When commercial real estate transactions close, flood risk assessment typically relies on Federal Emergency Management Agency flood maps, documents often decades old that focus primarily on riverine and coastal flooding. According to Albert Slap, founder of RiskFootprint™, this approach creates a dangerous gap in due diligence because FEMA maps were never designed to capture the full spectrum of flood risks affecting properties.
The critical limitation is that FEMA flood maps exclude heavy rainfall flooding, despite the fact that wherever it rains, flooding can occur. This distinction has profound implications for property owners, lenders, and buyers who may believe they are in low-risk areas based on FEMA designations. Hurricane Harvey in 2017 demonstrated this vulnerability when approximately 150,000 Houston-area homes flooded, with 70% located in FEMA's X Zone designated as lower risk for flooding. The rainfall event overwhelmed drainage systems, causing widespread flooding in areas where most property owners did not carry National Flood Insurance Program coverage, resulting in massive uninsured economic losses estimated at $125 billion.
Real property buyers and lenders face this problem at scale, with credit officers often reviewing loans using FEMA maps that predate recent storm events, exclude rainfall-driven inundation entirely, and lack National Oceanic and Atmospheric Administration storm surge modeling advancements from the past decade. To address this gap, RiskFootprint™ integrates flood models and maps from Fathom/Swiss Re, used by global insurers and reinsurers, which add pluvial or rainfall-driven flood modeling alongside riverine and coastal surge scenarios. More information about these integrated approaches is available at https://www.fathom.global.
Beyond flood exposure, stakeholders need to understand actual building vulnerability to predicted inundation. RiskFootprint™ now includes estimated first-floor elevation data from True Flood Risk's artificial intelligence tool, which uses Google Street View and other imagery to provide elevation estimates for more than 300 million U.S. buildings. This allows the platform to distinguish between buildings that sit above flood lines versus those below, moving from mere exposure assessment to actual vulnerability analysis.
While FEMA maps serve important functions in NFIP insurance and local building codes, consultants relying solely on these maps for complete flood assessment are working with incomplete information. The better approach, according to Slap, involves conducting full-spectrum flood assessments before deals close, accounting for all water pathways to buildings rather than just scenarios FEMA mapped decades ago. RiskFootprint™ reports are available for a few hundred dollars per property, making comprehensive flood due diligence accessible on residential and commercial transactions. Additional resources about property assessment methodologies can be found at https://www.astm.org.
The implications extend beyond individual transactions to broader economic stability, as uninsured flood losses disproportionately affect households and businesses operating under false assumptions of low risk. As climate patterns change and extreme rainfall events become more frequent, the gap between FEMA's mapped risks and actual flood vulnerabilities represents a systemic threat to property markets, insurance systems, and community resilience that requires updated assessment methodologies.
