Looking Beyond FEMA Flood Maps, Cities Raise the Bar for Buildings in Floodplains

James Bruggers reports that a number of cities are trying to get ahead of the threat of flooding by putting building standards in place that exceed federal ones. "Hundreds of communities and as many as 22 states already require new construction be elevated higher than federal requirements in the high-risk 100-year floodplain, which is based on a 1 percent chance of flooding in any given year."

Some local municipalities, however, are going even further by applying the standards to buildings in the 500-year floodplain, where flood insurance is voluntary. For example, Mexico Beach, Florida, found that new FEMA flood maps will move 40 homes in the 100-year floodplain to the 500-year floodplain, even though half the homes were destroyed by Hurricane Michael last year. The city passed an ordinance requiring that new construction in both floodplains be elevated at least a foot and a half above FEMA flood predictions, writes Bruggers.

Baltimore, Cedar Falls, and Charlotte and Mecklenburg County in North Carolina have taken similar preemptive measures. After Houston’s experience with Hurricane Harvey, the city started requiring that new development be two feet above expected flood levels, says Bruggers:

The remnants of Hurricane Harvey dumped roughly 50 inches of rain on parts of Houston over four days in August 2017, flooding more than 150,000 homes in that city alone, according to a city study. That study concluded that if all of Houston's homes had been compliant with the city's new rules, 84 percent of the city's homes that flooded during Harvey would have been spared.

Experts say that FEMA flood maps are not accurately assessing risk and that many maps are outdated. FEMA, however, argues that the maps are used for insurance purposes only, and it says it encourages cities to set their own higher standards.