I suppose this was inevitable.
As thousands of Houstonians recover from the recent storms, the flooding is emerging as a political issue. Mayoral candidates are criticizing the city’s drainage infrastructure, attacking an unfinished project along Brays Bayou – around which much of the flooding occurred – as well as ReBuild Houston, the controversial street and drainage repair program that voters approved in 2010.
Even if the long-term goals of both efforts had been met before Memorial Day, however, experts say the city still would have flooded, as no drainage system could handle the 11 inches of rain that fell overnight in Epps’ and other neighborhoods.
“The rainfall greatly exceeded any design standard for the street system: ReBuild Houston, the old systems, whatever. And the rainfall exceeded any expectation for the bayou systems to contain water,” said Mike Talbott, director of the Harris County Flood Control District. “Any time you exceed the design capacity rainfall event, you’re going to see flooding occur.”
During major downpours, swampy Houston’s first lines of defense are its streets and the underground pipes or roadside ditches alongside them. City storm sewers can send an inch or two of rain over a few hours to the bayous without water pooling in the street, but much more than that will cause road flooding – and this is by design.
The ultimate goal of the city’s current standards, said Carol Haddock, senior assistant director of Houston’s Department of Public Works and Engineering, is to contain a “100-year” rain event – in theory, the worst 1 percent of storms – within the public right of way. That means residents living on any street rebuilt since the early 2000s, when these standards were enacted, should be able to take 13.5 inches of rain in 24 hours without their homes or yards flooding, though their street and sidewalks will be underwater. It’s unclear how many streets have been fully rebuilt under the current standards, but it is certainly no quick task to replace Houston’s more than 8,000 miles of roadway.
What happened with the recent storms, however, saw some areas take nearly that much rain in half the time. Haddock said she is aware of no city that designs to such a standard.
“If everybody wanted us to be able to accommodate every rain event and keep everything open, it would cost every project we build a multiple of what we already spend,” said Wayne Klotz, president of local engineering firm Klotz and Associates and a former president of the American Society of Civil Engineers.
The passage of ReBuild Houston, a program fed largely by a drainage fee levied on property owners, did not change the city’s design standards, but Haddock said the funding it provides will improve drainage by speeding up the replacement of older streets with poor drainage.
Some areas flooded last month because the water could not get to the bayous, Haddock said – that is the city’s job, and what ReBuild is supposed to address. Other neighborhoods flooded, she said, because the bayous had insufficient capacity and broke their banks; improving those channels is the Harris County Flood Control District’s job.
“When Project Brays is done, and 20 years from now, when many of these neighborhoods have been rebuilt, I think the models would predict that we’d fare much better,” Haddock said. “There’s always the possibility that a storm event will exceed what it was designed for, whether you’re talking about pipes or streets or levies or dams. What you’re trying to do is reduce that risk as much as you can.”
These are important issues, but let’s maintain some perspective. No city is built to withstand the kind of rain we were getting without some floods occurring. Whatever you think of ReBuild Houston, we’ve got years to go and many millions of dollars to spend to get a significant number of our streets updated. Go reread that Jim Blackburn piece for some ideas of what kind of questions we should be asking our Mayoral hopefuls going forward. There are a lot of things we’d like to do and that we need to do, but we’re going to have to make a lot of hard decisions about how to prioritize them, and how to pay for them.