More than Heavy Rain Is Flooding Local Lakes. We Are, too.
Nothing like a view of Lake Grapevine from the porch on your waterfront home — unless it's from your back porch.
You know what this unusual season of heavy rain and flooding is really? It’s Mother Nature giving us a big wake-up call. She's telling us we need to go all the way back to zero.
We need to rethink everything we thought we knew about flood control, which is everything we thought we knew about real estate development, which is everything we thought we knew about community.
If we think the flood problems we’ve seen this season have been bad, and if we don’t do anything about them, we’re in for a real nightmare in years soon to come.
In the last month people who live near Lakes Lewisville, Ray Roberts and Grapevine — all owned and operated by the U.S. Army Corps of Engineers — have had the same deal Groucho Marx offers his brother Chico in the The Cocoanuts, an old movie lampooning 1920s Florida land scams:
“I can let you have three lots watering the front,” Groucho says, “or I can let you have three lots fronting the water.”
In neighborhoods assumed safe from flooding, residents are still watching floodwater simmer in the summer heat around their homes weeks after the first heavy rains came. The Corps of Engineers told me last week it may be September before its major reservoirs can be drained back down to the “conservation pool,” or normal level. They said they don’t know when Corps-operated parks around those lakes will be safe for use again.
But here’s the real news. If the city of Dallas and the Army Corps of Engineers proceed with their plans for the Trinity River downtown, all of those flooding problems around the upstream lakes will get significantly worse.
How much worse? Well, we have a problem there. The impact of the Corps’ Dallas Floodway Extension Program on upstream flooding depends on a certain number. We used to know that number. Now the Corps says they can’t find the number any more. It disappeared. Even with all their engineers and scientists, they just can’t come up with that number now.
Here is what the number is about. The full build-out of the Trinity River Floodway Extension in Dallas calls for the erection of new levees downstream from the existing levees. If those levees get built, they will act like an obstruction in the drain at the bottom of a bathtub, backing up the water upstream through downtown.
Backed-up water means higher water in the levees downtown. If water ever backs up too high, overtops the levees and tears them down as happened in New Orleans in 2005, large portions of downtown will be wiped out.
The reason the water is draining so slowly from the upstream lakes now is that the Corps of Engineers, which controls the rate at which water is allowed to leave the lakes, can’t afford to let the water get too high or move too fast between the levees downtown. So they must drain those lakes slowly. Because the lakes are draining slowly, each new major rain fills them back up to overflowing again.
If the new levees get built, they will exacerbate the problem by some amount that scientists can predict. The number. In fact the whole Trinity River project including the massive toll road that the city wants to build between the levees is based on those predictions and that number.
But the Corps told me last week that they could not provide me with the number any more: “The elevation changes that describe the lowering of upstream elevations due to the chain of wetlands or the raising of elevations between the existing levees upstream due to the construction of the Lamar and Cadillac Heights levees are not readily available at this time,” the Corps said in an official statement.
That’s completely crazy. They cannot not know. In fact they have to know with precision how much the new levees will back up the water downtown. This is speculation on my part, but the only reason I can imagine for them not to give me the number is fear. They must be afraid, during this time of flood emergency, that releasing the number will set off a grassroots rebellion in the communities around the upstream lakes.
It should. I know. Because I know the number. It’s two and a half feet. Building the new levees downstream will back up the water in the downtown levee system two and a half feet vertically on the levees.
At the Commerce Street Bridge, flood stage on the river is 30 feet of height on the levees. When the new levees are built, the same amount of water that puts the river at flood stage now will put it two and a half feet above flood stage.
What will that mean to the upstream lakes? It will mean they will have to be drained even more slowly than now. The flooding issues around them will be that much more severe and will last that much longer.
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Wait. How do I know the number if the Corps doesn’t know it? Because it does know it. It has to know it. It couldn’t have proceeded one inch down the road on the whole Trinity River Floodway Extension Project without knowing the number.
And anybody who has followed the project over the years knows it. The number has been out there for 20 years since the project was in its early design stages.
The late Ned Fritz, lawyer and environmental pioneer, was the first critic of the project to tease the two-and-a-half-foot rise number out of Corps documents in the mid-1990s. I sat at a conference table in Fort Worth in 1998 and argued for two and a half hours with an array of Corps experts about the effect of the that much backup. Not a one of them denied the backup will be two and a half feet. But they said they could handle it.
Back then the Corps still wanted to dig a big ditch or “swale” down the middle of the river to offset the rise caused by the new levees. Fritz said they wouldn’t have to dig the ditch if they didn’t build the new levees.
The new levees will protect mainly disused industrial land and a scant number of houses. National and global wisdom on flood control now is that new levees to hold back rivers are a bad idea. They pile up more water and create more flood problems – like stopping up those lakes — than anybody can ever get ahead of.
In more recent years the Corps has decided to grow weeds and stuff in their swale, and they’re calling it a “wetlands.” It’s a ditch with weeds. Most of it is in place already.
The other function of the ditch/wetlands is to offset the proposed bench for the proposed Trinity River toll road. Obviously the bench will push the water up higher on the levees, too. The Corps and the Federal Highway Administration have assured everyone that the bench can be rendered “hydrologically neutral” by digging out the ditch/wetlands some more.
But they have to know how much more. They have to know within inches. Last week when I asked them to give me the current numbers, they said they “are not readily available at this time” but they assured me it’s all going to work out: “The Dallas Floodway Extension Project was modeled as a completed project,” they said, “with all of its features built.”
Translation: Don’t worry your pretty little head how much the new levees will push the river up or how much the ditch/wetlands will lower the river. It’s all going to even out to zero. So why do you care? Why would you want to bother people with this information?
Here’s why. The ditch is already there, most of it. And look what kind of problems we have draining those lakes, even with the ditch in place. When they build the new levees, the problems we are having right now will be multiplied by some significant factor. Things will get worse than they are now, not better.
So why not not build the new levees? Why not not make things worse upstream where all the new development is?
In May 2014, the North Central Texas Council of Governments and the Corps made a joint presentation to the Spring Conference of the Texas Floodplain Managers Association regarding the 1988 Corps of Engineers “Record of Decision.” For more than a quarter century that document and the studies underlying it have been the basis for the region’s flood control strategy.
What the NCTCG and the Corps told the conference a year ago was that a great deal of the real estate development in the region since 1988 did not take place where planners back then thought it would. As a result, the expansion of impervious paved and built surfaces has not gone where planners thought it would. So water runoff into the Trinity River doesn’t work the way planners thought it would — much higher in some places, a little lower in others:
“In some areas, 2005 actual growth exceeded original 2040 projections,” the presentation said. “Development took place in different areas than projected. Urbanization impacts are significant … [impacting] peak runoff rates.”
So here’s the deal. The region’s current flood control strategy is a good quarter century out of date — a period during which phenomenal growth and phenomenal amounts of real estate development have taken place in the watershed, often in ways that have defied projections of planners 25 years ago.
In the current flood emergency, Mother Nature has said, “Look at the lakes, still 10 to 25 feet above flood stage weeks after the first heavy rains. Think about a 25-year-old scheme based on data and assumptions already proven by history to be materially wrong. Then think about the fact that Dallas still intends to do something to make things materially worse.”
We should stop. Go back to zero. Start over.
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