Tag Archive for: Lake Conroe release

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.

From “A Brief History of Lake Houston and the Hurricane Harvey Flood,” by Tim Garfield and RD Kissling with help from Bob Rehak, 2019.

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.)

Significantly, Garfield says, these gauges all showed flattening flow-rate curves before the release ramp up. Those curves then turned and steepened upward as the Conroe release pulse arrived at those gauges.

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.

Residents trying to escape as Harvey's floodwaters rose
Kingwood Village Estates residents trying to escape as Harvey’s floodwaters rose. Twelve later died.

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.
More than 4,400 structures flooded in Humble and Kingwood along the West Fork. Source: HCFCD.

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

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.

Editorial: Endorsing Turner Compromise on Lake Lowering, Adding One Thing

Tonight, the SJRA board will decide whether to continue the temporary seasonal lake lowering policy until other flood mitigation measures can be put in place. Last night, Houston Mayor Sylvester Turner proposed a compromise. Instead of lowering Lake Conroe to 199 feet in the fall, he suggests lowering it to 199.5, but would lower it the other half foot five days in advance of any predicted tropical storm.

Comparing Proposal to Historical Averages

SJRA data shows that 199.5 is within 1.5 to 4 inches of the historical averages for affected months.

From presentation by SJRA’s Chuck Gilman at last board meeting.

If Lake Conroe residents can’t live with that, then they should complain to Mother Nature. The difference will be barely perceptible.

But the ability to lower the lake further five days in advance of a tropical storm still provides downstream residents with safety. Five days should be enough time to get water into the Gulf of Mexico.

The extra storage capacity created in the lake should help protect Conroe residents as well as those downstream by:

  • Delaying the need to release floodwater
  • Giving peaks on other tributaries time to pass through the watershed
  • Reducing the width and peak of floodwaters downstream
  • Giving the SJRA more time to issue evacuation warnings if necessary
  • Giving downstream residents more time to evacuate and move cars and other valuables to higher ground

A few inches seems like a good compromise that may be best for everyone involved.

One Additional Recommendation

However, I would add one other thing to the request. During releases, I would urge the SJRA to hold back as much water as possible as long as possible.

Instead of returning the lake to normal as soon as possible, keep it as high as possible without jeopardizing safety. Make that a gate operation policy.

This should give peaks on other watersheds time to pass through Lake Houston before releases from Lake Conroe add to them.

Respectfully submitted by Bob Rehak on 2/20/2020

905 Days after Hurricane Harvey

By Itself, Lake Conroe Discharge During Harvey Among Top Ten West Fork Floods of All Time

The roughly 80,000 cubic feet per second (CFS) Lake Conroe discharged at the peak of Harvey would have created the ninth largest flood in West Fork History – all by itself. Only eight floods ever had higher “discharge” rates AND those all included floodwaters from other tributaries, such as Lake Creek, Spring Creek, Cypress Creek and numerous drainage ditches.

Discharge is the volume of water flowing past a point on a stream. Discharge from a dam would be the volume flowing past the gates.

The discharge during Harvey is important because residents fighting the seasonal lowering of Lake Conroe claim the impact of the release on Humble and Kingwood was insignificant.

Question I Asked Flood Control

So I asked Jeff Lindner, Harris County Flood Control meteorologist, this simple question. “Assuming not a drop of rain fell in any other of the West Fork tributaries, where would that 80,000 CFS have ranked among the history of West Fork floods?” I then asked him to base his analysis on the West Fork gage at US59. It combines water from ALL upstream West Fork tributaries. It’s also the closest gage in continuous operation to the highly populated Humble/Kingwood corridor. That’s where the vast majority of Lake Houston Area damage occurred during Harvey.

Only eight floods have ever exceeded 80,000 CFS at US59.

They occurred on:

  • 8/28/17 (Harvey)
  • 10/18/94 (Previous Record Flood)
  • 11/26/40
  • 5/31/29
  • 5/29/16 (Memorial Day)
  • 11/15/98
  • 5/7/35
  • 4/21/16 (Tax Day)

Note: three of these events happened before the construction of Lake Conroe in 1973. All since the advent of Lake Conroe flooded West Fork structures.

One Statistic Addresses Host of Issues

This observation (ninth largest flood by itself) addresses a host of issues raised by Lake Conroe people about lowering the lake seasonally to create a buffer against downstream flooding. They contend that:

  • In the grand scheme of things, the Lake Conroe release during Harvey had an insignificant impact on flooding in the Humble/Kingwood area.
  • Kingwood always floods.
  • Imelda proves that Kingwood will flood even when Conroe is not releasing water.
  • There’s no need to create extra storage capacity to offset future floods.

