First, flood-plain zoning focuses on “high-risk” areas, which by definition means areas in the 100-year floodplain. Fannie Mae and Freddie Mac require that homes they mortgage be covered by flood insurance if they are in zone A or V, which means the 100-year floodplain.
But the Houston flooding resulting from tropical storm Harvey was a 1,000-year flood. That means neither zoning nor insurance would have made a difference for the homes outside the 100-year floodplain. At least half of all the homes damaged by Harvey flooding were in the “moderate-risk” zone in the 500-year floodplain but outside the 100-year floodplain, and more were in the low-risk area outside the 500-year floodplain.
Second, zoning is no guarantee that areas will avoid flood damage. Miami-Dade County has zoning. Yet nearly half of the population lives in the 100-year floodplain, and most of the rest live in the 500-year floodplain. No city is going to zone itself out of existence by forbidding development in most of its land area.
Third, as the Antiplanner noted last week, Houston’s low-density development actually makes it less susceptible to flooding. This is supported by my colleague, Vanessa Calder, who observes that more than 60 percent of Houston is permeable, compared with less than 50 percent of New York, Chicago, or Los Angeles. This assumption of many urban planners that low-density suburbs have high rates of impervious development is wrong.
Harvey deluged Houston with trillions of gallons of water, making it the “most extreme rain event” in American history. Given that much rain, says Houston’s Mayor Sylvester Turner, “zoning wouldn’t have changed anything.” If Houston had been zoned, he argues, “We would have been a city with zoning that flooded.” But urban planners have never been shy about twisting the facts to justify their desire to control how everyone else lives.