs of NYC, the maps use these scenarios combined with the best available FEMA flood hazard data.
These maps show the horizontal expansion of the floodplain associated with a future increase in sea level in 2050 and 2100 (2050, 2080, and 2100 for NYC), highlighting areas that will be at risk in the future to flood inundation from the 1% annual chance flood event.
Flood Elevation Calculator
The U.S. Army Corps of Engineers, in partnership with FEMA and NOAA, has modified its existing Sea-Level Change Calculator to integrate FEMA’s best available elevation data with the same two peer-reviewed sources of information on future sea level rise used in the NOAA maps and described above.
The Corps sea level change calculator tool complements the NOAA maps by providing site-specific detail on projected flood elevations for 5-year intervals from 2010 to 2100. Such information can be used by floodplain managers, professional engineers, and surveyors, in conjunction with other local information, for developing additional safety margins above the FEMA best available elevation data.
Included with the calculator tool are simplified tables of future flood elevations above the ABFEs in NY and NJ under the different sea level rise scenarios.
Please contact your local floodplain manager for assistance in interpreting this information. Professional engineers and surveyors can assist in translating this information for recovery planning.
- What is the purpose of the sea level rise tool?
- Why does the tool include both maps and a calculator?
- Who should use the sea level rise planning tool?
- Which counties are included in this sea level rise tool?
- Why is the government releasing another set of maps?
- Will the new maps affect my flood insurance rates associated with the National Flood Insurance Program? Am I required to use this data?
- What data are used to generate this tool?
- What is the source of the sea level rise scenario data?
- Which sea level rise scenario should I use?
- Are there other factors I should consider beyond sea level rise?
- Why is the tool different for New York City than the rest of the area?
The maps and calculator provide siting and elevation guidance for post-Sandy planning and rebuilding and can also guide Federal agency planning where appropriate.
They help make transparent the level of risk accepted under different scientific assumptions underlying the expected rate of sea level rise in the 21st century.
The maps and the calculator are complementary.
The maps delineate future risks posed by extreme events, in this case the 1% annual chance flood as defined by FEMA’s best available flood hazard data, with different scenarios of sea level rise added to them. The NOAA future flood risk maps associated with this tool visualize the horizontal expansion of the existing floodplain over broad spatial scales and longer-range planning horizons. The NOAA maps do not denote future flood depths within this horizontal extent.
For site-specific detail, the USACE has adapted their existing sea level rise calculator for users to estimate future flood elevations (i.e., flood depths) during extreme events for the various sea level rise scenarios at 5-year intervals to 2100.
The SLR planning tool is designed primarily to assist long-term planning efforts in states and communities. Those who should be aware of these products and tool include:
- Congressional representatives
- State and New York City (NYC) elected officials
- State and local planners and floodplain managers (e.g., officials who enforce zoning ordinances or building codes, or make policy decisions regarding development, infrastructure, citing, sustainability, etc.)
- Engineering and planning consultants and related professional communities (e.g., local chapters of associations such as ASCE, ASFPM, APA, etc.)
In New York:
- Nassau and Suffolk counties in Long Island
- Westchester county
- All of New York City (Bronx, Kings, New York, Queens, Richmond Counties)
In New Jersey:
- Cape May, Atlantic, Ocean, Monmouth, Middlesex, Union, Essex, Burlington, Bergen, and Hudson counties
- Cumberland, Salem, Gloucester and Camden counties will be added when new data are available.
FEMA generates a number of products, including Advisory Base Flood Elevation maps (ABFEs) and Flood Insurance Rate Maps (FIRM). By statutory requirement, FEMA's mapping products depict today's flood risk and are a basis for current flood insurance rates.
FEMA encourages homeowners to build above their base flood elevation in order to better mitigate their risk and to potentially lower their flood insurance rates.
In order to reduce vulnerability and increase resilience further into the future, long-term decisions can also incorporate information on future risk, such as sea level rise projections. That additional information is what this tool provides.
Will the new maps affect my flood insurance rates associated with the National Flood Insurance Program? Am I required to use this data?
