Rains from Hurricane Harvey have caused the Addicks Reservoir to overflow its banks. The 108-foot-deep reservoir sits less than 20 miles west of downtown Houston. Although officials instituted controlled releases of the water behind the dam earlier this week, the additional rains have pushed the flood control system well beyond its capacity. The “uncontrolled release” could endanger neighborhoods all over the city’s west side.
Jeff Lindner, a meteorologist with the Harris County Flood Control District, described the overflow as a “slow rise,” in that the flow of water would be manageable at first. However, as the water levels behind the dam continued to rise, the flow rates over the wall would increase.
“The biggest challenge we face right now is to determine how the flow interacts with the system, and how the water will go as it comes out of the spillway,” he told a local TV station.
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A 2009 report from the U.S. Army Corps of Engineers stated that the Addicks Dam and its sister site, the Barker Dam on the city’s northwest side, were at “extremely high risk of catastrophic failure.” The report came out prior to a surge of urban development on Houston’s west side, including the “Energy Corridor,” a long block of homes and office buildings along Interstate 10 west of the city.
The report also showed that the soil around both the Addicks and Barker dams had subsided. Lawrence Dunbar, a former head of the Army Corps of Engineers’ flood control and reservoir regulation section in Chicago, spoke on the consequences of a dam failure in a 2012 interview with a Houston publication.
“When the reservoir fills up high enough, before it can spill over and out over the concrete part, it will start spilling out over the natural ground, which is dirt, which means it can start eroding right next to the concrete part of the dam,” explains Dunbar. “It would create the same problem as if the concrete wasn’t there.”
In a related story, the levee at Columbia Lakes in Brazoria County failed early Tuesday. Officials posted a simple message to residents on its Twitter feed: “GET OUT NOW!!”