From Drought To Flood in Two Weeks: Welcome to San Antonio

Only a month ago, San Antonio was a hot, dry semi-desert.

Scarcely any rain fell in August, with only 0.62 inches recorded at the weather station at the San Antonio International Airport. Edwards Aquifer levels were low and dropping, and some rivers had slowed to a trickle.

Then, in as little as two weeks, everything changed. Lawns that were once brown and scraggly have transformed into fields of rain lilies and mushrooms. Rivers are running high again, with some of them looking ready to spill their banks.

What kind of crazy weather is this, anyway?

Thanks to its position at the crossroads of the continent, San Antonio got a taste through the summer of the drought that caused rampant wildfires throughout the West.

But starting early this month, weather patterns shifted to allow a more tropical influence from the Gulf, University of the Incarnate Word assistant professor of meteorology Gerald Mulvey explained.

After a July in which San Antonio received above-average rainfall –  4.87 inches – a high pressure zone that established itself to the city’s west prevented moisture from the Gulf of Mexico from infiltrating this far inland, Mulvey said.

This same high-pressure zone covered a significant portion of the western U.S. At its worst point in August, San Antonio was in moderate drought.

But then, “this high pressure region, it kind of broke down a little bit, which allowed some of the kind of weak fronts that we’ve had coming through in August to reach us with some [precipitation],” Mulvey said.

With moist air moving in, Mulvey said all the ingredients for storm development are now present: moisture, wind shear, and a source of lift. The lift comes from the Balcones Escarpment – a steep limestone ridge that forms the edge of the Hill Country from Del Rio northeast past Austin.

“It was the instability in the atmosphere which wasn’t there because of that high-pressure system, which was kind of capping it,” Mulvey said.

More than 11 inches of rain have been recorded so far in September, with the most significant storms on Sept. 3.

That makes this month the third-wettest September on record, National Weather Service warning coordination meteorologist Paul Yura said. Weather records here go back to the 1880s. There’s a chance this month could set a new record.

“We have a whole rest of the month,” Yura said. “It’s plausible this could be the wettest September.”

Bexar County and its neighbors to the west, Medina and Bandera counties, are now completely free of drought conditions, according to the latest U.S. Drought Monitor map.

Rivers and Aquifer Recharged

Since Sept. 1, levels of the Edwards Aquifer have risen from 642 feet above mean sea level to 666 feet. That’s according to data from the J-17 Index Well that taps the aquifer below San Antonio.

Despite the rise, San Antonio remains under stage 2 once-a-week watering restrictions, though there’s little need for irrigation with such frequent rain.

The Edwards Aquifer Authority has not yet lifted its stage 2 pumping cutbacks of 30 percent for all wells that tap the aquifer. Officials at the Authority are waiting on confirmation from the U.S. Geological Survey that spring flows at Comal Springs in New Braunfels have recovered sufficiently to lift the cutbacks, spokesperson Ann-Margaret Gonzalez said.

Hill Country rivers have also come back to life. Stream gauges along the upper Guadalupe River, upper Medina River, and upper Frio River all show above-average flows for this time of year.

South of San Antonio, forecasters are predicting minor flooding along the Medina and San Antonio rivers in south Bexar County by Sunday afternoon.

Flooding has also brought its share of woes for the city’s urban creeks and rivers, especially sewage spills. So far this month, the San Antonio Water System has reported 26 sewage spills.

Of these, two had more than 100,000 gallons of sewage. One took place on Sept. 3 at West Commerce Street and Leon Creek. Another occurred Sept. 10 at Austin Highway near Holbrook Road.

Four spills involved more than 50,000 gallons – one on Sept. 4 at Salado Creek Greenway North, two on Sept. 7 and Sept. 10 where Pinn Road crosses Leon Creek, and one on Sept. 11 along Interstate 10 near Boerne Stage Road.

Dry Creek Beds Can Turn Deadly

Perhaps the ultimate symbol of the region’s shift between drought and flood is the low-water crossing. It’s also the reason so many people here die in flash floods.

The region of Central Texas from Dallas to San Antonio known as Flash Flood Alley has thousands of these road crossings through normally dry stream beds. They play a huge role in flood fatalities, said University of Texas at San Antonio professor Hatim Sharif.

Sharif has studied the causes of deaths from flooding in this part of the world. Texas is the No. 1 state in the U.S. for such fatalities, Sharif said.

Bexar County leads the state in the number of these deaths. According to one of Sharif’s studies, 68 people died in flood waters from 1959 to 2008.

During rains, creeks that rarely fill with water can turn into rushing torrents in a matter of minutes. But despite this danger, local governments could never afford to build bridges over every crossing, Sharif said.

“Because of the extended periods of drought, it would not be financially efficient to build bridges and sophisticated structures on small creeks,” he said. “They just assume that people shouldn’t drive through water.”

Too often, people do. As a most recent example, the San Antonio Fire Department responded to more than 60 calls for high-water rescues in a 12-hour period from Sept. 3 to Sept. 4.

That’s in spite of fines and penalties drivers can incur when they dodge barriers or call for rescue. In San Antonio, fines for circumventing barricades when there’s water on the road can reach $2,000, and the San Antonio Fire Department can charge $640 per person for emergency rescues.

“Driving through flooded roadways not only puts your life at risk and anyone in your vehicle but also the lives of our first responders,” Fire Department public relations manager Woody Woodward said in an email.

To give the public more real-time information on flooded roads, local authorities have developed BexarFlood.org, which relies on sensors transmitting data from 178 low-water crossings around San Antonio.

Sharif called the site “a good start” but said better flood warning systems would incorporate more precise data on water depth and speed. Also, more advanced flood models could help create a forecast of where street flooding is likely before a storm hits instead of after.

That may come in the future, with the San Antonio River Authority working to develop more high-quality predictive flood models. The River Authority recently passed a property tax increase meant to fund better modeling.