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Texas Hill Country is known for its landscapes, where shallow rivers wind among hills and through rugged valleys. That geography also makes it places in the U.S. for flash flooding.

In the early hours of July 4, 2025, a flash flood swept through an area of Hill Country dotted with summer camps and small towns about 70 miles northwest of San Antonio. At least in Kerr County, and 10 girls from one camp were still unaccounted for, officials said in a late afternoon update on July 6. More than a dozen .

The flooding began with a that sent water sheeting off the hillsides and into creeks. The creeks poured into the Guadalupe River.

A river gauge at Hunt, Texas, near the camp, showed how quickly the river flooded: Around 3 a.m. on July 4, the Guadalupe River was rising about 1 foot every 5 minutes at the gauge, . By 4:30 a.m., it had . As the water moved downstream, it , where it rose faster.

Flood expert , a hydrologist and civil engineer at the University of Texas at San Antonio, explains what makes this part of the country, known as Flash Flood Alley, so dangerous.

What makes Hill Country so prone to flooding?

Texas as a whole , and by a wide margin. A colleague and I analyzed data from 1959 to 2019 and found 1,069 people had died in flooding in Texas over those six decades. The next highest total was in Louisiana, with 693.

Many of those flood deaths have been in Hill County. It's part of an area known as Flash Flood Alley, a crescent of land that curves from near Dallas down to San Antonio and then westward.

The hills are steep, and the water moves quickly when it floods. This is a with soils that don't soak up much water, so the water sheets off quickly and the shallow creeks can rise fast.

When those creeks converge on a river, they can create a surge of water that wipes out homes and washes away cars and, unfortunately, anyone in its path.

Hill Country has seen some devastating flash floods. In in western Kerr County quickly flooded the Guadalupe River, triggering a flash flood similar to the one in 2025. Ten teenagers died in the rushing water.

San Antonio, at the eastern edge of Hill Country, was hit with a flash flood on June 12, 2025, that whose cars were swept away by high water from a fast-flooding creek in the early morning.

Why does the region get such strong downpours?

One reason Hill Country gets powerful downpours is the .

The escarpment is a line of cliffs and steep hills created by a geologic fault. When warm air from the Gulf rushes up the escarpment, it condenses and . That water flows down the hills quickly, from many different directions, filling streams and rivers below.

As temperatures rise, the warmer , increasing the downpour and flood risk.

The same effect can contribute to flash flooding in San Antonio, where the large amount of to control runoff adds to the risk.

What can be done to improve flash flood safety?

First, it's important for people to understand and just how fast the water can rise and flow. In many arid areas, dry or shallow creeks can quickly fill up with fast-moving water and become deadly. So people should be aware of the risks and pay attention to the weather.

Improving flood forecasting, with of the physics and water velocity at different locations, can also help.

Probabilistic forecasting, for example, can provide a range of rainfall scenarios, enabling authorities to prepare for worst-case scenarios. A scientific framework linking rainfall forecasts to the local impacts, such as streamflow, flood depth and water velocity, could also help decision-makers implement timely evacuations or road closures.

Education is particularly essential for drivers. One to two feet of moving water can . People may think their trucks and SUVs can go through anything, but fast-moving water can flip a truck and carry it away.

Officials can also do more to barricade roads when the flood risk is high to prevent people from driving into harm's way. We found that in Texas over the past six decades involved vehicles. The storm on June 12 in San Antonio was an example. It was . The cars were from an adjacent creek.

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