UTSA study shows Texas needs to better prepare for future flooding

UTSA releases new study looking at the causes and consequences of the 2015 Wimberley floods. (Photo:Bettie Cross)

A new UTSA study is examining the causes and consequences of the deadly 2015 Wimberley floods.

Chad Furl, postdoctoral research associate, and Dr. Hatim Sharif, professor of civil and environmental engineering at The University of Texas at San Antonio, say urbanization is one factor that helped fuel the unprecedented flooding that sent a wall of water down the Blanco River.

“We can do better for our citizens,” said Sharif. “We can use innovation and insight to prevent more tragedies.”

On Memorial Day weekend in 2015, the Blanco River rose to a record 40 feet. The floods claimed 13 lives and damaged hundreds of homes. Furl and Sharif are studying the damage to learn what can be done to prevent a repeat.

A less rugged landscape, along with urbanization, are contributing to the problem. As natural areas become more developed, floods become more likely to occur because rain slides off concrete structures, parking lots and streets with nowhere to go.

Furl and Sharif say another factor contributing to flash floods is that Texas has heavy rain seasons in the spring and fall. That causes the soil to become oversaturated with rainwater.

“The flooding that occurred in Wimberley in 2015 were not at all uncharacteristic of the region,” Sharif said. “It had rained heavily earlier in the month, so the soil was already soaked. It couldn’t absorb any more rainwater.”

Another significant contribution to the floods was the path, intensity and timing of the storms along the Blanco River.

“The storm began upstream and moved downstream, with the water,” said Sharif. “This is very important, because in a way the river and the storm were working together by moving in the same direction. As a result, the water became faster and higher because it was being fed in the perfect way by this storm.”

The UTSA study also points out that 2015 was an unprecedented year for flooding, breaking several records. Those new records were broken again in 2016 and 2017, and the researchers say more attention needs to be paid to the warning signs.

“We saw catastrophic flooding in Houston and elsewhere just last year,” said Sharif. “The winds of Hurricane Harvey didn’t cause that devastation. It was the 275 trillion pounds of water that dented the crust of the Earth in the Houston area.”

The researchers are calling for better storm preparations to allow for the more timely blocking of roads and the evacuation of people who are in harm's way.

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