Update on Lake Houston Gates

5/25/24 – Houston City Council Members Fred Flickinger and Twila Carter met at the Lake Houston gates yesterday with members of the Coastal Water Authority (CWA), Black & Veatch engineering, and Houston Public Works. They reviewed the status of repairs to a broken gate and a program to add 11 new gates to the dam.

*Meeting at Lake Houston gates on 5/24/24 to discuss broken gate and 11 new gates.*

Broken Gate Stuck in Down, Not Up Position

During the early May floods of 2024, news of a broken gate on the Lake Houston Dam spread rapidly on social media. Flooding concerns fueled rumors. Some folks heard the gate was stuck in the closed position. Others heard it was open. A visit to the gates yesterday confirmed that it was stuck in the down position.

A CWA employee said that one of two chains used to raise and lower the gate broke. That raised the possibility of the gate becoming jammed sideways in its frame if they tried to raise it with the remaining chain attached only to one side. If the gate did jam, CWA would have no ability to re-lower it.

That, in turn, meant the lake would continue losing water after the flood subsided. So they opted to leave it closed during the flood.

Gate *stuck in down position* *has only one chain.* *I could not safely get a camera angle that showed the area of missing chain.*

*Winch used to raise/lower tainter gates.*

*Tainter gates (left) rotate via radial arms. Two gates on right raise/lower from bottom hinge.* *(Picture taken last year. Only one tainter gate was releasing yesterday.)*

The Lake Houston Dam also has a 3160 foot wide spillway in addition to the four gates.

*As of yesterday afternoon, water* *was no longer going over the spillway*, *but Lake Houston was filled to max.*

*However, operators* *were still releasing water through working tainter gate* *to reduce the lake level* *for repairs.*

*The chain on one side of this gate was pulling it up unevenly*.

Repairs to Begin Next Week

The Coastal Water Authority (CWA) plans to fix the broken tainter-gate chain next week when the water level in the lake is lower. CWA manages Lake Houston for the City.

The repair team will include divers who will re-attach the broken chain to the upstream side of the gate underwater.

The operation was too dangerous to attempt during the flood because other gates were open. And at the peak of the flood, water going over the 3160-foot-wide spillway was SIX feet high.

Divers could have easily been swept away by the strong currents. One cubic foot of fresh water weighs about 62 pounds. And at the height of the flood, more than 100,000 cubic feet per second were flowing over the spillway and through the dam’s gates. That’s a lot of force!

Current Lake Houston Gates Have Limited Capacity

The current Lake Houston gates have a combined release capacity of only 10,000 cubic feet per second (CFS) – about 2,500 CFS each.

They are useful in pre-release scenarios, i.e., releasing water before a storm to create extra storage capacity in the lake for stormwater. That can reduce flood peaks both up- and downstream from the dam.

However, the current Lake Houston gates are so small, that it can take days to lower the lake significantly. And during that time, storms can veer away. Meteorologists just cannot offer precise estimates about where a storm will hit that far in advance.

Status of New, Bigger Gates

Adding more and bigger gates to the dam could reduce the lead time necessary to lower the lake. And that would give dam operators more certainty that they aren’t wasting the water.

To release water faster, before and during a storm, the City of Houston plans to add 11 more Lake Houston gates to the earthen portion of the dam just east of the old gates.

The new gates could release a total of 80,000 CFS, bringing the total pre-release capacity up to 90,000 CFS – 9X higher than the current rate.

*New gates would be installed to right of existing gates in sunny area.*

When complete, the CWA will be able to pre-release as much water in 2-3 hours as it currently does in a day.

The extra storage capacity for stormwater in the lake could then help reduce flood peaks both up- and downstream.

Extra Lake Houston gates could also release water faster during a storm.

According to the CWA, studies show that the extra gates would not worsen downstream flooding. Homes have already been bought out in downstream areas that would be affected.

The City is currently in the design phase for the new gate structure. Construction should start sometime in 2025 according to Council Member Flickinger.

However, the new gates would have to be custom manufactured. No one offers gates that size as off-the-shelf items. So, supply-chain staffing shortages could delay delivery of the gates. Reportedly, the companies that manufacture gates are still being affected by staffing shortages that started during the Covid pandemic.

Multiple Benefits of More Lake Houston Gates

When complete, the 90,000 CFS release capacity of the 15 Lake Houston gates (4 old, 11 new) would exceed the largest release ever made by the SJRA from Lake Conroe – 79,000 CFS during Hurricane Harvey.

That would help improve joint operations of the two lakes during flood events.

But engineers at yesterday’s meeting cautioned that the new gates are not a silver bullet.

They say pre-release won’t be needed during small floods. And pre-release will have minimal impact during giant floods, such as Harvey.

That’s because large events like Harvey can replace the entire volume of the lake dozens of times during the event. In such floods, lowering the lake a foot or two beforehand will provide negligible benefits. Another monster flood could replace that volume in minutes.

However, the gates will provide significant improvements during 25-, 50- and 75-year flood events. That will provide greater safety margins for many people who previously flooded or were on the verge of flooding during such events.

Posted by Bob Rehak on 5/25/24

2461 Days since Hurricane Harvey