Hays County Soil And Water Conservation District Tour Upper San Marcos Watershed Dams

Hays County Soil and Water Conservation District

On Wednesday, May 1, the Upper San Marcos Flood Control and Reclamation District and the Hays County Soil and Water Conservation Board hosted officials and staff from local organizations and authorities to tour the Upper San Marcos River watershed and flood control sites.

Officials and staff from the City of San Marcos, Hays County, Texas State University’s Environmental Health, Safety and Risk Management Department, the Edward’s Aquifer Authority, the Natural Resources Conservation Service and the Texas State Soil and Water Conservation Board were given a first-hand look at the five dams located throughout the bodies of water that feed into the San Marcos River.

The tour opened with introductions by Hays County SWCD Secretary and Treasurer, Cliff Caskey, who thanked everyone for being in attendance.

Bill Taylor, manager of the Upper San Marcos Watershed District, discussed the history of the dams and flooding in San Marcos.

Taylor stated on May 15, 1970, the area experienced catastrophic flooding, where record rainfall fell within 30 hours and flooded the Blanco River, Sink Spring Creek and Purgatory Creek; floodwaters placed most of the city underwater and caused the deaths of two residents.

The 1970 flood spurred action amongst residents and elected officials. Taylor said, through cooperative efforts of state and federal governments, city and county officials and the Upper San Marcos Watershed and Flood Control District was formed.

The flood prevention dams were built between 1981 and 1991 to help improve the stream channels on Purgatory and Willow Springs Creeks to reduce flood waters from entering the City of San Marcos during heavy rainfall events.

According to Hays County SWCD, The Upper San Marcos Watershed District, the Hays County SWCD, Hays County Commissioners and staff, the City of San Marcos staff and the Natural Resources Conservation Service (NCRS) work in cooperation in the responsibility and upkeep of the dams to ensure their ability to reduce floods and provide re-charge benefits to the Edward’s Aquifer.

Taylor explained that congressman James Jarrell “Jake” Pickle came to San Marcos to survey the damage from the flood of 1970 and was instrumental in securing the federal funding that helped enable the dams to be built around San Marcos.

“In Congressman Pickle’s testimony to the Congressional Appropriations Committee, he testified that the flood control structures would potentially eliminate 95 percent of the flooding problems in San Marcos,” according to Taylor.

There have been several subsequent floods after the flood of 1970.  So far, the dams have help up, even through the flood of 1998, 2002, and the most recent flood in October 2015. 

Hays County Natural Resources Conservation Service’s, District Conservationist, Kathryn Brady, explained that even though the city still sees some impacts from flooding, on the streets, highways and in neighborhoods and houses these dams still protect the city; without them, the flooding could completely devastate the community. 

Brady said most people don’t even know that five dams exist along the creeks that feed into the San Marcos River; much less the important role that they play in protecting the city, roads, bridges and re-charging the aquifer.

NRCS state engineer, Todd Marek said, “These five strictures provide at least $3.7 million in annual benefits including the reduction in flood damages to agricultural lands, rural and urban infrastructure not to mention preventing a devastating loss of life.  There is more than 20, 352 acre-feet or more than 6.6 billion gallons of water that would have ravaged the city in the October 2015 flood, if not for the dams.”

Marek explained how the structures work; when heavy rainfall events occur, the dams are designed to capture raging flood waters and hold it, releasing it slowly downstream. Each dam has a principal spillway that releases water through the dam at a controlled rate into the auxiliary or emergency spillway which is designed to keep floods from topping the dam and washing it out.

Hays County Assistant Emergency Management Specialist, Justin McInnis, discussed the flood event in October 2015 and the repairs done after the flood event. 

The repairs help to mitigate erosion caused by the flood waters and work to slow down the water in the auxiliary spillway as it enters the waterway toward the creeks and springs, McInnis said.

To complete the repairs NRCS allocated $8 million from their Emergency Watershed Program funds. Flood gauges were also installed. 

Colleen Cook of Texas State’s Environmental Health Safety and Risk Management Department said, “You don’t realize how incredible these structures are until you’re up close and personal with them.  These flood control structures and those involved in maintaining the structures are the unsung heroes of this community, quietly ensuring San Marcos isn’t washed away during a big event. It’s amazing how much water these structures hold back, and I’m sure the community members cannot truly grasp their impact.”