In Flash Flooding, Your Vehicle Can Be Biggest Danger

By Jon Erdman, Weather.com
Image courtesy of Weather.com

An average of 75 people have died in the U.S. from flash floods each year from 2004-2013, according to the National Weather Service. That's more than double the average death toll from lightning.

Almost two of every three U.S. flash flood deaths from 1995-2010, excluding fatalities from Hurricane Katrina, occurred in vehicles, according to Dr. Greg Forbes, severe weather expert for The Weather Channel.

The single worst decision you can make in a flash flood is driving your vehicle into floodwaters of unknown depth. It's easy to misjudge the depth of floodwater, particularly at night. Sometimes the bridge or road masked by floodwater may have been undermined or completely washed out. 

In some cases, the flash flood event occurs over such a localized area, say one part of one county or city, that driving conditions may go from dry roads to high water in a matter of a few miles.

(EXAMPLE: Louisville metro flooding April 2015)

According to FEMA:
- Six inches of water will reach the bottom of most passenger cars, causing loss of control and potential stalling.
- A foot of water will float many vehicles.
- Two feet of rushing water will carry away most vehicles, including SUVs and pickups.
According to the U.S. Geological Survey, water 1 foot deep typically exerts 500 pounds of lateral force on a vehicle.

Once your vehicle is floating, the floodwater becomes your steering wheel. If that water is moving, your vehicle could be swept away, tipped on its side or flipped. Rising water can enter your vehicle in a manner of minutes, even seconds. The best advice we can give is to never drive through floodwaters of unknown depth. As the National Weather Service has campaigned for years: "Turn around, don't drown!"

If you are stuck in your vehicle underwater, you need to act quickly:
- Find a pocket of trapped air, usually against the rear window or roof.
- Roll a window down slowly, take a deep breath and be ready to swim.
- If the window won't open, break the window with a rescue tool (Swiss Army knife, for example).

Don't Wade Through Flood Water, Either

If floodwater is powerful enough to float and/or trap your vehicle, trying to wade through it is also a bad idea. Just 6 inches of flowing water can knock you off your feet. If you slip and fall face first, you might drown before you come to. This is a particularly dangerous situation for babies and small children.

Flowing at just 6 mph, water exerts the same force per unit area as air blowing at EF5 tornado wind speeds, according to Dr. Greg Forbes, severe weather expert for The Weather Channel. Water moving at 25 mph has the pressure equivalent of wind blowing at 790 mph, faster than the speed of sound. Forbes says the fastest floodwater speeds are thought to be around 67 mph, which may occur in steep, elevated terrain.

Your Responsibility: Be Aware

In general, awareness of the weather can save your life in a flash flood.
Download The Weather Channel's app for your smartphone and tablet or use NOAA Weather Radio to make sure you have a method of receiving flood watches and warnings.

Next time there is a risk of flash flooding, take it seriously. Stay out of the water. Don't become a statistic.

For more information, go to weather.com.

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