Houston was recently victim to the largest rainfall in U.S. history, a 52” deluge from Hurricane Harvey that’s left many parts of the metro still underwater. Houston is also arguably the nation’s least-regulated metro area for land use, featuring a central city that doesn’t even have a zoning code.
This correlation is, apparently, enough for the media to conclude that one has to do with the other.
Various articles this past week — including from Slate, Newsweek and The Atlantic — argued that Houston’s rapid sprawl development worsened the flooding, by increasing the metro’s impervious surface, and thus its runoff problems.
Houston, wrote the Washington Post, “is the largest U.S. city to have no zoning laws, part of a hands-off approach to urban planning that may have contributed to catastrophic flooding from Hurricane Harvey and left thousands of residents in harm’s way.”
The oddest thing about this analysis is that it misses the actual details of Houston’s land-use policy. The city proper, while technically without zoning, still preserves many of the regulations found in other cities, which inhibit density. These include parking minimums, setback requirements and city-endorsed deed restrictions. Bloomberg’s Noah Smith has nicknamed Houston’s mix of deregulation and traditional code enforcement “zoning lite.”
Much of the sprawl development being criticized, meanwhile, wasn’t built in the city anyway. Since 2010, Houston has been America’s fastest-growing metro in net terms, adding 850,000. Only 200,000 of this has been in the city, while the rest has arisen in boomburbs like Katy and Sugar Land. And those municipalities have zoning codes that, again, discourage density.
“This is not a zoning-related problem,” Jim Blackburn, a civil engineering professor at Rice University, said to me about the flooding.
A more valid cause for criticism might be Houston’s explosive growth overall. Beyond the debates about its zoning, or lack thereof, Houston is, for all intents and purposes, the most unfettered market in America. Its population has grown so much because its housing stock has been allowed to grow also. Since 2010, the metro outpaced second-place New York City in housing permits by a whopping 11 percent.
And much of this development has been sprawl. That same Washington Post article included a chart showing Houston’s expansion in impervious surface between 2001 and 2011. It is indeed significant, especially beyond city boundaries, fueling the criticism that this paved-over quality is what exacerbated the flooding. Do these critics have a point?
If science matters, then no, not really. The idea that Houston’s land use decisions were the main cause for flooding is absurd on its face. No amount of regulation will properly absorb or confine a year’s-worth of rainwater falling in 5 days. New York City, which is basically the anti-Houston — a dense, regulated city — was devastated by Superstorm Sandy, when just a few inches of rain and strong winds caused flooding in all 5 boroughs.
And the idea that Houston’s land-use decisions were even a minor factor in the flooding looks increasingly baseless. According to a U.S. geological survey, Houston’s clay-based soil is some of the nation’s least penetrable, making flooding there inevitable. The region’s topography is also abnormally flat, slowing the flow of water to the Gulf Coast.
The metro has tried building infrastructure to address the problem, causing Blackburn, the Rice University professor, to even call it an “overreliance on engineering”. The Harris County Flood Control District has put $4 billion into infrastructure, and tacks on another $100 million each year. A lot of this is underground laterals that feed water into the bayous, which have been channelized with a concrete surface to speed water flow into the Gulf. But they tend to overflow even after rainfalls much lighter than Harvey.
While the impervious surface from development certainly worsens this problem, it can take only so much blame. The wetlands that have been lost to development since 1990 would have absorbed an estimated 4 billion gallons; the rainfall that Harvey dumped onto the Houston area was an estimated 20 trillion gallons.
With that said, Blackburn believes that there are still measures Houston can take to lessen future flooding. This could include the government bolstering its reservoirs, buying and preserving wetlands, and incentivizing farmers to harvest their land, rather than sell it to developers.
But in this era of ongoing catastrophic weather events, he continued, the conversation needs to move away from debates about land-use minutiae, and towards macro-level ones about where Americans should be living.
“What I see in front of us is a much more serious challenge than (zoning),” said Blackburn. “And it really does change some fundamental concepts about how we develop areas, where we develop areas. These are conversations no one is prepared to have in the United States.”
Even if strong growth continues in Houston, it will need to be different — which he believes, counterintuitive to many commentators, should mean more market-oriented. Blackburn said that a FEMA flood insurance program has distorted settlement patterns, incentivizing many to locate near bayous or in flood plains. And he thinks that Houston’s future development will be denser, and built in more elevated areas.
The irony is that Houston, because of its looser regulations, will likelier tolerate such dense development. This contrasts with, say, New Orleans, another flood-prone city where much of the housing remains in flood plains, but where zoning laws restrict construction in wealthier, higher-elevation areas.
Thus, Houston’s lack of zoning and minimal regulation, while not the cause of flooding, may in the future be the greatest control against it.
[This article was originally published by The Hill.]