With more rain on the way, nervous Houstonians may not even be aware that two aging dams stand between them and catastrophe. It’s not a new problem. Check out Steve Jansen’s article in a July 2012 edition of the Houston Press. As if you didn’t have enough to worry about.
Addicks and Barker have also been weakened due to the natural decline of dams that are made out of a big pile of dirt. According to a 2010 study released by the United States Society on Dams, soil and rocks that have been used in dam construction tend to deform, erode and lose strength over time.
As a result, Houston’s most valuable and proven flood-control mechanisms might not be able to protect the city against a 25-year storm event, says Lawrence Dunbar, a former head of the Army Corps of Engineers’ flood control and reservoir regulation section in Chicago.
“The Corps isn’t quite sure how these voids got formed. Therefore, they’re not sure if you get another big rain and the reservoir fills up again, even if it doesn’t get high as it got before, they’re not sure it can hold and voids won’t form again,” says Dunbar, a licensed professional engineer in Texas since 1983.
In the 1980s, the Corps installed concrete walls inside the earthen part of the dam to discourage leakage. However, the concrete wasn’t installed above or below the culverts, which need replacing in the worst way.
“That’s where they found these voids — under the culverts,” says Dunbar. “What happens when a void forms is, it can basically let water blow through under the culverts or through the dam. When that happens, it’s bad and dam failure is imminent. It’s a big concern,” says Dunbar.