Interim measures in place to prevent flooding from Addicks, Barker reservoirs
As development in the Cypress Creek watershed in northwest Harris County continues, it could put more strain on the downstream Addicks and Barker reservoirs, which have an "extremely high risk" of failing, according to the U.S. Army Corp of Engineers.
If the dams fail, it could potentially flood Buffalo Bayou and parts of west and downtown Houston.
"I think it's important to note that Addicks and Barker are two of the best flood control investments we've made in Harris County," said Jim Blackburn, environmental lawyer with the firm Blackburn and Carter. "We should do everything we can to protect the integrity of those investments. I'm concerned we aren't acting in protective interests."
The Corp operates the structures and has plans to fix two areas of concern: issues with the outflow structures and uncontrolled auxilliary spillways at the ends of the dams. Improvements are expected to begin by mid-2014 and be complete by 2017. Due to pending litigation, the Corp was unavailable for comment.
The reservoirs
Built in response to two major flooding events in downtown Houston, the Addicks and Barker reservoirs opened in the 1940s to protect residents along Buffalo Bayou. In addition to the two reservoirs, Corp plans called for the development of a White Oak reservoir, a levee to keep Cypress Creek from overflowing into Addicks Reservoir, and two channels to divert floodwater around the city of Houston, none of which were constructed, according to Blackburn.
Although the reservoirs have prevented about $6.4 billion in potential flood damage, according to the Corp, their "extremely high" risk of failure is a concern for some officials in Houston. During an Oct. 2 meeting facilitated by Blackburn, several officials gathered to discuss the issue and what can be done in the future.
"One of the problems is a leakage they found occurring under the culverts," said Lawrence Dunbar, engineer with Dunbar Harder PLLC, who spoke at the meeting. "Their thought is to build a new set of gates next to the current ones and then eliminate the current ones to stop the leak."
The Corp combines safety risks and potential consequences when determining the dam safety rankings. Since the Addicks and Barker reservoirs protect such a heavily populated area, the consequences of failure are greater than if they were located outside such a big city, according to the Corp.
Until the permanent fixes are made to the structures, the Corp has begun filling voids around the conduits that drain water from the reservoirs, installing additional monitoring points around the outlet structures, adding generators to ensure uninterrupted power to the water control structures and a new filter around the outlet works conduits to prevent holes from forming in the future.
Development concerns
Construction on Segment E of the Grand Parkway, which will run from Hwy. 290 to I-10 upstream of the reservoirs, is expected to be complete by late 2013, but the potential of increased development spurred by the roadway has brought up concerns in regards to flooding.
"When we build our cities, when it rains on that landscape, the water concentrates in minutes," Kevin Shanley, CEO of the SWA Group, said during the Oct. 2 meeting. "There was [historically] horrible flooding downtown with almost no development in the watershed, so it's not that development caused all the flooding we have suffered from, but we aren't helping things."
A wetlands permit was needed before construction on Segment E could begin, since the corridor runs through the Katy Prairie, an historic wetlands area that spans 1,000 miles in southeast Texas. Shortly after the permit was granted in mid-2011, the Sierra Club—a national environmental organization—filed a lawsuit over flooding concerns in regards to the reservoirs downstream.
In late August, Federal Judge Keith Ellison ruled that the Army Corp would need to re-evaluate how Segment E will affect the reservoirs.
"With the [Grand] Parkway going in it potentially opens up that land area; it's the impact of land development associated with the Grand Parkway that is of importance," said Blackburn, who represented the Sierra Club in the suit.
According to Ellison's ruling, the drainage impact study done on Segment E suggested ways to provide drainage and mitigation along the roadway, which will hopefully stop more water from flowing downstream to the reservoirs.
"We need to make more capacity within the watershed to retain water, whether you do it in the reservoir, upstream of the reservoir or in Cypress to keep overflow from coming," Dunbar said. "Somehow you've got to stop sending so much water to Addicks and Barker because frankly, they were never designed to handle as much water as we're sending."
