Flood Maps Underrepresent Appalachia’s True Flood Exposure
Federal investments in flood mapping have not kept pace with the need or with increasing climate impacts; thousands of U.S. communities lack maps, and about 15 percent of community flood maps are over 15 years old. More expansive and accurate maps – that account for climate change, and incorporate community views – are needed, particularly in rural Appalachian communities, as historically mapping efforts have targeted higher population areas.
In addition, communities lack sufficiently localized and real-time information about precipitation and river forecasts. Deploying streamgages throughout the region can help generate improved data for forecasting as well as provide local officials and residents with localized river height forecasts and real-time information about rising water levels.
“Understanding the flood problem is like drinking from a fire hose.”
-Bob Martin, West Virginia State Resilience Officer
Flood Mapping and Data Inputs
FEMA - in coordination with local communities - is responsible for developing flood hazard maps. The two categories of these include regulatory and non-regulatory maps.
Regulatory maps are known as Flood Insurance Rate Maps (FIRMs) which are used to determine requirements for flood insurance. Non-regulatory maps include additional flood hazard information, and are meant to provide a more user-friendly analysis of community flood risks.
The National Flood Insurance Program (NFIP) requires FEMA to update and maintain flood maps with respect to all populated areas and areas of possible population growth within the 100-year and 500-year floodplain.
While FEMA collects some of the data for flood maps, the agency also relies on data from other federal agencies as well.
The U.S. Geological Survey (USGS) maintains the National Hydrography Dataset and Watershed Boundary Dataset. These map the U.S. drainage network and surface water areas, and monitor streamflow via USGS streamgages.
The National Oceanic and Atmospheric Administration (NOAA) maps shorelines and precipitation frequency data, the latter of which is collected in the NOAA Atlas. NOAA’s Atlas 14 received dedicated funding from the 2021 Infrastructure Investment and Jobs Act (IIJA) to update the current version of the Atlas to account for climate change and develop precipitation frequency estimates for the entire U.S. and its territories.
State agencies, including local development and water districts, also provide crucial information to FEMA in generating these regulatory maps.
Our Recommendations
Fully funding USGS streamgages, such as appropriating additional funds to the Cooperative Matching Funds program, would maintain a critical lifeline for flood mapping technology in rural communities. Additionally, eliminating the 50/50 cost-share between USGS and local partners would ensure that low-resource communities can access necessary tools for monitoring potential flooding events.