Flood and Flash Flood
|Why Talk About
Floods are among the most frequent and costly natural
disasters in terms of human hardship and economic loss.
As much as 90 percent of the damage related to all
natural disasters (excluding droughts) is caused by
floods and associated debris flows. Most communities in
the United States can experience some kind of flooding.
Over the 10-year period from 1988 to 1997, floods cost
the Nation, on average, $3.7 billion annually. The
long-term (1940 to 1999) annual average of lives lost is
110 per year, mostly as a result of flash floods.
Flooding occurs in known floodplains when prolonged
rainfall over several days, intense rainfall over a
short period of time, or an ice or debris jam causes a
river or stream to overflow and flood the surrounding
area. Melting snow can combine with rain in the winter
and early spring; severe thunderstorms can bring heavy
rain in the spring and summer; or tropical cyclones can
bring intense rainfall to the coastal and inland states
in the summer and fall.
Flash floods occur within six hours of a rain event,
or after a dam or levee failure, or following a sudden
release of water held by an ice or debris jam, and flash
floods can catch people unprepared. You will not always
have a warning that these deadly, sudden floods are
coming. So if you live in areas prone to flash floods,
plan now to protect your family and property.
As land is converted from fields or woodlands to
roads and parking lots, it loses its ability to absorb
rainfall. Urbanization increases runoff two to six times
over what would occur on natural terrain. During periods
of urban flooding, streets can become swift moving
rivers, while basements and viaducts can become death
traps as they fill with water.
Several factors contribute to flooding. Two key
elements are rainfall intensity and duration. Intensity
is the rate of rainfall, and duration is how long the
rain lasts. Topography, soil conditions, and ground
cover also play important roles. Most flash flooding is
caused by slow-moving thunderstorms, thunderstorms
repeatedly moving over the same area, or heavy rains
from hurricanes and tropical storms. Floods, on the
other hand, can be slow- or fast-rising, but generally
develop over a period of hours or days.
Learn about flooding and flash flooding in your area
by contacting the local emergency management office, National Weather Service
(NWS) office or your planning and zoning
department. If you are at risk, take steps to reduce
damage and the risk of injury or loss to your family.
Floods are among the most
frequent and costly natural disasters in terms of human
hardship and economic loss . . . most communities in the
United States can experience some kind of flooding.
Know the difference between WATCHES and
A National Weather Service WATCH is a message
indicating that conditions favor the occurrence of a
certain type of hazardous weather. For example, a
severe thunderstorm watch means that a severe
thunderstorm is expected in the next six hours or so
within an area approximately 120 to 150 miles wide and
300 to 400 miles long (36,000 to 60,000 square miles).
The NWS Storm Prediction Center issues such watches.
Local NWS forecast offices issue other watches (flash
flood, winter weather, etc.) 12 to 36 hours in advance
of a possible hazardous-weather or flooding event.
Each local forecast office usually covers a state or a
portion of a state.
An NWS WARNING indicates that a hazardous event is
occurring or is imminent in about 30 minutes to an
hour. Local NWS forecast offices issue warnings on a
Many more WATCHES are issued than WARNINGS. A WATCH
is the first sign a flood may occur, and when one is
issued, you should be aware of potential flood hazards.
Be aware of flood hazards. Floods can roll
boulders, tear out trees, destroy buildings and bridges,
and scour out new channels. Flood waters can reach
heights of 10 to 20 feet and often carry a deadly cargo
of debris. Flood-producing rains can also trigger
catastrophic debris slides.
Regardless of how a flood or flash flood occurs, the
rule for being safe is simple: head for higher ground
and stay away from flood waters. Even a shallow
depth of fast-moving flood water produces more force
than most people imagine. The most dangerous thing you
can do is to try walking, swimming, or driving through
flood waters. Two feet of water will carry away most
|Plan for a
|Develop a Family Disaster Plan. Please see the
Disaster Plan" section for general family planning
information. Develop flood-specific planning. Learn
about your area's flood risk and elevation above flood
stage. Contact the Milford Chapter,
emergency management office, local National Weather
Service office, or planning and zoning department about
your area's flood risk. Knowing the elevation of your
property in relation to nearby streams and dams will let
you know if forecasted flood levels will affect your
If you are at risk from floods:
Talk to your insurance agent. Homeowners'
policies do not cover flooding. Ask about the National
Flood Insurance Program (NFIP).
Use a NOAA Weather Radio with a tone-alert
feature, or a portable, battery-powered radio (or
television) for updated emergency information.
Develop an evacuation plan. (See "Evacuation"
in the "Family Disaster Plan" section.) Everyone in
your family should know where to go if they have to
leave. Trying to make plans at the last minute can be
upsetting and create confusion.
Discuss floods with your family. Everyone
should know what to do in case all family members are
not together. Discussing floods ahead of time helps
reduce fear and anxiety and lets everyone know how to
|What to Tell
If you come upon flood waters, stop, turn
around, and go another way. Climb to higher
ground. If it is moving swiftly, even water six
inches deep can knock you off your feet. Many people
are swept away wading through flood waters, resulting
in injury or death.