What Records Really Show

On the contrary:

Will Two Feet Matter?

Lowering Lake Conroe two feet in advance of another Harvey will probably not make much of a difference. Likewise, lowering it two feet in advance of 1-inch rain would be unnecessary. The real value happens somewhere between those extremes in a 10-, 25-, 50- or perhaps even a 100-year storm. Somewhere along that spectrum, we will get enough rain to perhaps flood homes, but we’ll also have enough extra lake capacity to avoid actually flooding them.

We just don’t know where that point is right now. Jing Chen, the engineer with Harris County Flood Control managing the San Jacinto River Basin Study says that project will not be far enough along to model those scenarios until August of this year.

However, the SJRA feels the lower lake levels did help avoid flooding between Humble and Kingwood in May of last year. I concur. It’s also possible that the two foot lowering might create enough of a buffer to have avoided flooding many homes along the West Fork during the Tax and Memorial Day floods in 2016. Perhaps it wouldn’t have saved them all. But it might have avoided flooding many at the periphery of a flood.

Increasing Upstream Detention Capacity: A Proven Flood Mitigation Strategy

According to Matt Zeve, Deputy Executive Director of Harris County Flood Control, holding water upstream is a proven flood mitigation strategy. Engineers in the Houston area created upstream detention more than 80 years ago with the Barker and Addicks reservoirs. Braes Bayou now has five different detention areas; White Oak Bayou has five with another under construction.

Such detention areas collect water during a storm and then release it slowly after a flood passes.

The extra storage capacity created by lowering Lake Conroe 1-2 feet works the same way. The idea: to reduce the amount and/or rate of water released during a flood to help avoid downstream property damage.

SJRA Mission and Lake Conroe History Includes Flood Prevention

The enabling legislation of the SJRA mentions flood prevention three times. Moreover, the area now occupied by Lake Conroe was considered for floodwater detention as early as 1957, as this Master Plan for the SJRA that year shows – i.e., on the map below. Many of these proposed lakes/reservoirs serve a dual purpose according to Zeve. They help prevent floods AND supply water.

Page 29 of SJRA Master Plan from 1957

This map puts to rest another rumor spread by the Lake Conroe Association. They claim Lake Conroe was never conceived as a flood control reservoir; it is strictly a water supply reservoir. See the discussion of flood control starting on page 16 of the 1957 Master Plan. Then on page 27, see Exhibit A.

It shows the SJRA considered building 20 dams that year.

So far it has built only one: Lake Conroe.

Therefore, Lake Conroe is currently the only way we have to mitigate flooding until we put other mitigation measures in place.

Posted by Bob Rehak on 1/23/2020

877 Days since Hurricane Harvey

Note: A reader’s question on Facebook prompted this post. But I can’t find his name now. My apologies. No offense intended.

Childhood Terror From Harvey: Ulrich Family’s Experience and Letter to SJRA Board

Colleen Ulrich gave me permission to share her family’s Hurricane Harvey experience. She captured the terror in this letter to the San Jacinto River Authority Board. It supports the continued seasonal lowering of Lake Conroe to provide a buffer against flooding until other mitigation measures can be put in place. Her home did not flood UNTIL AFTER the Lake Conroe release.

Full Text of Ulrich Letter

Dear SJRA Board Members,

The purpose of my email is to petition all SRJA Board Members to approve the temporary, seasonal lowering of Lake Conroe for 2020.
As an introduction, I have been a resident of Kingwood since August 2005 when I evacuated from New Orleans due to Hurricane Katrina. We never moved back because our family fell in love with our adopted state of Texas and our adopted home town of Kingwood. I live in the Barrington neighborhood with my husband and 10-year-old daughter. Our home was flooded with 2 feet 2 inches of water in August 2017. 

Colleen Ulrich’s vehicle during Hurricane Harvey after Lake Conroe release. This photo and those below courtesy of Colleen Ulrich. All used with permission.

 Childhood Memories

One of the issues that those opposed to the temporary, seasonal lowering of Lake Conroe is that they feel deprived of their ability to enjoy the lake and to create fun summer time boating memories for their families and children. As a mother and Kingwood resident, I am petitioning you to vote in favor of the temporary, seasonal lowering of Lake Conroe to ensure the safety of my child and all of the children of Kingwood and to ensure none of the Kingwood area children have any memories similar to the ones that were created from the flood in August 2017. 

Colleen Ulrich’s dining room during Hurricane Harvey after the SJRA opened the flood gates on Lake Conroe.

