Devin Lea, Sarah Pralle
Risk, Hazards & Crisis in Public Policy, May 2021
Flood Insurance Rate Maps (FIRMs) are produced for the National Flood Insurance Program to depict and manage flood hazard in the United States. While past research has portrayed FIRMs as static maps, property residents and community representatives can propose changes to flood zones on FIRMs. These changes add and remove buildings from flood zones on FIRMs, which raises an important question: are there discernable trends or patterns in these alterations to FIRMs?
We use Geographic Information Systems FIRM layers and building footprints to quantify the number of buildings moved in and out of the Special Flood Hazard Area (SFHA) for recently updated FIRMs. Our analysis of building additions and removals from SFHAs at county and census tract scales shows there has been a net change of over 20,000 buildings removed from these SFHAs between preliminary and present FIRM iterations. We also find that SFHAs are more frequently altered in places where median home values are higher, buildings are newer, and percentage of white populations are higher.
These findings suggest changes to flood zones on FIRMs occur more often where people have greater socioeconomic means, raising questions of equity for future FIRM appeals and revisions.
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