Stay away from flooded areas. Even if it
seems safe, flood waters may still be rising.
Never try to walk, swim, drive, or play in flood
water. You may not be able to see on the surface
how fast flood water is moving or see holes and
If you are in a vehicle and become surrounded by
water, if you can get out safely, do so immediately
and move to higher ground. Vehicles can be swept
away in two feet of water.
Watch out for snakes in areas that were
flooded. Flood waters flush snakes from their
Stay away from creek and stream banks in flooded
and recently flooded areas. The soaked banks often
become unstable due to heavy rainfall and can suddenly
give way, tossing you into rapidly moving water.
Never play around high water, storm drains,
ditches, ravines, or culverts. It is very easy to
be swept away by fast moving water.
Throw away all food that has come into contact
with flood waters. Contaminated flood water
contains bacteria and germs. Eating foods exposed to
flood waters can make you very sick.
|How to Protect
Keep insurance policies, documents, and other
valuables in a safe-deposit box. You may need
quick, easy access to these documents. Keep them in a
safe place less likely to be damaged during a
Avoid building in a floodplain unless you
elevate and reinforce your home. Some communities
do not permit building in known floodplains. If there
are no restrictions, and you are building in a
floodplain, take precautions, making it less likely
your home will be damaged during a flood.
Raise your furnace, water heater, and electric
panel to higher floors or the attic if they are in
areas of your home that may be flooded. Raising
this equipment will prevent damage. An undamaged water
heater may be your best source of fresh water after a
Install check valves in building sewer traps to
prevent flood water from backing up into the drains of
your home. As a last resort, when floods threaten,
use large corks or stoppers to plug showers, tubs, or
Construct barriers such as levees, berms, and
flood walls to stop flood water from entering the
building. Permission to construct such barriers
may be required by local building codes. Check local
building codes and ordinances for safety
Seal walls in basements with waterproofing
compounds to avoid seepage through cracks.
Consult with a construction professional for
further information if these and other damage
reduction measures can be taken. Check local
building codes and ordinances for safety requirements.
Contact your local emergency management office
for more information on mitigation options to further
reduce potential flood damage. Your local
emergency management office may be able to provide
additional resources and information on ways to reduce
|What to Do Before
If it has been raining hard for several hours,
or steadily raining for several days, be alert to the
possibility of a flood. Floods happen as the
ground becomes saturated.
Use a NOAA Weather Radio or a portable,
battery-powered radio (or television) for updated
emergency information. Local stations provide the
best advice for your particular situation.
Listen for distant thunder. In some types of
terrain, runoff from a faraway thunderstorm could be
headed your way.
If you are stopping your vehicle, camp or park
away from streams and washes, particularly during
threatening conditions. Flood waters can rise
quickly and carry you or your belongings away.
When in or along stream channels, be aware of
distant events, such as dam breaks or thunderstorms
that may cause flash floods in the
|What to Do During a
|What to Do During a
|When a flood or flash flood WARNING is issued:
Listen continuously to a NOAA Weather Radio, or
a portable, battery-powered radio (or television) for
updated emergency information. Local stations
provide you with the best advice for your particular
Be alert to signs of flooding. A WARNING
means a flood is imminent or is happening in the
If you live in a flood-prone area or think you
are at risk, evacuate immediately. Move quickly to
higher ground. Save yourself, not your belongings.
The most important thing is your safety.
Follow the instructions and advice of local
authorities. Local authorities are the most
informed about affected areas. They will best be able
to tell you areas to avoid.
If advised to evacuate, do so immediately.
Move to a safe area before access is cut off by flood
water. Evacuation is much simpler and safer before
flood waters become too deep for vehicles to drive
Follow recommended evacuation routes.
Shortcuts or alternate, non-recommended routes may be
blocked or damaged by flood waters.
Leave early enough to avoid being marooned by
flooded roads. Delaying too long may allow all
escape routes to become blocked.
Stay out of areas subject to flooding. Dips,
low spots, canyons, washes, etc., can become filled
If outdoors, climb to high ground and stay
there. Move away from dangerous flood waters.
If you come upon a flowing stream where water is
above your ankles, stop, turn around, and go
another way. Never try to walk, swim, or drive
through such swift water. Most flood fatalities are
caused by people attempting to drive through water, or
people playing in high water. If it is moving swiftly,
even water six inches deep can sweep you off your
|What to Do if You
Are Driving During a Flood
Avoid already flooded areas, and areas subject
to sudden flooding. Do not attempt to cross
flowing streams. Most flood fatalities are caused by
people attempting to drive through water, or people
playing in high water. The depth of water is not
always obvious. The roadbed may be washed out under
the water, and you could be stranded or trapped.
