Amid Cycles of Drought, San Antonio is Flash Flood Alley

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Floodwaters gush out of the San Antonio River Tunnel outlet at Lone Star Boulevard Saturday morning. Decades ago, these waters would have flooded the city. Photo by Robert Rivard

Robert RivardDrought-stricken San Antonio was stunned by intense rainfall and flooding that brought the city to a near-halt Saturday morning. The San Antonio Airport reported 9.87″ of rain on Saturday alone.

That’s epic, a day that will be remembered when future storms hit hard, but it’s not a record. It’s not even the second worst day, although some local media made such claims Saturday. The city has seen worse in years past.

To show how far we’ve come managing such rainfall, the San Antonio River’s Museum Reach was re-opened by Saturday evening, although the southern reaches of the river below downtown remained closed pending a post-storm cleanup and inspection.

Floodwaters pour from the outlet of the San Antonio River Tunnel Saturday morning. Decades ago, these waters would have flooded the city and left a wake of death and destruction. Photo by Robert Rivard

Floodwaters pour from the outlet of the San Antonio River Tunnel Saturday morning. Decades ago, these waters would have flooded the city and left a wake of death and destruction. Photo by Robert Rivard

On Sept. 7, 1921, San Antonio was hit with the single biggest day of rainfall in recorded Texas history at the time. The official measurement of 23.11″ of rain caused the deaths of 51 people – many caught by surprise in their automobiles – and millions of dollars in property damage. It’s said that Houston Street was under nine feet of water.

The historic damage led to significant flood control measures in the city that can still be seen today. Over the next decade, the city would see construction of the Olmos Dam in 1925-27, at a cost of $1.5 million. The Dam has been upgraded twice, once in the 1970s when the modern remote-controlled gate system was installed and Olmos Drive was relocated, at a cost of $10 million, and again in 2010.

Since 1921, a timeline of flood control measures shows a growing city constantly taking new measures in an effort to moderate nature’s most violent storms against urban growth. The city sits in the San Antonio River Basin, a complex network of river, creeks, and streams that can be transformed in a seeming instant by heavy rainfall. The San Antonio River Authority is a good resource for gaining a better understanding.

The San Antonio River Basin drains an area of land 4,180 square miles. The basin extends from Kerr and Medina counties in the Texas Hill Country southeast toward the Gulf of Mexico. Courtesy of SARA.

The San Antonio River Basin drains an area of land 4,180 square miles. The basin extends from Kerr and Medina counties in the Texas Hill Country southeast toward the Gulf of Mexico. Courtesy of SARA.

The 1921 flood also helped lay the seeds for what years later would become the Paseo del Rio, a.k.a the River Walk. Click here to read a timeline assembled by the Paseo del Rio Association. A bypass channel was dug in the mid-1920s to help absorb downstream flood waters, but the uncompleted project was put on hold during the Great Depression. By the mid-1930s, city officials began to glimpse the possibilities of commercial development along the downtown stretch of the San Antonio River at the same time they worked to better control i.

By the end of the 1930s, some of the infrastructure — bridges, stairways, walkways — were completed. Work continued through World War II. River Walk landscaping, beautification, and retail development didn’t get underway in earnest until the 1960s as the city prepared for HemisFair ’68 and the first modern hotels were constructed.

The river came out of its banks along he Eagleland Reach early Saturday morning, but quickly receded thanks to the tunnel. Photo by Robert Rivard

The river came out of its banks along he Eagleland Reach early Saturday morning, but quickly receded thanks to the tunnel. Photo by Robert Rivard

New residents and visitors often are surprised to observe constant water levels, even during a storm, along the River Walk. That’s due to a number of flood control measures, perhaps none more important than the San Antonio River Tunnel, which runs for three miles from Josephine Street to its outlet on the river at Lone Star Boulevard, and carries flood waters 150 feet underground that otherwise would flood the downtown. The tunnel was begun in 1987, the same year that saw completion of the Nueva Street Dam, Bridge and Marina. The tunnel was dedicated 10 years later in 1997.

