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The deadly Fourth of July Guadalupe River flooding was a reminder to all residents of "flash flood alley" in the Hill Country and I-35 corridor of the powerful force of water.
Using water flow rates on the river during the worst part of flooding, experts calculated how much water came crashing down the waterway.
Chris Combs, an associate dean of research with the University of Texas at San Antonio's Department of Mechanical Engineering, explained: "There was really as much as 11 million pounds per second of water, which is over a million gallons per second. And if you think gallons, just like a gallon milk jug ... a million of every second flowing down the river, and it really is on par with what you see going across Niagra Falls at any given time."
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Combs said it was the combination of the water's weight, speed, and buoyancy force that made the water so deadly, and so destructive.
He said just a foot of fast-moving water can create the same force seen in a football tackle, applying 500 pounds of lateral force per foot.
The debate continues as to whether deaths were preventable with advance warnings before the river rose 26 feet in 45 minutes.
"Anyone that's there is in a very bad situation, and I think this was a very unique and rare event," Combs said. "We hope we don't see anything like this for a very long time, but I do hope that we can learn lessons from this to develop emergency preparedness actions that help make sure this never happens again."
Combs said a gallon of water weighs eight pounds, and a cubic foot of water, the size of a beach ball, weighs 60 pounds. About six inches of fast moving water can knock a person off their feet, and just one foot of fast moving water can sweep away vehicles. Fast moving water several feet higher can send homes downstream — exactly what happened in Kerr County.
