Flash Flood Alley facts for kids
Flash Flood Alley is a special part of Central Texas known for having more flash floods than almost anywhere else in the United States. It's a place where heavy rains can quickly turn small streams into powerful, fast-moving rivers.
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Where is Flash Flood Alley?
People don't realize what [the Guadalupe River] can do and how quickly it can do it ... It's not like the Mississippi or a lot of the other rivers that just constantly come up slowly. You know this river in ten minutes can be up 20 or 30 feet.
Flash Flood Alley is shaped like a crescent moon. It stretches across Central Texas. You can find it along the Balcones Escarpment. This area goes from west of San Antonio through Austin and Waco. It reaches to the east of Dallas. Important rivers like the Guadalupe River and Colorado River flow through this region. Experts say the Guadalupe River basin is one of the most risky places for flash floods in the country.
Why Do Flash Floods Happen Here?
Flash Flood Alley gets a lot of rain. Sometimes, this rain is so heavy that it causes regular floods. These floods can fill streets and low areas. But flash floods are different. They happen when a lot of rain falls very quickly in one spot. This overwhelms rivers and streams in a very short time.
Natural Reasons for Flooding
This area is naturally prone to flash floods. This is due to a mix of its land shape, rocks, and weather.
- Land Shape (Topography): The region has steep hills made of worn limestone. Rivers here are usually wide and shallow. They wind through hills and valleys.
- Rocks and Soil (Geology): The soil is often rocky and thin clay. This means water doesn't soak into the ground easily. Instead, it runs off quickly, like water sliding off a smooth surface.
- Weather (Climate): Warm, moist air from the Gulf of Mexico often moves towards the Balcones Escarpment. As this air rises over the hills, it cools down. This causes heavy rain to fall. This rain rushes down the steep hills, quickly filling rivers and streams. Storms also come from the Pacific Ocean. Cooler air from the Great Plains also moves in. When warm, moist air meets cooler air, it often leads to very intense rainfall.
Human Impact on Flooding
How people build and live in the area also makes flooding worse.
- Paved Surfaces: Cities like San Antonio have a lot of paved roads and buildings. These surfaces don't absorb water. This means more water runs off into drainage systems. Sometimes, these systems are old and can't handle the sudden rush of water.
- Building in Flood Plains: Many towns are built near rivers and streams. These areas are called flood plains. They are naturally low-lying and can act like funnels for water. Building here can make floods more dangerous.
- Less Permeable Surfaces: Not using materials that let water soak through, like permeable paving, also adds to the problem.
- Overgrazing: In rural areas, too much grazing by animals can damage the soil. This makes it harder for the ground to absorb water.
Climate Change and Flooding
Scientists have noticed changes in rainfall patterns. A warmer atmosphere can hold more moisture. This means that when it rains, it can rain much harder. For example, the amount of rain falling in an hour has increased in cities like San Antonio and Austin over the past few decades. This makes flash floods even more likely and intense.
Important Floods in Flash Flood Alley
Texas has experienced many floods. Experts say that Texas has more flood-related incidents than any other state. Between 2011 and 2021, there were 500 flash floods in Texas.
The Great Flood of 1913
In December 1913, between 10 and 15 inches of rain fell. This caused widespread flooding. The Brazos River overflowed and even changed its path. The Colorado River also flooded. This event led to the creation of groups like the Brazos River and Valley Improvement Association. They worked to address future flooding issues.
San Antonio Flood of 1921
In September 1921, a strong hurricane moved into Texas. The San Antonio area received a huge amount of rain, about 7.38 inches in just a few days. This caused a terrible flood. After this event, San Antonio developed important flood control plans. These included building the Olmos Dam and creating the famous River Walk. These projects helped protect the city from future floods.
Tropical Storm Amelia in 1978
In July 1978, Tropical Storm Amelia moved inland. It stalled over the Medina and Guadalupe Rivers. The Guadalupe River rose very high, over 40 feet in Comfort. This caused significant flooding.
Comfort Bus Tragedy of 1987
On July 17, 1987, a sudden flash flood occurred near Comfort, Texas. A bus carrying children was swept away at a low water crossing. This was a very sad event. Slow-moving storms had dropped a lot of rain, causing immense flooding along the Guadalupe River. The story of the event and the rescue efforts was later shared in a TV show called Rescue 911 and a movie called The Flood: Who Will Save Our Children?
Central Texas Floods of 1998
In October 1998, the remains of two hurricanes, Madeline and Lester, brought heavy rains. This caused major flooding in several rivers, including the San Jacinto, San Benard, Colorado, Lavaca, Guadalupe, and San Antonio Rivers. The city of San Antonio experienced a very rare and severe flood.
Guadalupe River Flood of 2002
The Guadalupe River flooded again in July 2002. Some areas received a year's worth of rain in just a few days. This led to widespread flooding and affected many people.
Blanco River Flood of 2015
In May 2015, the Blanco River rose incredibly fast. It went from 5 feet to 40 feet in just a few hours. This caused severe damage in Wimberley. After this flood, Wimberley installed a system to send cellphone alerts. This helps warn people quickly about rising water.
San Antonio Floods of June 2025
In June 2025, flash flooding hit San Antonio. The area upstream received over 7 inches of rain in three hours. This was one of the highest daily rainfall totals ever recorded for the city. Many cars were swept off Loop 410 when Beitel Creek flooded. This event affected many people in the area.
Central Texas Floods of July 2025
On July 4, 2025, a huge amount of rain fell in just a few hours. This happened in and around the Texas Hill Country. It was caused by a weather system that brought moisture from tropical storms. This resulted in widespread flooding across the region. The National Weather Service issued a serious warning for communities along the Guadalupe River. In places like Hunt and Comfort, the river rose incredibly fast. The city of Kerrville declared a disaster after these floods. Some areas received over 5 to 11 inches of rain. Flooding continued into July 5, with more flash flood emergencies issued for areas around Lake Travis and Comal County.
See also
- July 2025 Central Texas floods
- List of flash floods
- Hailstorm Alley
- Tornado Alley
