Nearly half of the North Carolina buildings that took on floodwater between 1996 and 2020 were not inside FEMA’s mapped high-risk zones, according to a new University of North Carolina at Chapel Hill analysis. Researchers logged more than 90,000 structures that flooded at least once and flagged more than 20,000 that flooded repeatedly. The sheer volume of these off-the-map floods is enough to change how planners and homeowners think about risk.
The peer-reviewed paper reconstructed flood footprints for 78 damaging events and used address-level records and high-resolution geospatial data to estimate exposure. According to Earth’s Future, the study trained random-forest models to predict flood damage at 30-meter cells and reported performance that outperformed some process-based and remote-sensing approaches.
“The FEMA 100-year flood plain is really the only public information most people have about their flood risk, but it is imperfect,” said Helena Garcia, the study’s lead author. Antonia Sebastian, a UNC hydrologist who advised the project, added, “Places that have flooded before will flood again.” Those comments and local examples were reported by WRAL…