Just moments ago I spoke with U.S. Army Corps of Engineers officials at Lake Lewisville and at Corps regional headquarters in Fort Worth, all of whom have assured me there have been no “unusual” releases of water from the six Corps-controlled lakes upstream from Dallas on the Trinity River.
But, uh …
They did release about 5,000 cubic feet per second from Lewisville for a while, about 48 hours ago. That water has already gone through. They say that was no biggie, a minor release.
And, uh …
The river is now at a “flood stage” of 40 feet downtown. Take that to mean it’s about 35-feet deep. Forget about the five-foot difference. Not important, too complicated. It’s 35-feet deep.
Before the storm, the river was at a stage of 25 feet. About 20-feet deep. So in the last several days it has come up 15 feet.
Now, uh …
Records show it can get to about a stage of 50 feet before it overtops the levees. Ten feet to go. The Lake Lewisville release 48 hours ago, which is all gone now, would have been about enough to raise the flood stage 14 inches on the levee. So, according to my math, it would take a release eight or nine times the size of that one to overtop the levees.
Except that, uh …
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There is lots more water going into the river than just the lake releases. You’ve got the City of Dallas, for example, pumping water over the tops of the levees like mad from the sumps -- the areas where runoff from the city gathers. And above the levee system, you have plain old runoff.
Yeah, but, uh …
The Corps told me that the levee system at its present stage is carrying only 20 percent of the water it is designed to hold. So the volume out there would have to increase fivefold to generally overtop and defeat the levees. And that would take a whole lot more rain than we’ve seen so far.
And, uh … that won’t happen. Right? --Jim Schutze