Å˽ðÁ«´«Ã½Ó³»­

A study by researchers at North Carolina State University supports what some critics of federal flood maps have said for years: That lines drawn on a map give a false sense of security from flooding and have led to increased development in vulnerable areas.

The “safe development paradox” has meant that very near the edge of the 100-year flood zone, or the Federal Emergency Management Agency’s special flood hazard area, development has boomed, increasing the risk of insured and uninsured losses.

The study examined 2,300 counties nationwide and found that as much as 24% of all development occurs within 250 meters of the boundary of the designated 100-year flood zone, . The authors expect this trend to continue through the year 2060 unless new policies are adopted.

The flood maps “communicate flood risk in a way that says you are either on the ‘at risk’ side of that line, or the ‘minimal risk’ side,” lead author Georgiana Sanchez said in a report by NC State.

But properties just outside the flood zones may be just as vulnerable, especially as storms and rainfall amounts appear to be on the rise in much of the country. This was painfully apparent in Hurricane Helene, which dumped unprecedented rainfall on western North Carolina in September 2024 and flooded hundreds of structures, many of which were outside the hazard area and did not carry flood insurance.

“Because of the steep topography in places like western North Carolina, there is an even greater concentration of development compared to flatter areas,” Sanchez said. “Developers tend to seek land that is flat enough to build on, which often happens to be along stream networks and closer to flood-prone areas.”

Even before Helene, there was Hurricane Florence, which impacted parts of North Carolina. The study found that in Beaufort County, North Carolina, most of the flooded buildings were within the designated floodplain. But another 23% of flooded structures – almost 2,000 buildings – were just outside the FEMA zone, “an area FEMA flood maps designate as having ‘minimal’ flood risk,” the study noted.

The analysis examined data from 2001 through 2019 and did not look at the effect that FEMA’s Risk Rating 2.0 may have on development in flood-risk areas. Risk Rating 2.0, which began in 2021, is designed to give a more precise risk assessment, based on many factors, for properties within the special flood hazard areas. It does not examine areas outside the zone, FEMA officials have said.

“I wouldn’t be surprised if (Risk Rating 2.0) remains understudied, given its focus on recalculating premiums within the 100-year floodplain, while the broader issue is that damage often extends far beyond that boundary,” Sanchez told Å˽ðÁ«´«Ã½Ó³»­ Journal.

The recent study by Sanchez and other researchers at NC State was published in PLOS One, an open-access, peer-reviewed journal. It came out in December, two years after Sanchez and team produced another study that showed how FEMA flood maps can be misleading about water risk outside the flood zone, causing many vulnerable properties to forego flood insurance.

“Unfortunately, FEMA’s flood maps underestimate the risk of flooding by failing to account for intense rainfall events and sea level rise,” notes an NC State report about the 2022 study. “These conditions are becoming more common as climate change accelerates, increasing the likelihood and seriousness of flooding.”

Å˽ðÁ«´«Ã½Ó³»­ agents, flood insurance carriers and others have repeatedly urged more Americans to consider flood insurance, even for areas where flooding is not frequent.

Top photo: The Impact Plastics plant in Erwin, Tennessee, where six people were swept away and killed in river flooding caused by Hurricane Helene in September. The plant is just outside FEMA’s 100-year flood hazard zone, according to news reports.

Report: More Than 250,000 Properties Have Repeated Flood Claims

Topics Flood North Carolina