Flooding Takes
Flash flooding occurs within 6 hours of the rain event.
Flooding is a longer-term event and may last a week or more.
RIVER FLOOD
Flooding along rivers is a natural and inevitable part of life. Some floods occur seasonally when winter or spring rains, coupled with melting snows, fill river basins with too much water, too quickly. Torrential rains from decaying hurricanes or tropical systems can also produce river flooding.
COASTAL FLOOD
Winds generated from tropical storms and hurricanes or intense offshore low pressure systems can drive ocean water inland and cause significant flooding. Escape routes can be cut off and blocked by high water. Coastal flooding can also be produced by sea waves called tsunamis (tsoo-nä´-mez), sometimes referred to as tidal waves. These waves are produced by earthquakes or volcanic activity.
NOTE: Coastal flooding caused by the storm surge associated with hurricanes is described in publication NOAA/PA 78019, “Storm Surge and Hurricane Safety.”
URBAN FLOOD
As land is converted from fields or woodlands to roads and parking lots, it loses its ability to absorb rainfall.
Urbanization increases runoff 2 to 6 times over what would occur on natural terrain. During periods of urban flooding, streets can become swift moving rivers, while basements can become death traps as they fill with water.
Many Forms...
FLASH FLOODING IN ARROYOS/WASHES
An arroyo is a water-carved gully or normally dry creek bed. Arroyos can fill with fast-moving water very quickly. Flash flooding at this arroyo in Arizona took only 58 seconds to develop.
ICE JAM Floating ice can accumulate at a natural or man-made obstruction and stop the flow of water.
Environmental
Listen for...distant
thunder — runoff from a faraway thunderstorm could be headed your way.
Look out for...
Water Rising Rapidly
Nearly half of all flash flood fatalities are auto related!
In your automobile,
look out for...
flooding at highway dips, bridges, and low areas.
MANY FLASH FLOODS OCCUR AT NIGHT...
BE PREPARED TO TAKE QUICK ACTION.
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 lbs. of lateral force are applied to the car.
But the biggest factor is buoyancy. For each Two feet of water will carry away foot the water rises up the side of the car, the most automobiles. car displaces 1,500 lbs. of water. In effect, the car weighs 1,500 lbs. less for each foot the water rises.
Before the flood...
What YOU can do:
4 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.
4 Keep your automobile fueled; if electric power is cut off, gas stations may not be able to operate pumps for several days.
4 Store drinking water in clean bathtubs and in various containers. Water service may be interrupted.
4 Keep a stock of food that requires little cooking and no refrigeration; electric power may be interrupted.
4 Keep first aid supplies on hand.
4 Keep a NOAA Weather Radio, a battery-powered portable radio, emergency cooking equipment, and flashlights in working order.
4 Install check valves in building sewer traps to prevent flood water from backing up into the drains of your home.
Assemble a disaster supplies kit containing: first aid kit, canned food and can opener, bottled water, rubber boots, rubber gloves, NOAA Weather Radio, battery-powered radio, flashlight, and extra batteries.
What YOUR community can do:
4 Assist hospitals and other operations which are critically affected
by power failure by arranging for auxiliary power supplies.
4 River/rainfall readings are valuable to local emergency management agencies (EMA) and the National Weather Service (NWS) in assessing flood conditions and taking appropriate actions. Advanced warning provided by early detection is critical to saving lives. Automatic flood detection systems are available commercially for flood-prone communities. Contact your local NWS office or emergency management agency for further information on LOCAL FLOOD WARNING SYSTEMS.
STAY INFORMED ABOUT THE STORM by listening to NOAA Weather Radio, commercial radio, and television for the latest flash flood/flood
WATCHES, WARNINGS, and ADVISORIES.
NOAA WEATHER RADIO IS THE BEST MEANS TO RECEIVE WARNINGS FROM THE NATIONAL WEATHER SERVICE. The National Weather Service continuously broadcasts updated weather warnings and forecasts that can be received by NOAA Weather Radios sold in many stores. The average range is 40 miles, depending on topography. Your National Weather Service recommends purchasing a radio that has both a battery backup and a tone-alert feature which automatically alerts you when a watch or warning is issued.
What to Listen For...
FLASH FLOOD OR FLOOD WATCH: Flash flooding or flooding is possible within the designated WATCH area—be alert.
FLASH FLOOD OR FLOOD WARNING: Flash flooding or flooding has been reported or is imminent—take necessary precautions at once.
URBAN AND SMALL STREAM ADVISORY: Flooding of small streams, streets, and low-lying areas, such as railroad underpasses and urban storm drains, is occurring.
FLASH FLOOD OR FLOOD STATEMENT: Follow-up information regarding a flash flood/flood event.
The rule for being safe in a flooding situation is simple:
HEAD FOR HIGHER GROUND AND STAY AWAY FROM FLOOD WATERS!
TAKE
When a flash flood WATCH is issued — Be alert to signs of flash flooding and be ready to evacuate on 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!
Go to higher ground — Climb to safety!
