How bad is the problem?
Flooding is the most costly type of natural disaster in the U.S., responsible for an average of 140 deaths and $6 billion worth of damage each year. Hurricane Harvey, which dumped 50 inches of rain on Houston last month, was the Texas city’s third “500-year” flood in three years. (A 500-year flood theoretically has a 1-in-500 chance of happening in any given year.) Extreme rainstorms worldwide are up more than a third since the early 1980s. Miami Beach, Fla., experienced 33 flood events between 2006 and 2013, compared with just 16 in the seven preceding years. By the middle of the century, a majority of U.S. coastal areas are expected to be hit with 30 or more days of flooding each year. Harvey wasn’t “the storm of the millennium,” says David Conrad, a consultant for the Association of State Floodplain managers. “It’s going to happen again and again.”