Last month, the US Corps of Engineers declared that the Trinity River levees, which the City has been working hard to repair in the last three years, now no longer need further enforcement and are fit to withstand up to a 1,000-year flood. This news, arriving just before the City started construction on $30 million underground concrete walls, was met with much confusion; Why weren’t the levees safe yesterday but they suddenly are today?
Fortunately, Craig Holcomb from the Friends of Fair Park and Trinity Commons Foundation distributed a letter written by Brigadier General Thomas W. Kula of the Corps of Engineers explaining the situation. To introduce the letter, he mentioned a conversation between Mayor Mike Rawlings and the General in which the Mayor asked General Kula whether “political pressure had caused the Corps to change its position on the Dallas levees,” and the General replied, “absolutely not.”
Here is his letter explaining why:
“Friends and Partners,
The Dallas Floodway System and the state of the levees that protect our metro area are topics that are important for all of us.
Last month, our Fort Worth District leadership briefed the Dallas City Council on the results of the Risk Assessment Process, and the results were some good news for both residents and business leaders in Dallas: We now understand that the levees will perform better than previously thought.
This Risk Assessment process helped us better evaluate and understand risk for the Dallas levees in three major areas:
Flood frequency: We previously believed that the likelihood of a storm event creating a flood level that could overtop the levees to be a one in 800 year chance event. Thanks to 20 additional years of flood history, the latest technology, and additional data, we now believe it to be one in 1000-5000 year chance. We will refine the flood frequency estimates to a narrower range this summer.
Flood duration: The estimated flood duration is significantly shorter than originally estimated—from 90 days to a few days—meaning that floodwater is on the levees for a much shorter time, so the levees are less likely to become saturated and fail.
Levee slides: Levee slides have occurred over the years. We were concerned that these slides indicated a more serious problem. But after extensive analysis by geotechnical engineers using the data from more than 5000 borings we concluded that these slides do not pose an unacceptable level of risk.
Based on this new data, along with the 198 corrections performed by the City of Dallas, we have a greater confidence that the levees will perform as they should during a significant flood event.
The attached Corps of Engineers Fact Sheet provides more perspective on this process, and how it helps us better understand the levees.
All of our actions are driven by these key principles:
–Public Safety is our number one priority.
–Levee safety is a shared responsibility.
–Levees reduce risk, they do not eliminate it.
Our goals forward include finishing the Feasibility Study and to continue to identify flood risk reduction measures that help us further protect the citizens of Dallas.
I hope that these facts will help you better understand both the Risk Assessment process and the state of the Dallas levees. We have posted (and will continue to update) information on Risk Assessment and the Dallas Floodway on our Facebook page at www.facebook.com/swdusace.”
BG Thomas W. Kula
CG, Southwestern Division
US Army Corps of Engineers
Dallas, TX 75242
The fact sheet General Kula mentions is below. With the new levee news, the Trinity River Projects should be soon underway.
Featured image from the Dallas Morning News.