United States Search and Rescue Task Force

Flooding


FLOODS AND FLASH FLOODS

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. Flash floods can roll boulders, tear out trees, destroy buildings and 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 mud slides.  You will not always have a warning that these deadly, sudden floods are coming.  Most flood deaths are due to FLASH FLOODS.

Most flash flooding is caused by slow-moving thunderstorms, thunderstorms repeatedly moving over the same area, or heavy rains from hurricanes and tropical storms.

Types of Flooding

BEFORE

Learn flood warning signs and your community alert signals.

Request information on preparing for floods and flash floods.

If you live in a frequently flooded area, stockpile emergency building materials.


These include plywood, plastic sheeting, lumber nails, hammer and saw, pry bar,shovels, and sandbags.

Have check valves installed in building sewer traps to prevent flood watersfrom backing up in sewer drains. As a last resort, use large corks or stoppers to plug showers, tubs, or basins.

Plan and practice an evacuation route.

This plan should include information on the safest routes to shelters.  Individuals living in flash flood areas should have several alternative routes.

Have disaster supplies on hand.

Develop an emergency communication plan.   In case family members are separated from one another during floods or flashfloods (a real possibility during the day when adults are at work and children are at school), have a plan for getting back together.

Ask an out-of-state relative or friend to serve as the "family contact." After a disaster, it's often easier to call long distance.  Make sure everyone in the family knows the name, address, and phone number of the contact person.

Make sure that all family members know how to respond after a flood or flash flood.
Teach all family members how and when to turn off gas, electricity, and water.

Teach children how and when to call 9-1-1, police, fire department, and which radio station to tune to for emergency information.

Learn about the National Flood Insurance Program.  Ask your insurance agent about flood insurance.  Homeowners policies do not cover flood damage.

DURING A FLOOD WATCH

DURING A FLOOD

If Indoors:

If Outdoors:

If In A Car:

DURING AN EVACUATION

AFTER

Flood dangers do not end when the water begins to recede.  Listen to a radio or television and don't return home until authorities indicate it is safe to do so.

Remember to help your neighbors who may require special assistance--infants, elderly people, and people with disabilities.

Inspect foundations for cracks or other damage.

Stay out of buildings if flood waters remain around the building.

When entering buildings, use extreme caution.

Look for fire hazards.

Throw away food--including canned goods--that has come in contact with flood waters.

Pump out flooded basements gradually (about one-third of the water per day) to avoid structural damage.

Service damaged septic tanks, cesspools, pits, and leaching systems as soon as possible. Damaged sewage systems are health hazards.

Check for gas leaks--If you smell gas or hear blowing or hissing noise, open a window and quickly leave the building. Turn off the gas at the outside main valve if you can and call the gas company from a neighbor's home. If you turn off the gas for any reason, it must be turned back on by a professional.

Look for electrical system damage--If you see sparks or broken or frayed wires, or if you smell hot insulation, turn off the electricity at the main fuse box or circuit breaker. If you have to step in water to get to the fuse box or circuit breaker, call an electrician for advice.

Check for sewage and water lines damage--If you suspect sewage lines are damaged avoid using the toilets and call a plumber. If water pipes are damaged, contact the water company and avoid the water from the tap. You can obtain safe water by melting ice cubes.

Impacts to Automobiles

Nearly half of all flash flood fatalities are auto related!!!
Never drive your automobile into moving water, especially if you cannot tell how deep the water is.


Water weighs 62.4 lbs. per cubic foot and typically flows downstream at 6 to 12 miles per 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 is applied to the automobile.

But the biggest factor is bouyancy. For each foot the water rises up the side of the car, the car displaces 1500 lbs. of water. In effect, the automobile weighs 1500 lbs. less for each foot the water rises.

Two feet of water will carry away most automobiles!!!

FLOODING - THE HIDDEN DANGER

Nearly half of all flood related deaths occur in vehicles. Most of these deaths take place when people drive into flooded highway dips of low drainage areas. A low water crossing is where a road, without a bridge, dips across a normally dry creek bed or drainage area. Motorists who attempt to cross these flooded low water crossings are putting themselves, their vehicles and any other occupants of their vehicles at deadly risk.

Fluid Dynamics -

Water weighs about 62.4 pounds per cubic foot and typically flows downstream at 6 to 12 miles an hour. When a vehicle stalls in water, the water’s momentum is transferred to the care. For each foot the water rises, 500 pounds of lateral force are applied to the car. For each foot the water rises up the side of the car, the car displaces 1,500 pounds less for each foot the water rises. Therefore, most cars will float in just two feet of water.

The Human Element -

Most vehicles will become buoyant in two feet of water or less. People who have previously driven successfully through a flooded low water crossing often do not recognize that an increase of an inch or so in the water level may be all it takes to tip the balance of buoyancy against them. Few people including public safety and rescue personnel, appreciate the power of flowing water. Fewer people realize how fast water can rise in a small stream to flood a low water crossing area.

More than half of all low water crossing vehicular related deaths occur at night. Under conditions of low visibility the vulnerability of the driver and passengers to the hidden danger is greatly magnified. High volumes of moving water play havoc on bridges, road beds, and other structures. What may appear as a normal road, may in fact, be a death trap.

Flash Flood Warnings -

A flash flood watch means flash flooding is possible within the flash flood watch area. When a flash flood watch is posted, persons in the watch area should take precautionary measures. Keep informed and be ready for quick action if flash flooding is observed or a warning is issued. A flash flood warning means flash flooding is imminent and to take action immediately. Motorists and pedestrians in or passing through the advisory area should:

Dangerous Advertising -

With this information in mind, it can be shocking to see current television advertising for sports utility vehicles. Their advertising campaign demonstrates these vehicles driving through low water crossing areas which promotes the idea that their vehicles can handle just about anything mother nature throws at them. This can be misleading and dangerous as it presents a false sense of security.

Summary -

The general public as well as public safety and rescue personnel must remember the following critical points:

Thanks to Gerald Dworkin, NOAA and the U.S. Department of Commerce for the contents of the above article.

Water_Rescue.jpg (11960 bytes)

Water Rescue in Progress

Flooding1.jpg (7723 bytes)     Flooding2.jpg (5230 bytes)    Hurricane Picture.jpg (5496 bytes)

Severe Flooding From Hurricane Floyd in 1999