Camp Mystic, where deadly Texas flooding took place, is in 'Flash Flood Alley'
A slice of central Texas called 'Flash Flood Alley' is home to many flood-prone cities, including the camp where dozens of kids perished in the July 4th flooding.
AccuWeather’s Geoff Cornish explains why central Texas, known as Flash Flood Alley, experiences some of the most sudden and severe flooding in the U.S.
Flash floods in Texas killed at least 89 people and left dozens unaccounted for on July 4 when the Guadalupe River surged early Friday following torrential rain.
The toll includes dozens of children in Kerr County, where 10 girls and one counselor are still missing from Camp Mystic, as of early Monday afternoon. Located 14 miles southwest of Kerrville, Texas, the summer camp is in an area meteorologists refer to as "Flash Flood Alley."
How much rain fell on July Fourth weekend?
Nearly a foot of rain fell in the Kerrville area between Thursday and Monday. The highest rainfall total in the state was 22.7 inches, measured 30 miles northwest of Austin near Bertram, Texas, according to the Lower Colorado River Authority.
How quickly did rivers rise near the camp?
The best data on historical flooding comes from USGS (United States Geologic Service) river flood gauges. There are three primary gauges with a robust historical record near Camp Mystic, none of which had been above flood stage during the summer camp dates in the last 17 years.
The quickest flood gauge level rise recorded during Friday's event was on the Guadalupe River at Comfort, Texas, 20 miles east of Camp Mystic. That river gauge rose 30 feet in 75 minutes, with the river spiking 12.93 feet in 15 minutes Friday morning. That's 10.34 inches per minute or an inch every 6 seconds.
When the water rises that quickly, it makes evacuations difficult, especially at night, and when a large number of people are involved, as was the case at Camp Mystic.
The river gauge on the Guadalupe at Hunt, Texas, 6 miles northwest of Camp Mystic, rose nearly 30 feet in six hours, peaking at 37.52 feet, the highest on record, beating the previous high of 36.6 feet set in 1932.
All of this took place in a region where deadly flooding is not uncommon. In fact, Texas' Flash Flood Alley is the deadliest place for flooding in the United States, according to a map created with NOAA flooding reports between 2006 and 2020.
What is Flash Flood Alley?
The Balcones Escarpment, a geological feature which roughly parallels Interstate 35, marks the edge of Flash Flood Alley. The inactive fault zone formed a rise in the topography in the area, which enhances storm systems that pass over it, causing them to dump more rain there than they might elsewhere.
"We're going from the coastal plains right into the hill country. There's a rise of at least about 500 feet in elevation," Pete Rose, a meteorologist with the Lower Colorado River Authority, told AccuWeather National Reporter Bill Wadell.
"Along with that, you have a lot of your hills and valleys that go along with that type of topography, and these hills don't contain a lot of soil; they have very thin soil. So when rain does hit them, not much of it gets absorbed," Rose said, noting that water will rush down the valleys and pile into creeks and streams.
Warm, moist air from the Gulf helps fuel storms as well, giving them ample moisture to dump lots of rain in a short amount of time across the dusty Texas soil.
Flood experts believe that the future will bring an increased risk of flash flooding to this already flood-prone area, as development in the region creates more impermeable surfaces and, as a result, more runoff. Bigger storms, enhanced by a changing climate, may also lead to more flash flooding as a warmer atmosphere allows storms to hold more water.
Officials comb through the banks of the Guadalupe River after a flash flood swept through the area Saturday, July 5, 2025, in Hunt, Texas. (AP Photo/Julio Cortez)
Cities such as Austin have been taking preventative measures to warn locals about the threat of flash flooding, putting up signs in areas that flood frequently. Austin also has a Flood Early Warning System, a network of rain gauges, barricades and cameras that monitor the threat of flooding in the city.
"We're in a very, very flash flood-prone area, not only of Texas but out of the country and even the world," Rose said.
How many people die due to flooding each year?
According to the National Weather Service (NWS), an average of 145 people in the United States die from flooding each year. Last year, there were 89 deaths. Counting the earlier flood events this year, more than 100 people have perished from flooding this year.
Additional reporting by AccuWeather's Bill Wadell.
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