Flooding in coastal areas is occurring more frequently than previously estimated, according to a study by North Carolina State University and the University of North Carolina at Chapel Hill. The research highlights significant issues with the conventional method of using marine water level data to estimate flood occurrences.
“Government agencies and researchers use data from tide gauges to measure water levels in coastal areas, then use that data to estimate flood frequency in the region,” says Miyuki Hino, corresponding author of the study and assistant professor at UNC. “However, our study shows that this approach does not accurately capture how often flooding takes place or how long those floods last.”
Katherine Anarde, co-author and assistant professor at NC State, explains that due to sea-level rise, flooding is now observed during regular rain showers or high tides on sunny days. “Our research shows you need land-based measures of flooding to capture the burden on coastal residents,” Anarde says.
The Sunny Day Flooding Project, involving Anarde and Hino, aims to enhance flood monitoring and identify effective mitigation strategies. The study used land-based sensors across eastern North Carolina communities: Beaufort, Carolina Beach, and Sea Level. These sensors recorded significantly more flood days than inferred by traditional thresholds like NOAA’s High Tide Flooding threshold (HTF) and NWS’s minor flood threshold.
Anarde notes discrepancies between sensor data and tidal gauge estimates. For instance, while sensors recorded 122 flood days in Sea Level after excluding extreme storms, the NWS threshold suggested only 31 days based on tidal gauge data.
“In addition to being inaccurate in terms of how often it is flooding, our findings also show that the actual duration of the floods is longer than is captured by the HTF and NWF thresholds,” Hino states.
The researchers emphasize that accurate information on coastal flooding can guide resource investment for building resilient communities. They are collaborating with local partners to develop tailored response strategies for chronic flooding.
“Every community is unique,” says Hino. “But with more accurate data, we can help communities assess what response strategy is best for them.”
The paper titled “Land-based Sensors Reveal High Frequency of Coastal Flooding” was published in Nature Communications Earth & Environment. It includes contributions from Ryan McCune, Thomas Thelen, Elizabeth Farquhar from NC State; Perri Woodard from NC State; Tessa Fridell from UNC; and Anthony Whipple from UNC.
This research received support from various institutions including the U.S. Department of Homeland Security and North Carolina Sea Grant among others.