Our daughter, Alexandra, was 7 1/2 at the time and her memories include sitting on our stairwell alone in our home while my husband carried me on his back to be evacuated by boat because the quickly rising water was too high and the current too strong for me to walk by myself. Alexandra’s memories include riding in that same boat out of our neighborhood and seeing the houses with up to 4 feet of water in them. Alexandra’s memories include having her childhood bedroom destroyed by floodwaters.

I promise you that these memories will never fade for her.

The Ulrich living room after the Lake Conroe release during Harvey.

Fun Vs. Safety

So I petition to the Board, what is more important – creating fleeting childhood memories of a boat ride in the summer on Lake Conroe or averting traumatic childhood memories of a flood? 

What is more important – the perceived Lake Conroe falling property values or the safety of our children and residents?

Heirlooms underwater.

I am in agreement that the lowering of Lake Conroe and Lake Houston are both temporary solutions. And of course these temporary solutions should be revisited once all of the other permanent measures including the installation of additional gates in Lake Houston are put in place. But until that time, I pray that you will make the right decision and keep the temporary, seasonal lowering in place until permanent measures can ensure the safety of all the children and of all the residents of Kingwood and the surrounding areas.  

Ulrich kitchen, cabinets and appliances destroyed.
The piano that’s not so grand since Harvey.

Video of Evac

For your consideration, my husband recorded this video and posted it on YouTube so we can remind others of the trauma of that day.  This was his boat ride out of Barrington.

I appreciate your service to our community and your consideration of my appeal to approve the lowering of Lake Conroe.


Colleen Ulrich

Address and Phone Number Withheld for Purposes of This Post

Tell the SJRA Board about your Harvey experience and why you would like to see them continue lowering Lake Conroe seasonally until other flood mitigation measures can be put in place. Come to the next board meeting and tell them in person or write them by visiting https://www.sjra.net/about/board/. Scroll down to the bottom of the page to see the email form.

Posted by Bob Rehak on 1/18/2020

872 Days after Hurricane Harvey

Surprise in Final Harvey Report

Yesterday, I published on this website the 32-page Final Hurricane Harvey Flood Report from Harris County Flood Control. Today someone asked me, “What was the biggest surprise in it?”  Talk about pressure! Harris County packed lots of meat into those 32 pages! I pondered the question all morning and connected the following dots.

Five Times the Average Flow of Niagra Falls

For me, the biggest surprises were the volume of water going over the Lake Houston Dam and where it came from. At the peak of the storm, the amount of water going over the dam exceeded the volume ofNiagra Falls on an average day by 5X. The final figures actually show more water than previously thought going over the spillway: 491,800 cubic feet per second (cfs) vs. 450,000 cfs previously estimated, an increase of almost 10 percent.

More Flow From East Fork than West

When you look at where all that water came from, there was another surprise. More came from the East Fork than the West! See page 12.

In the East Fork numbers, include Peach Creek, Caney Creek and Luce Bayou; In the West Fork numbers, include Spring Creek and Cypress Creek.

One Third of West Fork Flow Came From Lake Conroe Dam Release

Roughly 240,000 cfs came down the West Fork. Seventy-nine thousand cfs came from the release at the Lake Conroe Dam, according to SJRA estimates. So ONE THIRD of the water coming down the West Fork at its peak was from the release. That’s important for the following reason.

Previously, SJRA indicated the Conroe release was approximately 15 percent of all the water going into Lake Houston. While technically true, this observation clouds the picture of what happened on the West Fork. The West Fork sustained 2.5x more damage than the East Fork and the main body of the lake COMBINED. (See Page 14). Survivor interviews suggest that much of that damage did not happen until the release from Lake Conroe!

Conclusion: Multiple Mitigation Measures Needed

That extra 79,000 cfs underscores the need to:

  • Temporarily lower the level of Lake Conroe during the peak of hurricane season
  • Enhance the carrying capacity and velocity of the West Fork through dredging
  • Add upstream retention that helps offset Lake Conroe releases
  • Add flood gates to Lake Houston.

The last item would increase the release rate of the Lake Houston dam during a major storm. The additional discharge capacity of the ten gates proposed by Mayor Turner could easily equal the 80,000 cfs discharged from Lake Conroe, eliminating a bottleneck on the river.

Of course, if we get another Harvey, many people will flood. No surprise there. But these measures should help reduce the damage, and perhaps eliminate it when we have smaller events, such as the Tax and Memorial Day Floods of 2015 and 2016.

Posted 6/5/2018 by Bob Rehak

280 Days since Hurricane Harvey