A new study from UNC-Chapel Hill reveals that repetitive flooding in North Carolina is far more common and more widespread than previously recognized, with over 20,000 buildings flooding multiple times between 1996 and 2020. The study, which mapped 78 flood events across roughly three-quarters of the state, fills a major gap in understanding the full impacts of flooding on communities well beyond the state's coastal floodplains.
Until now, detailed flood maps have existed for only a handful of past events. The research team created high-resolution maps for more than 70 previously unmapped floods, linking them to the exact locations of buildings. Their findings show that over 90,000 buildings flooded in at least one event, with 43% of them located outside of FEMA's designated 100-year floodplains, areas officially recognized as high-risk.
"We found that flooding in North Carolina, especially repetitive flooding, is more widespread and frequent than we previously knew, and it is often happening outside of places we currently consider as high-risk," said Helena Garcia, lead author of the study and a PhD candidate in the Environment, Ecology, and Energy Program at UNC-Chapel Hill.
While previous studies and government data have focused on large, headline-grabbing storms like Hurricane Florence or only on insured properties, this study breaks new ground by capturing a much broader and more nuanced view. FEMA's records count roughly 13,000 repetitively flooded properties in the entire state since the 1970s. In contrast, the Carolina team identified more than 20,000 repeatedly flooded buildings from just 1996 to 2020 in a portion of the state where many of these buildings were not covered by flood insurance, meaning they would not have been tracked by insurance records at all.
"We've always known flooding is a threat to NC, but the focus has been on only the biggest events. With this study, we're painting a much more complete picture. There are lots of floods that go under the radar and don't make the headlines, but they are just as damaging and disruptive to the families that are impacted," said Antonia Sebastian, lead advisor and assistant professor in UNC-Chapel Hill's Environment, Ecology, and Energy Program and Department of Earth, Marine, and Environmental Sciences.
The implications of the research are both practical and urgent. By identifying where repetitive flooding has already occurred, the data can help guide smarter, more equitable resilience investments, whether that means strengthening infrastructure, updating emergency planning, or offering better support to affected communities.
"These findings can help guide more effective resilience investments by identifying communities that have been hit hard by flooding but may be currently overlooked by government programs and policies," said Miyuki Hino, co-author and assistant professor in the Department of City and Regional Planning and the Environment, Ecology, and Energy Program.
Their work is already laying the groundwork for further studies on how flooding affects residents over time, from financial strain to health outcomes to migration patterns.
With North Carolina developing a statewide flood resilience strategy, the researchers hope this comprehensive dataset will be used to direct resources where they're needed most, especially in the often-overlooked areas that flood repeatedly but lack visibility or federal aid.
The study is available online in the journal Earth's Future at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025EF006026
