Flash floods in Texas: What causes flooding on Guadalupe River that kills 32 people?

The monstrous, swift-moving flood that swept through the Hill Country of Texas on Friday, killing at least 32 people and leaving many more missing, was a flash flood, the nation's top storm-related killer. Among those missing are girls attending a summer camp on the bank of Guadalupe River. Authorities said about 850 people had been rescued, including some by helicopter. Last year, 145 people died in flash floods, according to the weather service. On average over the past 30 years, floods have claimed 127 lives annually. Nearly half of all flood-related fatalities involve vehicles. Flood deaths affect all age groups.

What is Flash Flood?

According to the National Weather Service, a flash flood is flooding that begins within six hours, and often in as little as three hours, of heavy rainfall. Waters rise so quickly that people are caught off guard, according to the weather service. Many people run into trouble while traveling. If at home or work, the water can rise so quickly people are trapped before they have time to think about escape.


That is just what happened to residents along the Guadalupe River in Kerr County and the surrounding area after at least 10 inches (25 centimeters) poured from the sky early Friday morning.

Fast-moving waters along the river rose 26 feet (8 meters) in just 45 minutes before dawn Friday, washing away homes and vehicles. The danger was not over as more heavy rains were expected Saturday and flash flood warnings and flood watches remained in effect for parts of central Texas.

On Thursday afternoon, the National Weather Service issued a flood watch, estimating rising water of up to 7 inches (17 centimeters) in spots. A “watch” means conditions are favorable for a flood and people should be prepared, but hazardous conditions might not develop.

But the watch was upgraded to a flood warning overnight, a notice that impacted 30,000 people. A warning is issued when flooding is imminent or occurring, the weather service says.

Lt,. Gov. Dan Patrick said the potential for heavy rain and flooding covered a large area and “everything was done to give them a heads-up that you could have heavy rain."

Flash Floods Prone Areas

It can happen anywhere, according to the weather service, which says that “the normally tranquil streams and creeks in your neighborhood can become raging torrents if heavy rain falls overhead.”

An area can be flooded even without rain — if it's downstream of a torrential rainstorm and a swollen stream heads its way.

Hurricanes, tropical storms, non-cyclonic weather systems carrying heavy rain and dam failures are some weather events that can cause flash flooding. They can happen in rural areas or in large cities.

FAQs

Q1. What is Flash Flood?
A1. According to the National Weather Service, a flash flood is flooding that begins within six hours, and often in as little as three hours, of heavy rainfall. Waters rise so quickly that people are caught off guard, according to the weather service. Many people run into trouble while traveling. If at home or work, the water can rise so quickly people are trapped before they have time to think about escape.

Q2. Where can flash flood take place?
A2. Flash flood can happen anywhere, according to the weather service, which says that “the normally tranquil streams and creeks in your neighborhood can become raging torrents if heavy rain falls overhead.”