Flood Mapping for Appalachia

By Jessica Arriens, National Wildlife Federation

This blog is part of a series detailing the flood resilience policy roadmap for Appalachia, released by ReImagine Appalachia, Appalachian Citizens’ Law Center and the National Wildlife Federation

Across many parts of the U.S., flooding is becoming more frequent and more severe due to climate change. Which means flood maps, which show a community’s flood risk, are becoming more important tools for homeowners, businesses, and government officials.

Federal investments in flood mapping, however, 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 are needed, particularly in communities across Appalachia, a region uniquely vulnerable to climate-induced flooding.

Besides providing crucial information to inform local development and emergency planning, flood maps determine requirements for flood insurance. The National Flood Insurance Program (NFIP) requires the Federal Emergency Management Agency (FEMA) to update and maintain flood maps with respect to all populated areas and areas of population growth within 100-year and 500-year floodplains.

FEMA uses a mix of data sources from federal and state agencies, local development districts, and more to create its flood maps. The maps don’t always reflect the best available climate science or current climate impacts – especially the extreme rainfall events seen increasingly in Appalachia. A 2020 report from the nonprofit flood risk group First Street Foundation identified nearly 15 million properties with a substantial risk of flooding, which is nearly 68 percent higher than the number of properties identified by FEMA. First Street used flooding from multiple sources (including rainfall and riverine), plus current and future environmental considerations, to calculate substantial flood risk. That inclusion of flood risk from rainfall helped drive the higher number of at-risk properties. According to First Street, 45 percent of the parcels in the four counties that were most impacted by the July 2022 flooding disaster in Eastern Kentucky had a very high risk of flooding, but only 22 percent of those parcels were in a FEMA-designated flood zone.

Earlier this year, NWF, Appalachian Citizens’ Law Center (ACLC), and ReImagine Appalachia released a flood resilience policy roadmap for Appalachia. The platform highlights the unique flooding challenges the entire region faces, and details four sets of policy recommendations to improve Appalachian communities’ ability to respond to and recover from floods. It covers recommendations on ways to improve flood mapping and data inputs, including:

• Deploy more streamgages in Appalachia. One of the key data sources used to create flood maps comes from the U.S. Geological Survey’s (USGS) streamgage network. This network is essential to ensure that communities are warned in time to evacuate areas affected by flooding. Flood alerts and predictions generated by the National Weather Service rely on data generated from USGS-managed streamgages. Streamgages can send alerts to residents to directly notify them of rising stream or water levels. And streamgage data can inform long-term resilience planning. Increasing funding for USGS would enable the agency to deploy additional streamgages, including in rural and disadvantaged communities. 
• Modernize and expand FEMA floodmaps, so communities can know their accurate flood risk. Updated maps should account for anticipated climate impacts, and incorporate mapping of existing natural floodplain areas to understand where protective natural features exist and where they have been lost.

Learn more about the flood resilience policy roadmap for Appalachia here. 

Join a webinar with NWF, Appalachian Citizens’ Law Center, and ReImagine Appalachia to learn more about our coalition’s flood resilience priorities for Appalachia on December 12 from 12-1 p.m. ET. Register here.