Propertied interests and their influence on flood hazard maps in the United States National Flood Insurance Program

Authors: Devin Lea*, University of Oregon, Sarah Pralle, Syracuse University
Topics: Hazards, Risks, and Disasters
Keywords: flood hazard, flood risk, floodplain, social vulnerability, NFIP
Session Type: Paper
Day: 4/4/2019
Start / End Time: 9:55 AM / 11:35 AM
Room: Balcony B, Marriott, Mezzanine Level
Presentation File: No File Uploaded


In the United States, the National Flood Insurance Program (NFIP) produces Flood Insurance Rate Maps (FIRMs) to set insurance premiums based on quantified flood hazard. But despite having a relatively good knowledge of the physical factors influencing predicted flood inundation of FIRM Special Flood Hazard Areas (SFHA), the area predicted to have one percent chance of flooding annually, the contribution of changes to SFHAs initiated by two main interest groups is unknown. These groups are the United States federal government and a group I call “propertied interests”, which includes elected officials, housing developers, and lay people. Both groups can hire technical experts to update depictions of flood hazard on FIRMs, albeit often with different end goals. This research improves understanding of propertied interest ability to change SFHAs on FIRMs and how changes relate to socio-economic variables and property values. Four temporal representations of FIRMs for approximately 100 counties across the United States are used with case study county tax lots to quantify property changes in to and out of the SFHA over time by the federal government and propertied interests before changes in assessed property values are calculated and changes are correlated with socio-economic variables at the census tract scale. Initial findings suggest the success rate of propertied interest-initiated removal from the SFHA is high across socio-economic variables, but a larger percentage of the total requested changes overlap with census tracts with higher socio-economic values like median income and higher assessed property values.

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