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A report examining the June flooding that killed 13 people in San Antonio was released to the city council on Thursday. It highlights the velocity of floodwaters reaching eight feet per second and more than two feet high in some places.
The report referred to the June 12 flooding as a "25-year flood," or having a 4% chance of happening in a given year. In the early morning hours, rainfall rates reached upwards of six inches per hour—the worst of which was seen at Beitel Creek near Perrin Beitel Road, Loop 410 and Austin Highway. That's where trapped cars were swept into the creek, killing 11 people. Two more were killed in other parts of San Antonio.
The city hired Kleinfelder, an engineering and design firm, to assess what caused the flooding and what changes needed to be made. Kleinfelder project manager Justin Murray told the council intense bursts of heavy rain combined with dense vegetation led to the unpredictability.
“The best available modeling prior to the event did not accurately depict the depth and velocity on loop 410 on June 12, and the single biggest factor to why what occurred was related to the dense vegetation just north of the frontage road the loop 410 sag point, which is the low point that has been there since 1979 is vulnerable to overtopping, not just in a 25 year event, but also a 10-year event,” Murray said adding that that construction from the Texas Department of Transportation was not a factor.
According to the report, "vehicles entering the [west bound frontage road] during the early stages of flooding but unable to cross the sag point were effectively trapped, with no alternate escape routes available."
A 13-square-mile portion of the watershed that begins around Loop 1604 and ends around Loop 410 and Austin Highway was analyzed.
The recommendations include:
1. Install staff gauges and warning signs with flashing lights and safe detour options
2. Work with TxDOT to develop a plan to protect the westbound frontage road of Loop 410 from high-risk inundation.
3. Review and enhance emergency response protocols between SAPD, SAFD, Public Works, TxDOT, and TransGuide to trigger automatic road closures and public alerts.
4. Relocate gauges to the downstream faces of crossings
5. Expand sensor networks
6. Update existing flood models with current land use and new vegetation
7. Clarify maintenance responsibilities for drainage easements and rights-of-way. Identify maintenance requirements within vegetated areas and prioritize maintenance within flood-prone areas.
The report added that “Placement of the signage should be studied to prevent a 'dead end' where there are no alternate routes to evacuate the area.”
The city also plans to close a crossing at Vicar Road and Perrin Beitel. The lowest point of this roadway sits below Perrin Beitel. “There's another way to access those businesses, and so we're going to eliminate a low water crossing that was a part of this over the next year,” said Assistant City Manager John Peterek.
Peterek told the council that some of the recommended improvements are already underway— like adding staff gauges and flashing warning lights at Austin Highway and the sag point at Loop 410. The city has also created a PSA to show residents how to turn on emergency alerts on mobile devices.
San Antonio Mayor Gina Ortiz Jones has highlighted the state’s flood plan has 14 projects in San Antonio that are currently scoped out at an estimated cost of $411 million. While it’s not clear if the Beitel Creek watershed is in that, Jones said it’s going to take a significant number of financial resources to address the overall flooding issues in the city.
“This is not something that we're going to be able to fund internally ourselves. It's going to be really important that we continue to work with our state delegation and our federal delegation to ensure we have sufficient resources for these major projects,” Jones said.
