Texas ” ‘Flash Flood Alley’ geology
Explained by a hydrologist why the country of Texas Hills is known as the flash flood alley and how its geography and its geology can lead to vigorous flooding and sudden, harmful flooding
A person conducts a search near Guadalupe River in Kerrville, Texas on Sunday, July 61. Count more left lost, including 27 girls from Mystics Camp.
Desire Rios for Washington Post by Getty Images
The following essay is printed with permission from 
The conversationan online publication covering the latest research.
Texas country’s mountain country is known for its fields, where shallow streams are air in the hills and through straw valleys. That geography also makes it one of the most dead US places for Flash Flood.
In the early hours of July 4, 2025, a Flash flood passed a country area with summer camps and small towns about 70 miles northwest of San Antonio. At least 75 People died In Kerr County, and 10 girls from a camp have not yet known, officials say July 7. More than a dozen Deaths are reported in adjacent counties.
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Flooding begins with a heavy rains that sends water worn on the hills and the streams. The rivers are poured into Guadalupe River.
A river gauge in Hunt, Texas, near the camp, showing how easy it is to flood the river: at 3 am the first 5 minutes of gauge, National Weather Service Data Displays. At 4:30 am, it has risen over 20 feet. While the water is moved below, it arrived at Kerrvillewhere the river is easy.
Flood Experts Hatim SharifA hydrologist and civil engineer at the University of Texas in San Antonio, explaining what made this part of the country, known as Flash floods, is very dangerous.
What makes the hills in the country so easily flooded?
Texas as a whole leading the country’s deathand to a wide margin. A partner and I checked data from 1959 to 2019 and found 1,069 people killed in the flood of Texas for six decades. The next maximum total is in Louisiana, with 693.
Many of those who die in the flood are in Hill County. It is part of a place known to flash flooded alley, a crescent of land curves from Dallas to San Antonio and then to the west.
The hills are steep, and the water quickly transfers the flood. It is a Semi-arid area With lands that do not burden in large water, so water sheets are easy and the shallow streams can rise easily.
If the streams gather in a river, they can be a water flow that wins houses and quit cars and, unbelievable, no one in its path.
The hill mountains see some broken Flood floods. on 1987, heavy rain To quickly flooded at the Western Kerr River the Guadalupe River, who prompted a flash flood similar to one of 2025. Ten teenagers evacuated from a camp died in a hurrying water.
San Antonio, on the east side of the hill country, hit a flood flood on June 12, 2025, that killed 13 people Whose cars are striking high water from a rapid flood of the river near an interstate ramp In early morning.
Why does the region get such a strong bump?
A major country country has gained a strong depletion is Escarpment balconies.
Escarpment is a line of cliffs and steep hills made with a geologic error. If the hot air from the Gulf hurts the escarpment, it consulted and can throw a lot of moisture. That water flows the hills quickly, from many different directions, filled the rivers and the river below.
As the temperature increases, warmer Emptiness can hold more moisturewhich increases the rain and flood risk.
The same effect can contribute to the flood of San Antonio floods, which is the amount of paved soil and lack of updated channel To control the runoff adds at risk.
What can do to improve Flood safety in Flash?
First, it is important to understand people Why flash floods occur And how strong the water can rise and flow. In many arihong areas, dry or shallow streams are easily filled with water fast and fatal. So people should know the risks and pay attention to the weather.
Develop flood prediction, with More detailed models Of physics and water speeds at different locations, can also help.
For example, probabilistic predictions, can provide a variety of rainfall situations, which matches the authorities to prepare for the worst case scenarios. A city of framework connects rain forecasts to local effects, such as streamflow and water speed, can also help those who decide to decide on evacuates or road closure.
Education is more important for drivers. One to two feet of water movement can Wash a car. People may think that their trucks and SUVs can go through anything, but the movement of water can move a truck and bring it.
Officers can also make more of the barriers on the roads when the risk of flood is higher to prevent people from driving evil. We’ve seen that 58% of the flood death In Texas the past six decades involving cars. The Storm on June 12 in San Antonio is an example. it Early in the morning, and the drivers had a bad sight. The cars struck by a vigorous water flow from an adjacent stream.
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