The Media Keep Saying Houston's Development Caused It to Flood
An engineer explains why that's wrong.
The flood waters from Hurricane Harvey are mercifully receding from Houston. Unfortunately, the flood of hot takes blaming Houston's development for the floods has continued unabated.
Despite repeated debunking from a wide range of commentators and urban policy experts, the idea that unregulated development caused the massive swell of storm water has seamlessly shifted from off-the-cuff observations to conventional wisdom.
"Houston's sprawl gave the city terrible traffic and an outsized pollution footprint even before the hurricane. When the rains came, the vast paved-over area meant that rising waters had nowhere to go," wrote Paul Krugman in his Monday New York Times column. Roane Carney of The Nation made the same claim last week, saying that Houston has witnessed a continual battle between developers who want to pave over green fields and the engineers and scientists who want to stop that in the name of flood prevention.
For a more informed view, I spoke with Neil Sander, a principal at Dynamic Engineering Consultants, P.C. who holds a master's in civil engineering from Johns Hopkins University. Sander has worked on commercial developments in the Houston area for the past five years.
Far from being an unregulated wild west, Sander says, Houston is typical in how it regulates storm water runoff.
"Houston is governed by a number of different storm water ordinances from different entities," he tells Reason. "The City of Houston, Harris County Flood Control District, and the Texas Department of Transportation all limit the amount of water you can release from a development, regardless of how much you pave." These regulations lay out rules for the quantity and rate of storm water runoff allowed from developments and for how that runoff is managed.
One need only look at the City of Houston's Infrastructure Design Manual for evidence of this.
Nearly a quarter of the 400-page manual—which governs everything from traffic signals to easement requirements—is devoted to storm water collection and drainage requirements, dictating how much water must be detained for a given amount of pavement and how quickly that water must be drained from a property. Other rules cover everything from the design and capacity of drainage ditches and culverts to the minimum spacing of storm water inlets.
Asked how well Houston regulates storm water runoff compared to other areas, Sander says the city does it "as well as anyplace else."
"Some places are very heavily overregulated, especially in the Northeast, but there is nothing uniquely awful about Houston," he tells Reason. "They look at all the same measurements that other municipalities look at. Certainly they have hundreds of pages of regulations on the subject."
Sander adds that the post-Harvey focus on impervious surfaces is misplaced.
According to analysis from the University of Wisconsin's Space Science and Engineering Center, Hurricane Harvey was a 1-in-1,000-year event, dumping nearly 20 trillion gallons of water on the Houston area in only a few days. No amount of planning or infrastructure can handle that kind of water, Sander notes. Even for green fields, "little water beyond a two- or five-year event is infiltrating anyway."
Sander suspects that current calls for more comprehensive urban planning are opportunistic. "Somebody has a solution sitting on a self, waiting for what they think is the right opportunity to roll it out," he says. But when it comes to surviving storms like Harvey, "I can say confidently that introducing zoning to Houston would make zero difference."