Initial options that the City of Houston explored for adding more flood gates to the Lake Houston Dam struggled to achieve a high enough Benefit/Cost Ratio. However, all parties involved are still hopeful that a solution can be found. They are now evaluating yet another option. It would add gates in the earthen (eastern) portion of the dam.
More Gates Would Create More Room For Floodwaters
Flooding devasted the entire Lake Houston Area during Harvey. Since then, Mayor Pro Tem Dave Martin has led an effort to find a way to lower the lake faster in advance of a storm. This would create extra room in the lake for floodwaters. And that would reduce the risk of flooding homes and businesses around it.
Currently, the dam has a fixed height spillway. That makes releasing water in advance of a storm difficult. The dam does have several small gates, but they have only 1/15th the release capacity of the gates on Lake Conroe. Adding more gates would help release water faster…to keep up with water coming downstream.
It would also let managers wait to start a release until they were certain a storm would not veer away. That would help avoid wasting water if forecasts are not accurate.
The Dual-Role Dilemma
The City built Lake Houston in 1953 to supply water. Making the dam play two roles – water supply and flood mitigation – poses a challenge.
In 2017, immediately after Hurricane Harvey, Martin began leading the effort to transform the dam to play a dual role. This would let Lake Houston provide our region with needed drinking water and reduce flood risk.
New Timeline Longer Than Hoped, But Still Shorter Than Usual
A project of this magnitude normally takes up to twelve years. However, Martin worked with federal, state, and local officials to shorten the timeline. Martin now hopes the project will take no longer than seven years. While acknowledging that he hoped completion would happen in as little as five years, Martin also cites unexpected technical and cost challenges related to the aging dam.
Difficulty of Finding Best Alternative
The age of the Lake Houston Spillway, built in 1953, has proven to be a bigger obstacle than expected. Engineers initially proposed six different alternatives for adding different types of gates in different locations, with variations on several.
During that process, engineers discovered hidden challenges with some options that initially looked promising. At this point, they have determined that all six initial options cost more than the federally funded amount of $48 million.
A Complicated Path Forward
So now engineers are focusing on finding the optimal solution while Martin and others explore options to pay for it.
Martin says the City of Houston, Texas Division of Emergency Management and Federal Emergency Management Agency are working together to find the option with the highest Benefit to Cost Ratio (BCR).
Acceptable BCRs for projects like this range from .75 to 1, according to Martin. Preliminary engineering studies found that two crest-gate alternatives (already evaluated) yielded only .48 – largely due to the aging structure of the existing spillway, which drove up costs.
City Expects Answer on Latest Option Before October
Currently, the City has paused the final-design phase of the project while engineers evaluate Alternative 1A. That now consists of five new tainter-gates (not six or twelve as previously reported) on the earthen embankment east of the spillway.
The comprehensive, final BCR analysis for the embankment alternative should be completed by the end of September 2022. The preliminary engineering report suggested the 1A alternative could reduce flood heights by half a foot for a cost of $47.3 million with a BCR of .89. So initially, on the surface, this appears feasible.
Martin Widens Search for Funding
While engineers work to find the best BCR, Martin is leading an effort with BOTH state and federal partners to find additional funding for the project.
For instance, Martin is working with outgoing State Representative Dan Huberty and incoming State Representative Charles Cunningham to seek funds in the upcoming Texas Legislative Session. Martin says that state dollars do not require BCRs like federal dollars do.
While all the challenges would have discouraged many, Martin says they have fortified his resolve. He vows to find a path forward. Martin promises an update in his regular fall public meeting in October and hopes to have an attractive BCR for alternative 1A.
Interim Flood-Mitigation Measures Still In Place
In the meantime, the City of Houston will continue its existing Lake Houston pre-release strategy. It calls for lowering the lake when forecasters predict three or more inches of rain in the San Jacinto Watershed. Since Hurricane Harvey, the City has lowered the lake more than twenty times and successfully avoided flooding.
Thanks to Key Contributors
Martin acknowledges the continuing contributions of Congressman Dan Crenshaw, Governor Greg Abbott, Lt. Governor Dan Patrick, Commissioner Tom Ramsey, State Representative Dan Huberty, State Representative-Elect Charles Cunningham, TDEM-Chief Nim Kidd, Mayor Sylvester Turner, Chief Recovery Officer Stephen Costello, and Harris County Flood Control District.
Martin says, “All parties are committed to constructing these additional gates to help ensure protection against future flood events.”
Posted by Bob Rehak on 8/4/2022
1801 Days since Hurricane Harvey