Here's what you need to know about flash floods: 'They can occur in all 50 states'

Flash flooding has hit swaths of the USA in recent weeks, from Tropical Depression Henri knocking out power to rapid flooding in Middle Tennessee. 

Multiple fatalities were reported after record-breaking rain surged through Tennessee this month, and families reported losing everything in the floodwaters.

Experts said there are ways to prepare for storms and flash flooding, including if you have to evacuate from your home or gather in a shelter during the coronavirus pandemic.  

Here’s what you need to know about flash flooding and how to keep you and your family safe.  

What is a flash flood?  

Flash floods can begin within minutes of storms, according to the National Weather Service.  

Flash floods are usually caused by heavy rainfall, but they can also be caused by dam or levee breaks and other factors, according to Ed Clark, director of the National Oceanic and Atmospheric Administration's National Water Center.  

“After heavy rains, they can rip through riverbeds or urban streets,” Clark said, “really just destroying everything that the waters encounter.”  

The sudden floods can occur in various terrains, but urban areas are more prone. Such environments have more paved areas, preventing water from filtering into the ground.  

Are flash floods deadly?  

They can be. According to the National Weather Service, more than 70 people have died in the USA from flooding in 2021.   

Eleven people died from floods at home and four people while walking or hiking. Twenty-four died while driving.  

Jenelle Eli, Red Cross spokesperson, told USA TODAY individuals should stay off the road during flash flood warnings, and if a roadway is flooded, they should “turn around and go another way.”  

“The adage ‘Turn around, don’t drown’ is really prescient advice,” Eli said. 

Clark called flash flooding “an extremely hazardous event,” noting that 6 inches of moving water can knock a person off his feet, while 12 inches can move smaller vehicles.  

“Particularly when faced with moving water, with flash flood situations, it's imperative that folks do not drive into those waterways,” Clark said. “We don’t know how fast that water’s moving. We don’t know how deep that water is.”   

How can I prepare before a flash flood?  

Eli told USA TODAY, “There’s no time like the present to prepare yourself and your family for emergencies, including flash floods.”  

The Red Cross encourages people to assemble an emergency preparedness kit, including food, water, a flashlight and a first aid kit. Individuals should create an evacuation plan “and ensure each family member knows how to get back in touch if they are separated during an emergency.” 

Flash flooding can come with no warning, so individuals may want to assemble kits before potential storms. 

Eli noted that during the coronavirus pandemic, families should pack masks and hand sanitizer in emergency kits.  

Emergency officials encourage people to “learn and practice evacuation routes, shelter plans and flash flood responses,” in case they need to get to higher ground quickly.

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How do I know if my area is at risk for a flash flood?  

Officials told USA TODAY that families can use the Federal Emergency Management Agency’s online resources and other tools to understand their area’s risks for flooding.  

“Know your risk,” Clark said. “It’s really important to discuss where you are relative to a body of water that’s susceptible to flash flooding. If you live near a small stream, how high is your home up?”  

Individuals can take advantage of the Emergency Alert System for information on emergencies in their area.   

A flash flood warning means that flash flooding is coming – or already underway. A flood watch means that a flash flood is a possibility for a given area.  

“Flash floods know no season. They can occur in all 50 states. They can occur really throughout the entire year,” Clark said. “So it’s really important to monitor your weather, water forecasts. Be in touch with your community, with your family.”