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USA - Flood Risk Models Vary Widely — Here's What You Need to Know (and How to Mitigate Threats)

With coastal flooding and heavy rainfall on the rise, many homeowners may be unaware of their property’s true flood risk.

Many Americans rely on the Federal Emergency Management Agency (FEMA) to provide accurate information on whether their properties are at risk of flooding. However, according to new 2022 data from First Street Foundation, many properties outside FEMA flood zones may be at risk for flooding.

ValuePenguin home insurance expert Divya Sangameshwar cautions that flood zone risk levels aren’t guaranteed. Homeowners who think they’re safe because they live outside a high-risk flood zone should think twice before opting out of flood insurance.

"Ninety-nine percent of U.S. counties have been affected by a flood in the past 25 years," Sangameshwar says. "The flood maps used to determine your home’s flood risk are built using historic flood data, which may not accurately capture the growing flood risk from climate change."

In this study, we compare FEMA’s Special Flood Hazard Areas (SFHAs) with the First Street Foundation data on properties at risk of flooding. We go over which states are at the highest risk for flooding, where the perceived flood risk is most different and which states may see even more risk in the future.

Key findings

  • FEMA data indicates properties in Louisiana are most at risk for flooding, but a broader First Street Foundation model suggests West Virginia would be the hardest hit. Louisiana has the highest percentage of properties in FEMA’s Special Flood Hazard Areas (23.5%). But the First Street Foundation model — which looks at all properties in a state, not just those in flood areas — shows West Virginia with the highest percentage of homes that would be flooded in a 100-year storm event (29.3%).
  • Perceived flood risk is most different in Hawaii. Just 3.2% of Hawaii properties are in a FEMA flood hazard area, but the First Street Foundation model indicates that 26.1% of properties in the state face at least some risk — a 22.9 percentage point difference.
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