On the fourth of July, the picturesque Texas Hill Country became a disaster scene along the upper Guadalupe River. After heavy rains a flash flood hit and delivered the deadliest inland flood in the U.S. in 50 years.
The numbers are staggering. Over 120 confirmed dead and over 160 people remain missing.
There were many factors that contributed to the making of this tragedy. The main contributor is The Guadalupe River and the speed of its rising. In the predawn hours of July 4th, the typically lazy river jumped 26 to 30 feet in just 45 minutes.
Just the day prior, the Guadalupe was a meager two feet. Central Texas has been in a long drought, and the river was very low, barely flowing. This made it virtually impossible for residents to imagine that hours later the river would transform into a monster. There would be a wall of water rushing downstream, blasting campgrounds, RV parks and residential communities.
What made matters worse, this was the start of a the Independence Day holiday weekend. The area was crowded with visitors, many of them not accustomed to the river’s temperamental nature. In addition, many of the visitors didn’t know that this part of Texas is called "flash flood alley."
The heavy rainfall from the atmospheric system known as a mesoscale convective vortex delivered 11 to 12 inches of rain. That vortex came from the remnants of Hurricane Barry, and it stalled over the upper Guadalupe River Water shed. It became a stubborn rain dump.
This was an uncommon weather event but not unprecedented. Longtime residents of Kerr County and The Hill Country have seen heavy rains before. Many remember the rainfall and resulting flood of July 17, 1987. It also struck the Guadalupe River Basin in South Central Texas, particularly impacting Kerr County and the city of Kerrville.
Some areas received up to 18 inches of rain in just a few hours. The intense rainfall led to flash flooding along the Guadalupe River. 10 people died, and hundreds were rescued from rooftops and trees. After that flood there were promises of better preparedness and warning systems, but a mass public alert siren system was never adopted.
But the main reason this area of about 30 counties in Texas is called flash flood alley is because of the geology there. The sloping limestone hillscape makes it almost perfectly designed for flash floods.
About 40% of flash flood events which happen in Texas happen in this region. And flash flooding is the most lethal type of flooding. Nationwide, 72% of fatalities in flood events happen in flash flood events.