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Frequently Asked Questions about
the Sea Level Rise Planning Tool

What is the purpose of the tool?

  • The maps and calculator provide elevation guidance for post-Sandy planning and rebuilding and can also guide federal agency planning where appropriate.
  • The maps and calculator are designed to support scenario planning that may help decision makers prepare for and adapt to uncertainties surrounding the future risks posed by sea level rise.
  • 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.

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Why does the tool include both maps and a calculator?

  • 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., depths) during extreme events for the various sea level rise scenarios at 5-year intervals to 2100.

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Who should use the SLR planning tool?

  • 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 tools 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.)

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What counties are included in these Sea Level Rise Tools?

  • The tool provides data for:
    • Nassau and Suffix counties in Long Island
    • The 5 boroughs of New York City
    • Westchester county
    • All coastal counties in New Jersey

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Why is the government releasing another set of maps?  We just got new flood maps.

  • 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 these tools provide.

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Will the new maps define my flood insurance rates associated with the National Flood Insurance Program? Am I required to use these data?

  • No.  These maps and calculator currently 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 critical infrastructure.

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What data are used to generate the tool?

  • 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 NOAA 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 NOAA report or NPCC 2013.

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What is the source of the SLR scenario data? 

  • Most of the sea level rise scenario information comes from 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 tools use 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 scenarios are a part of the climate risk information being use in the Mayor’s Special Initiative on Rebuilding and Resilience and follow on the NPCC 2010 work published by the New York Academy of Sciences in “Climate Change Adaptation in New York City: Building a Risk Management Response.” 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.

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Which sea level rise scenario should I use? 

  • 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.

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Are there other key factors I should consider beyond SLR?

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Photo of Long Beach Island after Hurricane Sandy

Long Beach Island

Photo of Breach at Mantoloking, NJ

Breach at Mantoloking, NJ

Integrated tool partner logos Department of Homeland Security Federal Emergency Management Agency National Oceanic and Atmospheric Administration US Army Corps of Engineers United States Global Change Research Program