What Happened Downstream During Harvey as Lake Conroe Released 79,000 CFS
Last night, I posted some statistics about Lake Conroe levels after the SJRA started the release during Hurricane Harvey. Tim Garfield and R.D. Kissling, two top geologists, now retired from one of the world’s largest oil companies, have looked at the release from a downstream perspective. Last year, they put everything they learned into this 69-page presentation delivered to the University of Houston Honors Program.
Recap of Key Points About Lake Conroe Release
To recap several key points:
- The SJRA never did let Lake Conroe rise to its allowable flowage easement. The water level in Lake Conroe peaked at 7 a.m., August 28, 2017, at 206.23 feet. The SJRA’s flowage easement is 207 feet.
- Outflow exceeded inflow by 8:30 a.m. on the 28th and stayed that way for the duration of the storm. As the lake level declined, the lake had up to 3 available feet of storage capacity.
- Yet the SJRA kept releasing, on average, 2X – 10X more water than it was taking in. At one point, the ratio exceeded 100:1.
Tracking the Release Down West Fork
Garfield notes that the discharge ramp up that began the evening of the 27th reached a peak discharge rate of more than 79,000 cubic feet per second (cfs) just before noon on the 28th. The discharge rate didn’t dip below 70,000 cfs until 4 a.m. on the 29th – more than 16 hours later.
Following in lockstep with the Conroe release, flow rates at downstream gauges ramped up, in lockstep. By lining up the peaks of gages downriver, you can literally see the water surging down the West Fork all the way to Lake Houston. (See left side of image above.)
Timing and Impact of Release in Lake Houston Area
Peak flow at the Humble gauge was reached shortly after noon on the 29th, roughly 24 hours after peak discharge was reached at the dam and roughly 30 hours after the high-rate release ramp up began.
Water started creeping under the doors of Kingwood Village Estates, a senior living center in Kingwood Town Center about 1.4 miles from the West Fork, at 3 a.m., on August 29th, 2017. It kept rising all morning and finally stopped another mile further inland. Water entered the last (highest) house to flood in Kings Point (the Kingwood subdivision closest to the main body of Lake Houston) at 2 p.m. that same day, according to Elise Whitney Bishop.
The level of upper Lake Houston, as measured at US59, rose an additional 7 feet during this period.
Significant additional flooding of Kingwood homes can be tied to this same period of increased discharge.
Flow rates measured at the Grand Parkway gauge and calculated at the Humble gage indicate a flow rate increase in this period of between 70,000 to 80,000 cfs, corresponding closely to the 79,000+ peak flow rate added by the Conroe dam discharge.
“The data from the affidavits further supports several key conclusions from the Harvey Flood Fundamentals section of our University of Houston talk,” said Garfield. Those include:
- The large sustained release from Lake Conroe made West Fork flooding worse. The extra 80,000 cfs increased the West Fork flow 50%.
- The release occurred as the storm was abating. It significantly increased flood damage in the Lake Houston area.
The list of damages ran well over a billion dollars.
The SJRA Argument
The SJRA maintains to this day that Lake Conroe is a water-supply reservoir, not a flood-control reservoir. See the affidavits of Hector Olmos and Chuck Gilman. Olmos is a consultant who helped design the operations manual for the gates at Lake Conroe. Gilman is the SJRA’s Director of Flood Management, hired the year after Harvey.
They are basically claiming, “We don’t have the right tool to prevent downstream flooding.”
Editorial opinion: That excuse has always sounded hollow to me. It attempts to curtail discussion of whether the SJRA waited too long to start releasing water, released too much at the peak, and then kept on releasing too much for days.
That discussion is a matter of public concern that could save lives and property in the future. We need to have it.
Sadly, it will take the courts to figure this out. In the meantime, the SJRA has hired some of the highest priced lawyers in the country and now appears to be angling for legislative immunity by hinting at higher water prices “statewide” if liability can’t be controlled.
It all smacks of similar arguments in other industries. If you’ve lived long enough, you’ve heard them all before, such as car companies that would be driven out of business if forced to install seat belts and other safety features. Well, that prediction didn’t quite work out! Luckily, for General Motors, the addition of safety features helped fuel its resurgence.
Posted by Bob Rehak on 6/12/2020 with thanks to Tim Garfield and RD Kissling
1018 Days after Hurricane Harvey
The thoughts expressed in this post represent opinions on matters of public concern and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.