Development of Flood Insurance Maps in New England

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FEMA has requested USGS expertise in hydraulics, hydrology, and mapping to generate flood insurance maps for New England.

USGS employee stands in the river with a prism while a point measurement is taken with a station located on the river bank.

Surface-water modeling for Federal Emergency Management Agency flood insurance rate maps. (Credit: Rena Kalmon, U.S. Geological Survey. Public domain.)

Not only is flooding one of the most common and costly disasters, but flood risk can also change over time because of new development, weather patterns, and other factors. Although the frequency or severity of flood effects cannot be changed, the Federal Emergency Management Agency (FEMA) is working with partners across the Nation to identify flood risk and promote informed planning and development practices to help reduce that risk through the Risk Mapping, Assessment and Planning (Risk MAP) program.

As part of the Risk MAP program, FEMA partners with the USGS to provide communities with flood information and tools they can use to enhance their mitigation plans and take action to better protect their citizens. This work is done through flood risk projects.  In the Risk MAP program, each flood risk project is tailored to the needs and capabilities of each affected community and a strong emphasis is placed on community engagement and partnerships to ensure a whole community approach to reducing flood risk and building more resilient communities.

When conducting flood risk projects, the USGS uses a watershed-based approach. Each watershed study or flood risk project takes about 50 months to complete and has four main steps: discovery, field surveying, hydrology and hydraulics, and flood risk product deliverables. Discovery is the process of data mining, collection, and analysis with the goal of conducting a comprehensive watershed study and initiating communication and mitigation planning discussions with the communities in the watershed. Field surveying is the collection of land survey data for waterbodies identified as high priority by communities during the discovery process. Data collection during field surveying is done using global navigation satellite systems methodology. Hydrology and hydraulics is the use of data collected in the field to create models and floodplain maps. The last step is working with communities and partners to finalize and release flood insurance rate maps (FIRMs) and flood insurance study (FIS) reports.

The Risk MAP program’s flood risk products complement regulatory products to provide flood risk information and support community floodplain management and hazard mitigation strategies. The flood risk products and datasets present information that can enhance hazard mitigation planning activities, especially the risk and vulnerability assessment portion of a hazard mitigation plan, and the development of risk-based mitigation strategies. Flood risk products can also help guide land use and development decisions and help support mitigation action by highlighting areas of highest risk, areas in need of mitigation, and areas of floodplain change.

More information on FEMA flood maps and the Risk MAP program can be found on FEMA’s website: https://www.fema.gov/flood-maps