When torrents of muddy water filled the Trader Joe’s parking lot at Chapel Hill’s Eastgate Crossing this month, sending shopping carts clattering downstream, business owners were frustrated but not surprised.
The shopping center, built beside Booker Creek, already sits inside the Federal Emergency Management Agency’s special flood hazard area and has filed flood‑insurance claims after past storms.
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What did come as a shock: many of the surrounding homes that also flooded weren’t in FEMA’s high‑risk zone at all.
A peer‑reviewed study released this week by researchers at the University of North Carolina at Chapel Hill shows just how common that disconnect has become statewide.
From 1996 to 2020, 43% of North Carolina buildings that took on water were outside FEMA’s mapped floodplain, the analysis found. More than 90,000 buildings flooded at least once in that period, and over 20,000 flooded repeatedly—double the number captured in federal insurance records.
“The FEMA 100‑year flood plain is really the only public information most people have about their flood risk, but it’s imperfect," said Helena Garcia, lead author and Ph.D. candidate in UNC's environment, ecology and energy program. "We found that many of the buildings that flooded were outside those mapped areas.”
Garcia’s team stitched together National Flood Insurance Program claims, emergency‑service calls and geotagged social‑media posts, then trained a machine‑learning model to recreate 78 flood events in eastern North Carolina. The result is the first address‑level archive of flood footprints for the state.
“Places that have flooded before will flood again,” said Antonia Sebastian, a UNC hydrologist who advised the project. “It’s just a matter of time, and those are risky places.”
No one has completed a formal attribution study of this month’s deluge, but Garcia notes a clear physics link: warmer air holds more moisture, priming storms to dump heavier rain.
As the planet warms, “we’re seeing more intense rainfall events like the one Chapel Hill just experienced,” she said.
FEMA flood maps still decide who must buy insurance, yet coverage remains rare beyond those lines. Only 4% of U.S. homeowners carry flood policies, according to FEMA data cited in an NBC News story on the UNC findings. Rising premiums and insurer pullouts have widened that gap.
“More information about where it has flooded in the past could help people make different decisions,” Garcia said. UNC's archive could guide property owners in choosing insurance even when lenders don’t require it.
FEMA is redesigning its mapping system under an initiative called the Future of Flood Risk Data, promising a fuller view that accounts for climate change. Until those updates arrive, Garcia hopes North Carolina’s database will alert planners and homeowners who assumed they were safe.