Texas is healing fast thanks to all of the great men & women who have been working so hard. But still so much to do. Will be back tomorrow!— Donald J. Trump (@realDonaldTrump) September 1, 2017
Those areas of town I told you might be underwater for a month? That estimate has been upgraded to three months, and a whole new swath of neighborhoods has been added to the "get out now!" list. Because they may be uninhabitable for up to three months, too.
We've gone from flood control to dam protection, although the difference is a moot one:
And then came Harvey. “When that first level of spillway gets overwhelmed, you start storing more and more water behind the reservoir, but at some point you have to release that water because you do not want it to overtop the dam,” says Mark Ogden, a technical specialist with the Association of State Dam Safety Officials.
“Overtopping” is the failure mode. “It’s an earthen embankment, a dirt cross section,” Stannard says. “If water flows uncontrolled over the top, it can erode away the dirt and cause the whole dam to fail.” As of Wednesday night, Addicks had 178,000 acre-feet of water behind its dam, and Barker had almost 170,000. You don’t want all of that hitting the city at once.
The reservoirs filled to record levels. Water got to 109 feet above sea level at Addicks. Areas on the upstream side of the reservoirs flooded. But of course a large release of water from the reservoirs means downstream flooding along Buffalo Bayou, too. “The operation is then a balancing act between how much water you release versus how much you store to keep from overtopping,” Ogden says.
So the Army Corps of Engineers opened the floodgates. Just a little at first, a few hundred cubic feet of water per second, and then wide—7,500 cfs from Barker and 6,300 cfs from Addicks, looking to go up to 8,000 cfs from both later in the week. And the rest of the city is draining into Buffalo Bayou, too. Thousands of houses are flooded. That number might reach 100,000.
It's a devil's bargain. How much worse would it be if the dams failed? As I say, several square miles of residential and business area have been told it would be wise to evacuate; and the expectation is that flooding will continue for three months without another drop of rain falling anywhere around Houston. How long would it last if we just let the water go, and who would be impacted by that?
We don't have flood control in Harris County, not in terms of containing and abating floods. We have flood control in terms of controlling the floods so our flood abatement structures aren't damaged. Everything else is just collateral damage and eggs broken to make our civil engineering omelette.
There are houses on my street that have been flooded for the third time, and owners ware planning to move out. But who is going to move to Houston now? My street isn't on the news, isn't inundated with water, won't be flooded even if the reservoir dams burst. But who would buy the flooded houses on my street? Who will buy those houses across the freeway, in what was once the desirable part of town in west Houston, the houses that may be underwater until after Thanksgiving?
Yeah, this is "great progress."