The San Pedro Creek Tunnel runs 6,000 feet, underground, on the city’s near-Westside, beginning around I-10 West near Santa Rosa Street with its outlet north of  Guadalupe Street. San Pedro Creek itself was diverted and converted into a concrete culvert through downtown, but last week Bexar County Judge Nelson Wolff announced an ambitious, $125 million public works project to restore the creek through downtown.

Big storms are part of the city’s lore and history.

Another major storm struck the city starting on Sept. 26, 1946, with 10.76″ of rain recorded on Sept. 27, leading to four deaths. Officials at the time said it was the worst storm since 1921, which in turn, was said to be the worst storm since one in 1819. In the 1946 storm, however, the Olmos Dam and the bypass channel proved engineers right. The city endured the storm with far less property damage, but the downtown was still inundated as sewers clogged and backed up. More would need to be done.

Memories are still fresh of the historic floods that hit San Antonio in 1998 and again in 2002. Just as Saturday’s rains can be traced to a weather system that moved north  out of Mexico, a pair of hurricanes off the Pacific Coast of Mexico set the stage for the rains that fell Oct. 17-18, 1998. Many locations received 12″ in a single day and 20″ or more over the two days. The city thought it could absorb a so-called 100-year flood without significant loss of human life or severe property damage, but 31 people died in the flooding and more than 1,100 homes were destroyed.

Only four years later, on July 5, 2002, the city was struck again by what also was called a 100-year flood. Nine people died and once again hundreds of homes were destroyed. This time residents downstream from the Medina Dam were evacuated as fears rose of the dam being breached. Strengthening the dam, expanding the flood plain, condemning hundreds of residences and other flood controls would require city and county leaders to commit to a $500 million, 10-year flood control plan. You can read a good account of the floods and aftermath in this story by Express-News reporter Colin McDonald.

This weekend’s rain and flooding caused widespread power outages, required emergency  caused response personnel to undertake dozens of high water rescues, shut down Highway 281 through the Olmos Basin, caused significant property damage, and led to two confirmed fatalities and one missing as of this writing. Once again, people died trapped in their vehicles.

A concerted effort has been made by officials since 1998 to educate the public about the hazards of driving across low-water crossings during rain storms, and numerous crossings are now closed by automatic gates. Yet with each storm, fire fighters and other emergency personnel are called on to make dozens, sometimes hundreds, of water rescues, many of which can prove life-threatening to rescue crews. The City also began fining negligent vehicle operators who had to be rescued, but how strictly that ordinance is enforced and whether fines are always collected is hard to document.

For most residents, San Antonio returns to normal once the storm subsides almost as quickly as the floods occur. A cursory survey on foot of the recently improved Eagleland and Mission Reaches showed that improvements and the native plantings fared well. It was an epic storm, but San Antonio has seen worse.

Water wasters: Willow Springs Golf Course sprinklers pour water on to the flooded course Saturday. Photo by laura Molberg Whitley

Water wasters: Willow Springs Golf Course sprinklers pour water on to the flooded course Saturday. Photo by Laura Molberg Whitley

Follow Robert Rivard on Twitter @rivardreport or on Facebook.

 

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7 thoughts on “Amid Cycles of Drought, San Antonio is Flash Flood Alley

  1. Excellent article. A lot of people have moved to SA since 2002, so this is a first time experience for them, but there are way too many life-long residents that don’t know the city’s history.

  2. I collect “real photo postcards” of San Antonio’s 1913 and 1921 floods. One of them, showing an intersection at St. Mary’s and Houston Streets, verifies the claim that water was at least nine feet deep. The amount of destruction and the loss of life–particularly in the Alazan area–were astounding. Newcomers often ask me why we have Olmos dam; I suppose they’ll understand the necessity now. Thanks for a great summary of San Antonio’s terrible and tragic flood history.

  3. For those who wish to understand why San Antonio floods and why the City continues to build massive infrastructure for the abatement of floods, I suggest Char Miller’s book, On the Border. You will clearly see that we will continue to flood during heavy rain events .

    Remember, water runs down hill.

  4. We will never forget Evelyn Luna – she drowned in our front yard during the floods of 2007. Her memorial was swept away by the floods on Saturday. RIP…

  5. I suspect Rivard means the San Pedro Creek tunnel runs underground for 6000 ft., not that it “runs 6,000 feet underground”. THAT would be quite an engineering feat.

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