Motor Vehicles & Floods

Any first responder or dispatcher can attest to it. "First the rain falls, then come the phone calls" flooding into dispatch centers from stranded motorists, stalled, trapped motorists, or missing motorists. Most drivers overestimate their vehicles' capabilities and underestimated the dynamics of floodwater.

Nearly half of all flood fatalities are due to motorists attempting to drive through flood water. Walking in or near flood water is the second leading cause of flood deaths. The facts are:
  • As little as 18 to 24 inches of floodwater can carry off a vehicle.
  • As little as 6 inches of floodwater can carry off a person.
Cars and floodwater - How the fatal combination works. - NOAA National Weather Service Graphic
How It Works
Buoyancy is the biggest factor. The same force that helps float a 97,000 ton air craft carrier will float a vehicle, including 4x4s and sport utility vehicles (SUVs). In reality, a 3,000-5,000-pound vehicle is no match for the combination of slick or damaged roads, buoyancy, and the force of moving water. Whether it's an automobile, truck, or SUV, any vehicle can become buoyant enough for the driver to lose control.
  • In effect, for every foot of water, a vehicle weighs 1,500 pounds less.
  • At the same time, the lateral force created by floodwater increases (500 pounds per foot).
  • Add slick or damaged road surfaces (which can't be seen under floodwater) and the vehicle will loose traction.
  • When the vehicle is no longer under the driver's control, it may be swept away. It may stall or roll.
  • Drivers may have only seconds to get to safety. For too many each year, that will not be enough time.
Turn Around Don't Drown
Weather-related emergencies are a fact of life. Don't underestimate the 1 that takes more lives across the country each year than all of the others: floods. Turn around. Don't drown.

For more about the "Turn Around Don't Drown" campaign, including posters, stickers, and computer icons, visit the Southern Region Headquarters National Weather Service website.