Why the Texas Mountain Country, which killed devastating floods, is one of the deadliest places for mountain floods in the United States
The Texas Hill countryside is famous for its scenery, with shallow river winds between hills and rugged valleys. The geography also makes it one of the deadliest places in the United States.
In the early morning of July 4, 2025, a mountain torrent swept through a mountainous hilly area covered with summer camps and a small town 70 miles west of San Antonio. At least 43 people died the next day, and about twelve girls in one camp are still not blamed, officials said. More than 200 people must be rescued and more rain is expected over the weekend.
The flood began with heavy downpours, moving the sliver of water out of the hillside and into the stream. The stream pours into the Guadalupe River.
National Weather Service data shows that a gauges of rivers in Hunt near the camp show the speed of water: at about 3 a.m. on July 4, the river rises about 1 foot every 5 minutes. By 4:30 a.m. it had risen more than 20 feet.
Hatim Sharif, a hydrologist and flood expert at the University of Texas San Antonio, explains what makes this part of the country, known as the Flood Lane, so dangerous.
What makes the Hill country so prone to flooding?
Texas's entire flood death toll and greater profit margins lead the country. A colleague and I analyzed data from 1959 to 2019 and found that 1,069 people died in floods in Texas during these six decades. The next highest is Louisiana, with 693.
Many of these flood deaths have been in Hill County, an area known as the Flood Lane. This is a piece of land that curves from near Dallas to the city of San Antonio and then turns west.
The hills are steep and when water floods, the water moves quickly. This is a semi-arid region where the soil does not absorb a lot of water, so the water surface drops quickly and shallow streams can rise quickly.
When these creeks converge on the river, they can generate a lot of water that makes the house wipe and wash away the cars, and unfortunately anyone is on the road.
Hill Country saw some devastating flash floods. In 1987, heavy rains in western Kerr County quickly flooded the Guadalupe River, triggering a mountain flood similar to 2025. Ten teenagers evacuated from the camp died in rapids.
Located on the eastern edge of Hill Country, San Antonio was hit by a mountain flood on June 12, 2025, killing 13 people, and their cars were swept away as they drove into high water from a flood stream near an interstate ramp early in the morning.
Why is the area pouring down?
One of the reasons Hill Country gets a strong downpour is the balcony cliff.
Cliffs are cliffs and steep hill lines created by geological faults. As the warm air from the bay rushes toward the cliff, it condenses and can dump a lot of moisture. The water flows rapidly down the hills from many different directions, filling the streams and rivers below.
As the temperature rises, a warm atmosphere can retain more moisture, increasing the risk of downpour and flooding.
The same effect could lead to mountain flooding in San Antonio, where a lot of paved land and a lack of renewed drainage to control runoff increases the risk.
How to improve the safety of mountain torrents?
First, it is important to understand why flash floods occur and how quickly water can rise and flow. In many arid areas, dry or shallow streams can quickly fill quickly with fast moving water and be fatal. Therefore, people should be aware of the risks and pay attention to the weather.
Improved flood forecasts, through more detailed models of physical and water velocities at different locations, can also help.
For example, probability prediction can provide a range of rainfall scenarios that enable authorities to prepare for the worst-case scenario. A scientific framework that links rainfall predictions to local impacts, such as water flow, flood depth and water velocity, can also help decision makers implement timely evacuation or closure of roads.
Education is especially important for drivers. One to two feet of moving water can wash away the car. People might think their trucks and SUVs can go through anything, but fast moving water can flip the truck and move it away.
When flood risk is high, officials can also have more impact on roadblocks to prevent people from falling into harm. We found that over the past six decades, 58% of flood deaths in Texas involved vehicles.
An example is the storm in San Antonio on June 12. It was early morning and the driver was less well-known. The car drove into the flood and saw no risk until it was too late.
This article was originally published on July 5, 2025 and has been updated as the death toll rises.
This article is republished from the conversation, a non-profit independent news organization that brings you factual and trustworthy analysis to help you understand our complex world. It's written: Hatim Sharif, University of Texas at San Antonio
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Hatim Sharif does not apply to, shares or funds in companies or organizations that benefit from any company or organization and does not disclose relevant affiliation except for academic appointments.
