SJRA’s Pre-Release Study Shows No Lake-Houston-Area Benefit

11/6/26 – Approximately three dozen people attended a San Jacinto River Authority (SJRA) presentation last night at Conroe’s Lone Star Convention Center to review the results of a flood-mitigation study on “pre-release.”

Pre-release is the practice of lowering a lake in advance of a storm to create extra room for incoming water, thereby reducing flood risk.

Major Findings

The study found that pre-releasing water from Lake Conroe before major storms provided some measurable flood-risk reduction there. However, it also found no measurable reduction for Lake Houston.

The difficult-to-follow, 53-minute presentation reviewed 17 alternative model runs showing the impact of pre-release under various conditions and assumptions on both Lake Conroe and Lake Houston. See below.

However, all model runs were predicated on the installation of new floodgates which would add 84,000 cubic feet per second (CFS) of release capacity to the Lake Houston Dam.

The modeling showed no benefit to pre-release in the Lake Houston Area … after the addition of new gates.

SJRA Presentation

The purpose of the new gates is to reduce flood risk by enabling pre-releases much closer to storms, thereby eliminating uncertainty related to weather forecasts. The new gates will also help Lake Houston keep up with Lake Conroe releases during storms.

So, the findings are not too surprising, even though the initial shock of the negative findings may alarm people in the Lake Houston Area. Regardless, many questions remain.

Unexplained Contradictions

The presentation was very difficult to understand. Several unexplained contradictions jumped out at me. The presenter made claims that differed from the historical record. For instance, he said:

1. The distance from Lake Conroe to Lake Houston was 45 miles; I measure it at 30 in Google Earth Pro. This could affect the timing of how tributary floodwaters stack on top of each other.
2. We got 24.8 inches of rain from Hurricane Harvey. That’s true at the Lake Conroe Dam. But at Lake Houston, we got 47.4 – almost double.
3. Their models assumed Harvey happened during a drought; it didn’t. A drought would have increased infiltration of rainfall and reduced flooding.
4. They found that Lake Conroe’s discharge accounted for only 12-14% of the inflows into Lake Houston. Data previously released by SJRA showed that during Harvey, Lake Conroe discharges accounted for 33% of the floodwater coming down the West Fork between Humble and Kingwood where most of the damage and deaths occurred. The same SJRA data shows that the peak release from Lake Conroe accounted for approximately 20% of the floodwater going over the Lake Houston Spillway. So percentages previously cited by SJRA were 2-3 times higher than shown in the table above.
5. Inflow to Lake Conroe during Harvey exceeded outflow. That contradicts testimony and data provided by SJRA’s previous flood manager, Chuck Gilman, under oath.
6. “No one can predict a rain event.” “It’s impossible to predict rain events.” Really? Tell that to the National Weather Service and National Hurricane Center.

The SJRA’s engineers may have had explanations for these contradictions. But they failed to provide them or acknowledge any conflict in the meeting.

Ominous Omissions

The study also failed to:

• Model:
  • Actual conditions during Harvey.
  • Impacts to the West Fork between Humble and Kingwood, where most of the damage and deaths occurred during Harvey.
  • The 1994 flood, the previous “flood of record” in the region.
  • Dollar value of homes flooded or removed from floodplain.
  • Loss of tax revenue.
  • Impact on schools, hospitals, transportation, industry, etc.
• Explain:
  • How they modeled the number of structures flooded/not flooded.
  • Why, during Harvey, they released water from Lake Conroe at a rate exceeding inflow when they had three available feet of storage remaining.
  • Terms like “annual water supply.” (However, SJRA did explain it today. SJRA and City of Houston may only divert or take up to a total of 100,000 acre-feet of water per year from Lake Conroe. Pre-releases count against that limit. However, water released during a storm does not.)
• Provide:
  • Before/after maps showing impact of pre-releases vs. gates.
• Assess:
  • The cost of pre-releases vs. more floodgates.

Study Predicated on Having More Floodgates in Place

Many people in the audience were confused by why the SJRA chose to model flood risk AFTER the addition of more floodgates to Lake Houston.

One person called the presentation “A whole bunch of nothing!”

Another, intimately familiar with the gate project, questioned whether additional funding for the gates would be available to make them a reality given the recent election. A $195 million shortfall currently exists between committed funding ($120 million) and estimated construction costs ($315 million).

Yet another person told me that the survey should have shown the impacts of pre-release with and without the gates. “It also should be flexible enough to be modified as dredging happens, the river moves, or to address future development conditions. To not address present conditions and only the situation that ‘may’ be in 5 years was a complete miss by the engineering team and SJRA.”

The SJRA seems to have abandoned a working program and not replaced it. They went from “seasonal lake lowering” to “active storm management” (meaning “pre-release if needed”).

Now, they’re betting big on the addition of new gates to the Lake Houston Dam. But those are almost $200 million and five years away…IF we can find the money.

In the meantime, it’s unclear how this study affects current pre-release policy or decisions. SJRA did not discuss that.

To see their entire slide presentation, click here. The Texas Water Development Board, City of Houston, and City of Humble partnered with SJRA on the project.

Posted by Bob Rehak on 11/6/26

3356 Days since Hurricane Harvey