The Dallas levees along the Trinity River are getting a much better grade after reassessment by the Corps of Engineers.
In 2007, the Corps of Engineers pointed out dozens of things the city needed to shore up the levees: erosion control and vegetation management among them. In 2009, the levees flunked the Corps’ inspection using stricter post-Katrina standards. Word was, the ‘fix’ could cost the city millions of dollars.
Colonel R.J. Muraski says the Corps has done a new risk assessment, looking at more sophisticated and varied data.
“We now understand that the system is more resilient than originally evaluated. And there’s less risk associated with the performance of the levees. As we look at the chances of flooding, they are small and would only occur in an extreme case,” Muraski told a City Council committee.
The Corps had said the Dallas levees probably did not even meet the basic 100 year flood protection. But now, Colonel Muraski says the levees have a small one in one thousand chance of overflowing in any given year. And the chances of an erosion failure are hundred times smaller.
That led Council member Scott Griggs to question the wisdom of spending as much as 30 million dollars to build concrete cutoff walls deep into the levees near the Margaret Hunt Hill Bridge where porous sand was found – a possible erosion and leak factor.
“So why are we investing money in a cut off wall if these levees are as good as you say. One in 100-thousand, that’s more secure than probably the whole network of levees and dams over in Copenhagen. So, if the risk of this happening which the cut off wall relates to is one in 100 thousand, why are we building the cut off wall?” Griggs wondered.
City officials say it’s a FEMA thing. The Federal Emergency Management Agency draws the nation’s floodplain maps and requires that certified engineers vouch for levee flood protection. The city’s engineers are recommending the cut off walls.
Dallas Mayor Mike Rawlings says the good news is the Dallas levees are safe. And he says this is a major step toward the promised Trinity River recreation.
“This is important because it’s not just about safety,” the Mayor said. “There’s a lot of plans in place. We’ve got to get some lakes built down there. We’ve got to get some trails built. And we’ve got plans for a highway as well.”
The Mayor says final approval of recreation and roadways within the levees is still pending, but progress is being made.