Canyon Lake Gorge, outside of New Braunfels, opens a wide crevice along the Balcones Fault, exposing layers of an ancient seabed. Unlike most gorges, this gash in the earth’s surface was created in a matter of weeks, instead of by centuries of gradual erosion.
Open to the public by tours only, the deep cut in the land began on a hot, clear July 4, 2002. In the upper Guadalupe River basin, heavy rains were filling the creeks around Kerrville that were feeding the river. It had been an unusually wet spring, and things were shaping up to become downright soggy.
Canyon Lake was formed by impounding the Guadalupe River. After the dam was finished in 1964, it took three years to fill the pool. The reservoir’s primary purpose is flood control, says Cinde Thomas-Jimenez, education coordinator with the Guadalupe-Blanco River Authority. The lake also provides residents between Austin and San Antonio with drinking water. For nearly 40 years, the U.S. Army Corps of Engineers-managed dam did an admirable job of protecting lives and property downstream.
The 974-foot earthen dam was placed at a choke point at the Balcones Fault where the Guadalupe River funnels out of West Texas and begins the slow drop to the Gulf of Mexico. Because of the Hill County terrain, the Guadalupe River is considered one of the most flash-flood-prone rivers in the world.
The design of the dam included a 943-foot-tall spillway to act as a safety valve. The ideal elevation of the lake is 909 feet above sea level. The river flow below the lake is regulated by a 10-foot-diameter tunnel at the base of the dam that normally releases 350 to 500 cubic feet per second of water into the state’s most popular river recreation area.
Mother Nature had been active in the months leading up to July 2002. Four years of abnormally wet weather had contributed to severe flooding along the Guadalupe River on the coastal plains in the spring of 2002. During the last week of June 2002, the upper river basin was pounded with 35 inches of rain. The area normally receives 30 to 35 inches in a year.
By July 4, the Corps of Engineers at Canyon Lake was bracing for the worst. All of the parks on the lake were evacuated, and water was being released judiciously from the lake to protect the already soaked lower river basin. Despite their best efforts, “the lake level came up fast and furious,” Thomas-Jimenez says.
For the first time in the reservoir’s 38-year history, water breached the spillway. It began as a trickle but reached a depth of 8 feet and 67,000 cubic feet per second over the spillway. During the next six weeks, enough water rushed through the safety valve to fill the lake 31/2 times over.
When the floodwaters finally receded and officials could access the damage, they found a 21/2-mile gorge scoured clean from the dam to where the new channel met the river. The force of the water had removed two hills below the spillway and every bit of vegetation in its way. Boulders the size of houses were tossed around like marbles. The bedrock was exposed along the fault line to more than 40 feet deep in places exposing fossils, dinosaur tracks, and layers of limestone. Imagine the water over the spillway removing enough debris to fill a football field three stories deep.
The three-hour tour of the gorge travels a little more than a mile and goes back 110 million years to when a shallow sea covered most of Texas. The Corps of Engineers owns the land but leases the property to GBRA as a park. Because the rocks are still very unstable, access is limited to guided tours. “We’re doing the best we can to accommodate all the people that want to take the tours,” Thomas-Jimenez says. “We just don’t have the people to lead the tours.” All the currently scheduled tours are full, but look for more opportunities to be added during the next several months. To learn more about Canyon Lake Gorge, go to www.canyongorge.org.
854th in a series. Day Trips, Vol. 2, a book of “Day Trips” 101-200, is available for $8.95, plus $3.05 for shipping, handling, and tax. Mail to: Day Trips, PO Box 33284, South Austin, TX 78704.
This article appears in November 16 • 2007.
