According to a brochure developed jointly by the NOAA, the American Red Cross, and FEMA, almost half of all deaths from flooding happen to people trapped in vehicles. In fact, only in recent years has heat surpassed flooding as the primary cause of fatalities in the U.S. Flash floods are the most dangerous type of flooding, largely because waters rise rapidly and unexpectedly, especially in arroyos and irrigation ditches not normally associated with water, leaving most drivers (and their passengers) unprepared.
More important, water itself is a tremendous force. It weighs 62.4 pounds per cubic foot, delivering 500 pounds of pressure per square inch to doors and windows. It also makes cars buoyant, subtracting 1500 pounds from the weight of the vehicle for each foot it rises. Water a mere two feet deep can sweep away a vehicle, even a heavy-duty truck or SUV, as well as the bridge it is trapped on. Vehicles trapped in underpasses during rapidly rising water are in even more danger, and when flooding occurs at night drivers often canâ€™t see such danger until it is too late. As Carblog.com notes, even a burst water main can trigger dangerous flooding in low-lying areas.
If your area experiences several heavy rains back to back, or a sudden thaw that melts ice and release millions of gallons of water trapped in snow, you may be in danger from a flash flood. These are particularly prevalent in the U.S. West, in places like Arizona, New Mexico and California, but can occur anywhere, as witness the recent flash flooding in Arkansas which claimed 19.
NOAAâ€™s advice when you approach a flooded road is: turn around, donâ€™t drown! This bit of wisdom, offered by the Mothernaturenetwork.com (mnn.com), is clearly based on a small number of drivers who thought they could outrun a flash flood and discovered they were wrong.
If you are in a vehicle traveling over a formerly flooded area, you may want to get out and use a long stick or pole to check the roadway. Flooding frequently creates or enlarges sinkholes, which might remain hidden from view by a few inches of topsoil.
The experts at WSAV.com offer a few more flash flood tips, including never walking through more than six inches of running water (which can make you fall and pull you downstream faster than you can scream for help); never parking along streams or arroyos when weather reports indicate possible heavy rains and flooding; never driving through a barricade (they are there for a reason; often to warn of the sinkholes mentioned above); never staying with your vehicle if it stalls, but instead heading for high ground and waiting for rescue; and always keeping your radio tuned to a weather advisory channel during stormy weather.