Standard flood risk due diligence in real estate transactions typically relies on Federal Emergency Management Agency flood maps, documents that are often decades old and designed primarily for riverine and coastal flooding scenarios. According to Albert Slap, founder of RiskFootprint™, this approach misses a critical component: heavy rainfall flooding. "FEMA flood maps don't include heavy rainfall flooding," Slap stated. "They're mostly dealing with riverine-type flood risk." This distinction has profound implications, as rainfall can cause flooding anywhere precipitation occurs.
The limitations of FEMA maps were starkly demonstrated during Hurricane Harvey in 2017, which flooded approximately 150,000 homes in the Houston area. Slap noted that 70% of these flooded homes were located in FEMA's X Zone, areas designated as lower risk for flooding. This extreme rainfall event overwhelmed drainage systems, causing widespread flooding in zones where most property owners did not carry National Flood Insurance Program coverage, resulting in an estimated $125 billion in total damages and massive uninsured economic losses for households and businesses that believed they were in low-risk areas.
For real property buyers, borrowers, and lenders, this creates a significant due diligence gap. Credit officers may review loans using FEMA maps that predate recent storm events, exclude rainfall-driven inundation entirely, and lack incorporation of advanced National Oceanic and Atmospheric Administration storm surge modeling. To provide a more realistic assessment, platforms like RiskFootprint™ are integrating flood models from providers such as Fathom, which is used by global insurers and reinsurers. These models add pluvial, or rainfall-driven, flood modeling alongside riverine and coastal surge scenarios, offering lenders and buyers a more complete picture of property-level flood exposures before transactions close.
Understanding flood exposure is only part of the equation; stakeholders also need to assess whether a specific building is vulnerable to predicted inundation. To bridge the gap from exposure to vulnerability, RiskFootprint™ incorporates estimated first-floor elevation data derived from an AI tool developed by True Flood Risk. This tool uses Google Street View and other imagery, alongside machine learning, to estimate first-floor heights for more than 300 million U.S. buildings. This capability allows the platform to distinguish between a building situated two feet above a predicted flood line and one sitting six inches below it, translating abstract risk into tangible vulnerability.
While FEMA maps serve an important function in NFIP insurance and local building codes, consultants relying solely on them for a complete flood assessment are working with an incomplete picture. Slap argues that conducting a full-spectrum flood assessment before a deal closes—accounting for all water ingress mechanisms, not just those FEMA mapped decades ago—is essential for both understanding risks and protecting consultants from future errors and omissions claims. RiskFootprint™ reports, available for a few hundred dollars per property, aim to make comprehensive flood due diligence accessible for virtually any transaction, whether residential or commercial.
