But he said people in those areas should still buy coverage.

“People who have insurance are on a faster road to recovery,” said Mr. Wright, who is now president of the Insurance Institute for Business & Home Safety, an industry-backed research group. “The uninsured are left to rely on friends, neighbors and NGOs.”

A second challenge is that flood threats are now increasingly outside the government- designated risk zone . More than 85 percent of the single-family homes in North Carolina at risk of flooding from Dorian are outside the boundaries of the current 100-year floodplain.

Homeowners outside the floodplain often believe, mistakenly, that they are not at risk of flooding, insurance experts warn. As a result, those homeowners are less likely to buy coverage.

North Carolina demonstrates the size of that difference. Of the homes outside the floodplain that are at risk of flooding from Hurricane Dorian, just 4 percent have flood insurance, Milliman estimated. The gap between insurance levels inside and outside the floodplain is higher than in other parts of the country, like Florida, where people seem to be more aware of the need for insurance, said Mr. Rollins.