Rapidly rising water may stall the engine, engulf the
vehicle and its occupants, and sweep them away. Look
out for flooding at highway dips, bridges, and low
areas. Two feet of water will carry away most
If you are driving and come upon rapidly rising
waters, turn around and find another route. Move to
higher ground away from rivers, streams, creeks, and
storm drains. If your route is blocked by flood waters
or barricades, find another route. Barricades are
put up by local officials to protect people from
unsafe roads. Driving around them can be a serious
If your vehicle becomes surrounded by water or
the engine stalls, and if you can safely get out,
abandon your vehicle immediately and climb to higher
ground. Many deaths have resulted from attempts to
move stalled vehicles. When a vehicle stalls in the
water, the water's momentum is transferred to the car.
The lateral force of a foot of water moving at 10
miles per hour is about 500 pounds on the average
automobile. The greatest effect is buoyancy--for every
foot that water rises up the side of a car, it
displaces 1,500 pounds of the car's weight. So, two
feet of water moving at 10 miles per hour will float
virtually any car. Many persons have been swept away
by flood waters upon leaving their vehicles, which are
later found without much damage. Use caution when
abandoning your vehicle, and look for an opportunity
to move away quickly and safely to higher ground.
|What to Do After a
Flood or Flash Flood
Seek necessary medical care at the nearest
hospital or clinic. Contaminated flood waters lead
to a greater possibility of infection. Severe injuries
will require medical attention.
Help a neighbor who may require special
assistance--infants, elderly people, and people with
disabilities. Elderly people and people with
disabilities may require additional assistance. People
who care for them or who have large families may need
additional assistance in emergency situations.
Avoid disaster areas. Your presence might
hamper rescue and other emergency operations, and put
you at further risk from the residual effects of
floods, such as contaminated waters, crumbled roads,
landslides, mudflows, and other hazards.
Continue to listen to a NOAA Weather Radio or
local radio or television stations and return home
only when authorities indicate it is safe to do
so. Flood dangers do not end when the water begins
to recede; there may be flood-related hazards within
your community, which you could hear about from local
Stay out of any building if flood waters remain
around the building. Flood waters often undermine
foundations, causing sinking, floors can crack or
break and buildings can collapse.
Avoid entering ANY building (home, business, or
other) before local officials have said it is safe to
do so. Buildings may have hidden damage that makes
them unsafe. Gas leaks or electric or waterline damage
can create additional problems.
Report broken utility lines to the appropriate
authorities. Reporting potential hazards will get
the utilities turned off as quickly as possible,
preventing further hazard and injury. Check with your
utility company now about where broken lines should be
Avoid smoking inside buildings. Smoking in
confined areas can cause fires.
When entering buildings, use extreme
caution. Building damage may have occurred where
you least expect it. Watch carefully every step you
Wear sturdy shoes. The most common injury
following a disaster is cut feet.
Use battery-powered lanterns or flashlights
when examining buildings. Battery-powered
lighting is the safest and easiest, preventing fire
hazard for the user, occupants, and building.
Examine walls, floors, doors, staircases, and
windows to make sure that the building is not in
danger of collapsing.
Inspect foundations for cracks or other
damage. Cracks and damage to a foundation can
render a building uninhabitable.
Look for fire hazards. There may be broken
or leaking gas lines, flooded electrical circuits,
or submerged furnaces or electrical appliances.
Flammable or explosive materials may travel from
upstream. Fire is the most frequent hazard following
Check for gas leaks. If you smell gas or
hear a 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
Look for electrical system damage. If you
see sparks or broken or frayed wires, or if you
smell burning 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 first for advice.
Electrical equipment should be checked and dried
before being returned to service.
Check for sewage and waterline 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 using
water from the tap. You can obtain safe water from
undamaged water heaters or by melting ice cubes.
Watch out for animals, especially poisonous
snakes, that may have come into buildings with the
flood waters. Use a stick to poke through
debris. Flood waters flush snakes and many
animals out of their homes.
Watch for loose plaster, drywall, and ceilings
that could fall.
Take pictures of the damage, both of the
building and its contents, for insurance
After returning home:
Throw away food that has come in contact with
flood waters. Some canned foods may be
salvageable. If the cans are dented or damaged,
throw them away. Food contaminated by flood waters
can cause severe infections.
If water is of questionable purity, boil or
add bleach, and distill drinking water before
using. (See information on water treatment under
Supplies Kit" section.) Wells inundated by flood
waters should be pumped out and the water tested for
purity before drinking. If in doubt, call your local
public health authority. Ill health effects often
occur when people drink water contaminated with
bacteria and germs.
Pump out flooded basements gradually (about
one-third of the water per day) to avoid structural
damage. If the water is pumped completely in a
short period of time, pressure from water-saturated
soil on the outside could cause basement walls to
Service damaged septic tanks, cesspools, pits,
and leaching systems as soon as possible.
Damaged sewage systems are health
|Produced by the National Disaster
Education Coalition: American Red Cross, FEMA, IAEM,
IBHS, NFPA, NWS, USDA/CSREES, and USGS
Talking About Disaster: Guide for Standard Messages.
Produced by the National Disaster Education Coalition,
Washington, D.C., 1999.
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