Flooding is a long-term event and may last a week or more. Even 6 inches of fast-moving floodwater can knock you off your feet, and a depth of 2 feet will float your car! Never try to walk, swim, or drive through such swift water. If you come upon floodwaters, stop! Turn around and go another way!
Flash Floods occur within a few minutes or hours of excessive rainfall, a dam or levee failure, or a sudden release of water held by an ice jam. They usually occur within 6 hours of the rain event. Flash floods can roll boulders, tear out trees, destroy buildings or bridges, and scour out new channels. Rapidly rising water can reach heights of 30 feet or more. Furthermore, flash flood-producing rains can also trigger catastrophic mudslides. You will not always have a warning that these deadly, sudden floods are coming. Most flood deaths are due to Flash Floods.
When a Flash Flood Watch is issued, be alert to signs of flash flooding and be ready to evacuate at a moment's notice.
When a Flash Flood Warning is issued for your area, or the moment you realize that a flash flood is imminent, act quickly to save yourself. You may have only seconds! If you are advised to evacuate, do so immediately. Move to a safe area before access is cut off by floodwater. Continue monitoring NOAA Weather Radio, television, or emergency broadcast stations for information.
Urban and Small Stream Advisories let you know that a flooding event is occurring. Specifically, small streams, streets, and low-lying areas (railroad underpasses and urban storm drains)
Flash Flood or Flood Statements will contain follow-up information regarding a flash flood/flood event.
Do Not Drive During Floods
Nearly half of all flash flood fatalities are auto-related. But how can a foot or two of water cost you your life? Water weighs 62.4 lbs per cubic foot and typically flows downstream at 6 to 12 miles an hour. When a vehicle stalls in the water, the water's momentum is transferred to the car. For each foot the water rises, 500 pounds of lateral force are applied to the car. The biggest factor, however, is buoyancy. For each foot the water rises up the side of the car, the car displaces 1,500 pounds of water. In effect, the car weighs 1,500 lbs less for each foot the water rises. Two feet of water will carry away most automobiles.
Before, During & After Floods
What You Can Do Before a Flood
- Know your flood risk and elevation above flood stage. Do your local streams or rivers flood easily? If so, be prepared to move to a place of safety.
- Know your evacuation routes.
- Keep your automobile fueled; if electric power is cut off, gas stations may not be able to operate pumps for several days.
- Store drinking water in clean bathtubs and in various containers. Water service may be interrupted.
- Keep a stock of food that requires little cooking and no refrigeration; electric power may be interrupted.
- Keep first-aid supplies on hand.
- Keep an NOAA Weather radio, a battery-operated portable radio, emergency cooking equipment, and flashlights in working order.
- Install check valves in building sewer traps to prevent flood water from backing up into the drains of your home.
During the Flood
- Avoid areas subject to sudden flooding. This includes dips, low spots, and canyons.
- Avoid already flooded and high-velocity flow areas. Do not attempt to cross flowing streams. If you come upon a flowing stream where water is above your ankles, stop! Turn around and go the other way.
- If driving, be aware that the road bed may not be washed out under floodwaters and you may be trapped or stranded. The depth of the water is not always obvious. Turn around and go another way - NEVER drive through flooded roadways!
- If the vehicle stalls, leave it immediately and seek higher ground. Rapidly rising water may engulf the vehicle and its occupants and sweep them away. Remember, it is better to be wet than dead.
- Be especially cautious at night when it is harder to recognize flood dangers.
- Do not camp or park your vehicle along streams or washes.
After the Flood
- If fresh food has come in contact with floodwaters, throw it out.
- Boil drinking water before using. Wells should be pumped out and the water tested for purity before drinking. If in doubt, call your local public health authority.
- Seek necessary medical care at the nearest hospital. Food, clothing, shelter, and first aid are available from the Red Cross.
- Do not visit disaster areas. Your presence might hamper rescue and other emergency operations.
- Electrical equipment should be checked and dried before being returned to service.
- Use flashlights, not lanterns, torches, or matches, to examine buildings. Flammables may be inside.
- Report broken utility lines to the appropriate authorities.