If you own a waterfront property and your FEMA flood map shows low risk, you might feel like you have nothing to worry about. That feeling could be one heavy rainstorm away from costing you everything, warns Albert Slap, founder of RiskFootprint™, who has spent over a decade working with property owners, lenders, and due diligence professionals on natural hazard risk.
FEMA flood maps were designed to assess riverine flooding—rivers and streams overflowing their banks—and coastal surge from major storms. However, they do not model rainfall-driven, or pluvial, flooding, which occurs when heavy rain overwhelms drainage systems. For waterfront property owners, this distinction is critical. A property on a bay, canal, or lake may appear low-risk on a FEMA map, but the map says nothing about what happens when several inches of rain fall in a short period.
Many FEMA maps are decades old and have not been updated to reflect changes in land development, drainage infrastructure, or more intense rainfall patterns. The consequences of this gap were devastating during Hurricane Harvey in 2017, when approximately 150,000 homes in the Houston area flooded. Seventy percent of them were in FEMA’s X Zone, the designation for lower risk. Most homeowners had no flood insurance because the map indicated they did not need it. Harvey caused an estimated $125 billion in total damages.
A complete flood assessment must go beyond FEMA maps, integrating rainfall-driven and other flood modeling from sources like NOAA, NASA, and local authorities. RiskFootprint™ uses flood models from Fathom and Swiss Re—tools used by global insurers—to provide a full picture across riverine, coastal, and pluvial flooding. Additionally, a property's vulnerability depends on first-floor elevation. A waterfront home elevated on pilings faces fundamentally different risk than a ground-level slab, even if both appear identical on flood maps. RiskFootprint™ uses AI and machine learning on Google Street View imagery to estimate first-floor elevation for over 300 million U.S. properties.
Slap advises waterfront owners not to treat a low FEMA X Zone as a clean bill of health. He recommends securing flood insurance regardless of zone; federal flood insurance through the NFIP is available to any U.S. property owner. Slap pays $700 a year for coverage on his own home, which sits outside a FEMA zone but has rainfall flood exposure from an adjacent golf course. A complete flood risk assessment for any U.S. residential property is available for $200, providing insight into actual exposure across all flood types.
