See how the Texas floods unfolded and why Camp Mystic was in a hazardous location

 

More than 120 people have died and at least 160 others are still missing after horrific floods struck central Texas over the July Fourth weekend. Heavy rainfall, rocky terrain, and the nearby Gulf climate combined to quickly turn the Guadalupe River into a destructive torrent across Kerr County and the Texas Hill Country.

The swath of land through which the Guadalupe passes – including Camp Mystic, where at least 27 children and counselors were killed – has earned the nickname "flash flood alley," and hundreds have died there over the years.

As the search for victims goes on, the question people are asking is: How could this happen?

It began with moisture from Tropical Storm Barry that drifted over Texas in the first few days of July, said Bob Fogarty, a meteorologist at the National Weather Service Austin/San Antonio office. There, it collided with an upper-level low pressure system, which parked it in place. 

A weather balloon launched by the weather service showed near-record moisture in the upper atmosphere, said Victor Murphy, a recently retired National Weather Service meteorologist in Texas. With enormous amount of moisture providing fuel, the winds served as the match that caused the storms to explode.

Alan Gerard, a recently retired storm specialist with the National Oceanic and Atmospheric Administration, told USA TODAY several factors converged in one of the worst possible flood locations to create a “horrific” scenario that dropped up to 16 inches of rain over the larger region from July 3 to July 5.

Data from Floodbase, a flood tracking company shows how the deluge pulsed through the watershed for days, bringing death and destruction in its wake.

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Early on July 4, the Guadalupe River at Kerrville was flowing at 3 cubic feet per second. At that rate, it would fill an Olympic-size pool in eight hours. But soon after sunrise, 7:30 a.m., it was gushing at 134,000 cubic feet per second, a rate would fill the same pool in under a second.

The river height surged from less than 12 inches to more than 34 feet, the greatest recorded there since recordkeeping began in 1997.

That discharge was the second-highest ever recorded by the stream monitor, with data going back to mid-1986. But data between 6:15 a.m. and 7:30 a.m, around the time of the peak, hasn't been released − the event was so extreme that hydrologists from the U.S. Geological Survey are still reviewing it. Kerrville is on a list of sites where crews will be conducting what are called indirect measurements based on high-water marks, according to the USGS.

Terrain and timing were the biggest factors in the storms, according to Gerard and Murphy. "The whole area is very prone to slow-moving thunderstorms, especially in the summer months,” says Dan DePodwin, vice president of forecast operations at AccuWeather.

"The reason for that is the jet stream, a fast-moving river of air at about the level that planes fly, that moves northward in the summer," said DePodwin. And because of its proximity to the Gulf, the region gets "very high rainfall rates," most often during summer, adds Gerard. 

Geology is another key factor that has earned flash flood alley its nickname. The Balcones Escarpment, running roughly parallel to Interstate 35, is a line of cliffs and steep hills created by a geologic fault, says Hatim Sharif, a hydrologist and civil engineer at the University of Texas, San Antonio. 

Hill Country is a “semi-arid area with soils that don’t soak up much water, so the water sheets off quickly and the shallow creeks can rise fast,” Sharif says. Texas Public Radio reports that limestone in the area prevents rainwater from soaking into the ground. Instead, the water rushes into valleys.

All of these factors and more were present at Camp Mystic. "The terrain is complex or varied," DePodwin says. "So you get water channeling really quickly into narrow areas − in this case the river and river basin. That then obviously flows somewhere, in this case downhill and toward the camp."

Camp Mystic is a 700-acre private Christian summer camp for girls about 6 miles south of the town of Hunt in Kerr County. That's in Texas Hill Country, an 11-million-acre region of central-west Texas. Situated between the banks of the Guadalupe River and its Cypress Creek tributary, the camp had just begun its monthlong term for hundreds of girls.

The original camp sits alongside the Guadalupe River, and a second camp nearby opened near Cypress Lake in 2020. The camps are bisected by Cypress Creek. Among the 160 missing in the floods are five campers and a counselor from Camp Mystic, which counted at least 27 children and staff among the dead.

Many of the camp's structures exist within flood hazard areas defined by the Federal Emergency Management Agency, and new buildings have been built within those boundaries over the years.

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