No. These maps and calculator have no regulatory implication and do not impact National Flood Insurance Program requirements or rates.
Use of these data is not required, although we recommend considering them in long-term planning or decisions related to siting and construction of long-lived infrastructure.
The NOAA SLR maps are based on the best available high accuracy elevation data for NY and NJ from various sources (provided in the metadata), the base flood elevations from the FEMA maps (rounded to the nearest foot), and future SLR projections from the Global SLR Scenarios Report or NPCC 2013.
The USACE SLR Calculator is based on the base flood elevations from the FEMA maps (rounded to the nearest foot), published quadratic equations that enable calculation of SLR amounts over time, and future SLR projections from the Global SLR Scenarios Report or NPCC 2013.
Please note that for New York City the calculator only provides data for 2020, 2050, 2080, and 2100. Five-year increments are not available for NYC as they are for the rest of the region.
Most of the sea level rise scenario information comes from a NOAA-led interagency report “Global Sea Level Rise Scenarios for the United States National Climate Assessment.” Scientists from multiple Federal agencies and academic institutions synthesized the best available science to create a set of scenarios of global mean sea level rise through 2100. This team considered both ocean warming and melting of mountain glaciers and ice sheets. For all areas in NJ and NY outside New York City, the tool uses these global scenarios coupled with locally specific information on vertical land movement.
For New York City, the tool uses sea level rise scenarios developed by the New York City Panel on Climate Change (NPCC) Climate Risk Information 2013, which was convened by Mayor Michael Bloomberg’s Office of Long Term Planning and Sustainability. These are regionalized projections based on thermal expansion of the ocean, dynamical changes in ocean height, land subsidence, land-water storage, land-based ice loss, and regional responses to land-based ice loss. The projections are for 2020 and 2050 (now updated to included 2080 and 2100). Please use the following citation for the NPCC scenarios: New York City Panel on Climate Change, 2013: Climate Risk Information 2013: Observations, Climate Change Projections, and Maps. C. Rosenzweig and W. Solecki (Editors), NPCC2. Prepared for use by the City of New York Special Initiative on Rebuilding and Resiliency. New York, NY.
The lower-rise scenarios may be appropriate where there is a high tolerance for risk (e.g., projects with a short lifespan or planning areas with flexibility to make alternative choices within the near-term). These scenarios primarily address ocean warming and do not include potential major contributions from ice sheet melting.
The higher-rise scenarios should be considered in situations where there is little tolerance for risk, such as projects with a long lifespan, where losses would be catastrophic, where there is limited flexibility to adapt in the near- or long-term, and those that serve critical economic and ecological function (e.g., ports or endangered species refuges). These scenarios primarily address both ocean warming and contributions to sea level from ice sheets.
Thresholds based on site conditions may also influence your choice in choosing a value of sea level rise for planning or design purposes. For example, if a 4-foot sea level change could result in catastrophic loss (such as overtopping a dune), then designs for this condition should be evaluated in the range of options.
Coastal flood risk is related to multiple factors. The new tool provides information on future sea level rise. Assumptions about the combination of future storm surge, wave heights, and long-term beach erosion on top of future sea levels can also significantly affect future risks. Data that can be combined with the tool to help assess these interacting issues can be found with the U.S. Geological Survey:
- Assessments of historical long-term and short-term shoreline rates of change for the U.S. Mid-Atlantic.
- Probabilistic predictions of shoreline change in response to different future sea-level-rise scenarios
- Data series showing topography, dune elevations, and mean-high-water shoreline position for most sandy beaches in Fire Island, New York, and from Cape Henlopen, Delaware to Cape Lookout, North Carolina
Since New York City had generated their own science-based sea level rise scenarios through a different process, the Federal agencies wanted to provide the tool to accommodate these data.
In addition, the scenarios are discrete data points, so they are only available for 2020, 2050, 2080, and 2100. This means that in the SLR Calculator, only those points are presented and not the 5-year intervals that are available for the other areas.