Tag Archive for: flood gates

City Gets Favorable Ruling on BCR for Lake Houston Gates Project

During Harvey, 16,000 homes and 3,300 businesses in the Lake Houston Area flooded. Local leaders identified the disparity in release capacities between the Lake Conroe and Lake Houston Dams as one of the contributing factors to the severity of flooding. The floodgates on Lake Conroe can release water 15 times faster than the gates on Lake Houston. So, adding more floodgates to Lake Houston became one of the area’s primary mitigation goals.

New gates would let the City rapidly lower the water level of Lake Houston in advance of a storm to prevent or reduce upstream flooding.

gates for Lake Houston and Conroe
Lake Houston (l) and Lake Conroe gates (r). Conroe release capacity is 15X greater.

While the City of Houston initially obtained a $50 million grant from FEMA to add gates, two problems became apparent. The project cost more than anticipated and the benefits delivered did not justify the cost – at least the way FEMA was initially calculating them. However, a huge hurdle has been cleared.

The City of Houston has finally secured a favorable ruling from FEMA on a benefit-to-cost ratio, according to a press release from Mayor Pro Tem Dave Martin’s office on 12/7/2022. The key was the FEMA administrator’s decision to allow the inclusion of social benefits, for instance, avoidance of disruptions to business, commerce, schools and the area’s tax base. Those brought the BCR up to 2.88, according to Martin.

Hurdle Removed: Project Now Federally Compliant

Earlier this summer, Martin announced challenges related to the Lake Houston Spillway Dam Improvement Project. The City needed to secure a benefit to cost ratio (BCR) between .75 and 1 and had examined multiple alternatives to find a favorable balance between costs and benefits.

Martin, Mayor Sylvester Turner and Chief Recovery Officer Stephen Costello met with the Federal Emergency Management Agency (FEMA) Administrator to discuss the inequities of the Federal BCR formula associated with incorporation of social benefits.

As a result, Martin and Turner have announced that a large hurdle has been removed. The revised draft BCR for the Lake Houston Spillway Dam Improvement Project has been determined to be “federally compliant and is very favorable.”

The change affected the Lake Houston Gates and several other Houston stormwater projects including the massive, new Inwood Forest detention basin.

New BCR Based on Eleven Gates

Atkins, a City of Houston consultant, revised the BCR for an eleven-gate structure. The eleven gates will be built into the existing embankment on the east side of the Lake Houston Spillway Dam.

New gates would be added to the earthen portion of dam in foreground, not spillway at far end as originally planned.

Building the new gate structure in the east embankment removes the high construction risk of modifying the existing gate structure. It also allows continued use of the existing gate structure during construction, and eliminates the need for a coffer dam in the lake, according to Martin.

The new gates would likely align with the original course of the San Jacinto River, the channel on the left.

Cost Quadruples: Additional Funding Sources Now Necessary

The new preliminary cost estimate of $200 million exceeds the City’s original FEMA grant of $48 million.

Martin, Costello, and State Representative Dan Huberty have already met with the Texas House of Representatives Speaker Dade Phelan’s Director of Finance regarding additional funding. They have positioned the project as a “life and safety initiative” that affects the survival of the community and economy of the Lake Houston Area.

Martin has bi-partisan support already lined up for financing. Key partners this legislative session include:

  • Congressman Dan Crenshaw
  • State Senator Brandon Creighton
  • State Senator John Whitmire (who has already announced his intention to run for Houston mayor after Turner retires)
  • Speaker of the Texas House Dade Phelan
  • State Representative & Chair of Appropriations Dr. Greg Bonnen
  • State Representatives Charles Cunningham and Armando Walle.

Martin plans to work with Federal and State partners to ensure the cost of the Lake Houston Spillway Dam Project is fully funded before he leaves office in December 2023.

Said Martin, “Today a significant obstacle has been surpassed as this project moves forward through the financial process.” The new BCR should let federal, state, and local partners work toward fortifying the Lake Houston Area against future storms.

It would be unfair to call this a “start over.” A huge amount of engineering and analysis has gone into the project. However, challenges turned out to be greater than anyone anticipated after Harvey.

The original timetable from 12/16/19 showed the project completed by now. The fact that it is still alive is a tribute to the persistence of Martin, Turner, Costello and others.

Let’s look forward to the benefits, not backwards to the problems. People are working in the right direction. A huge obstacle has been eliminated. We just need to keep tackling new obstacles as they occur. Next step: the House and Senate.

I will post construction plans for the 11 gates and the Atkins’ BCR analysis as soon as the City supplies them; they promised they would.

Posted by Bob Rehak on 12/7/22

1926 Days since Hurricane Harvey

Martin Updates Community on Additional Gates for Lake Houston

Perhaps no flood-mitigation project has generated more interest in the Lake Houston Area recently than the addition of more flood gates to the Lake Houston Dam. In recent months, as engineers worked on the project’s benefit/cost ratio, information about the project became hard to find. That fueled rumors.

But Tuesday night, at the Kingwood Community Center, Mayor Pro Tem Dave Martin put many of those rumors to rest. He denied the project was on hold, reaffirmed the City’s commitment to the project, and outlined the three main issues that engineers are currently grappling with.

Issues Still Being Evaluated

The main issues include:

  • Safety concerns about cutting into the concrete of a dam that’s almost 70 years old.
  • Getting the benefit/cost ratio up.
  • Finding a suitable alternative that significantly reduces flood risk within the budget.

Martin elaborated on each. Regarding:

Safety concerns – He described the risks of cutting into it to install crest gates. Among them, he said engineers worried about structural stability of the dam after construction. Accordingly, they are recommending significant reinforcement of the concrete. He also hinted that contractors might not bid on the project for fear of the potential liability.

