The monstrous, swift-moving flood that swept through the Hill Country of Texas on Friday, killing at least 27 people and leaving many more missing, was a flash flood, the nation’s top storm-related killer. Among those missing are more than 20 girls attending a summer camp.
Authorities said about 850 people had been rescued, including some by helicopter.
Flash floods form rapidly
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.