Benefit/Cost Ratio – He said that the higher-than-expects costs on of some alternatives drove the BCR down, and that that was driving the exploration of additional alternatives. He did say, however, that FEMA allows including “social benefits” when the BCR is between .75 and 1.0. The inclusion of social benefits still must yield a BCR of 1.0 or greater. On a separate note, a federal employee told me that the Biden administration may change this policy. So significant uncertainty still exists re: calculation of the BCR.

Budget – He implied that some alternatives under consideration became non-starters because of high costs and inflation.

Alternatives Still Under Consideration

So, the search for a suitable alternative that meets all objectives continues. Among the options still in the running, Martin mentioned crest gates on the west side of the dam and adding a tainter gate to the earthen, eastern portion.

Martin shared a timetable that shows construction beginning in November. However, FEMA must approve the benefit/cost ratio before they release construction funds.

Schedule for adding gates to Lake Houston, first shown in July 2021. Also shown on 4/19/2022. Martin emphasized the schedule has not changed, but could.

Background of Project

At the peak of Harvey, 425,000 cubic feet per second (CFS) went over the dam’s spillway. That’s five times the average flow of Niagra Falls. Floodwater backed up so far that it flooded thousands of homes and businesses. It also killed 13 people in the Lake Houston Area, 12 of them in one retirement center.

The release of 80,000 CFS from Lake Conroe contributed almost a fifth of the water going over the spillway. Lake Conroe gates can release 150,000 CFS while Lake Houston’s can release only 10,000 CFS. The disparity in release capacity caused many to ask whether more gates on Lake Houston could reduce flooding.

Martin pointed out that when water gets high enough in Lake Houston, it can escape over a 2,000-foot-wide spillway. However, more gates could play a role in a pre-release strategy.

Pre-releasing water from Lake Houston in advance of major storms, as the City does now, creates extra capacity in the lake so that it can absorb more water without flooding homes and businesses. This strategy (coupled with the seasonal lowering of Lake Conroe) has worked effectively since Harvey and prevented flooding on more than one occasion.

Time Vs. Release Capacity Vs. Water Preservation

However, right now, it takes so long to release water from Lake Houston that storms can sometimes veer away and miss us after the lowering starts. Thus, water could be wasted. But bigger gates would let dam operators release the same volume of water in less time, so operators would not have to start releasing water so far in advance. In other words they would have a higher degree of confidence that the the storm would not veer away and that release was worthwhile.

Martin reassured people that:

  • Smaller (i.e., less costly) floodgates can lower Lake Houston sufficiently if given enough time
  • The lake usually refills quickly
  • Even if it doesn’t, the City can always call for the release of water from Lake Conroe.

We should know within a few months whether Black & Veatch, the engineering company leading the project, has succeeded in designing additional gates within the budget that meet all other objectives.

Staying on the schedule above will be ambitious. FEMA must approve the BCR before releasing money for construction.

Posted by Bob Rehak on April 21, 2022

1696 Days since Hurricane Harvey

Reminder: Floodgate Meeting at Kingwood Community Center on Thursday, July 8

On Thursday, July 8, Mayor Pro Tem Dave Martin will host a pubic meeting to discuss the status of adding more floodgates to the Lake Houston Dam. Preliminary engineering finished earlier this year. In March, the Coastal Water Authority board approved Black & Veatch to begin final engineering.

Need for More Gates

The Lake Houston Area Task Force identified more and higher capacity floodgates as a key element in the area’s flood-mitigation strategy. The current gates have one-fifteenth the capacity of those at the Lake Conroe Dam. That makes it difficult to shed water from Lake Houston before people flood if Lake Conroe opens its gates as it did during Harvey.

During Harvey, Conroe released 79,000 cubic feet per second. That was one third of all the water coming down the West Fork between Humble and Kingwood. All by itself, that 79,000 CFS would have been the ninth largest flood in West Fork history. And that made the difference between flooding and not flooding for thousands of homes and businesses near the lake.

During Harvey, the peak flow over the spillway was five times the average flow over Niagra Falls. A wall of water 11 feet tall cascaded over the spillway above. Enough to fill NRG stadium in 3.5 minutes.

Lake Houston Dam During Harvey. The proposed crest gates would go in the far upper left of the spillway.

Floodgate Meeting Details

See the meeting details below.

Thursday, July 8, 2021
At the Kingwood Community Center (4102 Rustic Woods)
Doors Open 5:30 PM
Dredging Update Starts 5:45 PM
Gate Update Starts at 6 PM

Chief Recovery Officer, Stephen Costello, will provide a very brief update on Lake Houston Dredging operations at 5:45 p.m. before the Spillway Improvement Project program begins.

The program to discuss the Lake Houston Dam Spillway Improvement Project will start at 6:00 p.m. and conclude at 7:45 p.m. But don’t worry about sitting through a 2 hour meeting.

The main presentation by Black & Veatch, the project engineers, will be followed by a short Q&A session. The meeting will then transition into breakout sessions. Breakout tables will let residents engage with project management staff and engineers in small groups to ask more detailed questions.

Project Benefits

The Lake Houston Dam Spillway project will increase the outflow capacity of the Lake Houston Dam. The project proposes installing new crest gates in the existing uncontrolled spillway. This will allow for a rapid decrease of water levels in Lake Houston in advance of storm events to prevent or reduce upstream flooding. Engineers estimate the recommended alternative could help about 35,000 residents and 5,000 structures. It’s important for people to understand that if they flooded from streams or channels far from the lake during Harvey, this may not help them.


A Federal Emergency Management Agency (FEMA) Hazard Mitigation Grant Program provides $4.3 million for engineering and positions the city to receive another $42.7 million for construction.

Posted by Bob Rehak on 7/6/2021 based on info provided by Dave Martin’s Office

1407 Days since Hurricane Harvey