FLOODS 

) THE AWESOME POWER 

I 

NATIONAL WEATHER SERVICE 

MENT OF COMMERCE 

' National Oceanic and Atmospheric Adm%stmtion 
*&odiag ww haw here. Tm was trying 

to gel h. He driVm on the road wr the 

stream every day. We kneu It had hem raining a lot, but it had h so dty, we were mtually happy doul the rain. Tm saw sow 

water on the rwd, but tkrmght it wn'6 thai 

akp. An$ a& all, ha was in h& huck, high 

up #the pnd. But ihn his truck stad 

toe, and befm he knew it, his truck U(LS 

wushed downstwarn wilh him in it. 

Finiunaie&, his hisck got stuck on e mk or 

somethirig, and someone saw him and thww 

him a line. Tom got out okay. Bu6 we really 

leamedfiwpt this, not to drive in floods. " 

-Testimony of Marilyn and Tom 

(last name requested to be withheld) 

lM€RVlEWED BY THE AMWCAN RED CROSS 

ARER TROPICAL STORM ALLISON STRUCK 

TEXAS M JUNE 2001 

Why Should I Be Concerned About Flooding? 

This preparedness guide explains flood-related hazards and suggests lifesaving 

actions you can take. With this information you can recognize a flood potential, 

develop a plan, and be ready when threatening weather approaches. Remember ... your safety is up to YOU! 

In the long term, floods kill more people in the United States than other types of 

severe weather. In recent years, only heat surpassed flood fatalities. Floods can 

roll boulders the size of cars, tear out trees, destroy buildings and bridges, and 

pose a significant threat to human lives. 

Online Resources 

Additional flash flood/flood-related safety information can be obtained at: 

American Red Cross Federal Emergency Management Agency 

http://www.redcross.org/ http://www.fema.gov/ 

U.S. Geological Survey National Weather Service 

http://www.usgs.gov/ http://www.nws.noaa.gov/ 

Once a river reaches flood stage, the flood severity categories used by the NWS 

include minor flooding, moderate flooding, and major flooding. Each category has 

a definition based on property damage and public threat. 

Graphical depiction of NSW b 

severity Categories. 

Flood Severity Category 

The NWS characterizes flood severity to more effectively communicate the impact 

of flooding. It uses the following categories: 

Minor Flooding - minimal or Moderate Flooding -some Major Flooding - extensive 

no property damage, but inundation of structures and inundation of structures and 

possibly some public threat roads near streams. Some roads. Significant evacuation$ 

or inconvenience. evacuations of people and/or of people andlor transfer of 

transfer of property to higher property to higher elevations. 

elevations. 

The impacts of floods 

stage associated with 

cooperation with local 

vary locally. For each NWS river forecast location, flood 

each of the NWS flood severity categories are established in 

public officials. Increasing river levels above flood stage 

constitute minor, moderate, and major flooding. Impacts vary from one river 

location to another because a certain river stage (height) above flood stage in one 

location may have an entirely different impact than the same level above flood 

rrtann at another locatinn 
I BARRICADES ARE PUT UP KXI YOUR PROTECTION. 

TURN AROUND AND GO ANOTHER WAY! 

What Are Flash Floods? 

A flash flood is a rapid rise of water along a stream or low-lying urban area. Flash 

flood damage and most fatalities tend to occur in areas immediately adjacent to a 

stream or arroyo, due to a combination of heavy rain, dam break, levee failure, rapid 

snowmelt, and ice jams. Additionally, heavy rain falling on steep terrain can weaken 

soil and cause debris flow, damaging homes, roads, and property. 

Flash floods can be produced when slow moving or multiple thunderstorms occur 

over the same area. When storms move faster, flash flooding is less likely since 

the rain is distributed over a broader area. 

Flash Flood Risk in Your Car, Truck, or Sport Utility Vehicle (SUV) 

Almost half of all flash flood fatalities occur in vehicles. Contrary to popular belief, 

many people don't realize two feet of water on a bridge or highway can float most 

vehicles. If the water is moving rapidly, the car, truck, or SUV can be swept off the 

bridge and into the creek. 

Water can erode the road bed, creating unsafe driving conditions. Underpasses can 

fill rapidly with water, while the adjacent roadway remains clear. Driving into a flooded 

underpass can quickly put you in five to six feet of water. Many flash floods occur 

at night when flooded roads are difficult to see. 

When you approach a flooded road, TURN AROUND, DON'T DROWN! 

\ 

Forces on Vehicles From High Water 

The car wi" ' 2 carried when: 

Buoyancy Force 

VshkCo Weight I 

m 
I 

I IHEAWESUME 

---- 

POWER I 

Densely populated areas have a high risk for flash floods. The construction of 

buildings, highways, driveways, and parking lots increases runoff by reducing 

the amount of rain absorbed by the ground. This runoff increases the flash flood 

potential. Sometimes, streams through cities and towns are routed underground 

into storm drains. During periods of heavy rainfall, storm drains may become 

overwhelmed and flood roads and buildings. Low spots, such as underpasses, 

underground parking garages, and basements can become death traps. 

A Photo: Harris County Flood Control District, 

Houston, Texas 

Major flooding from Tropical Storm Allison 

in Houston, Texas, June 2001. 

Embankments, known as levees, are built along rivers and are used to prevent 

high water from flooding bordering land. In 1993, many levees failed along the 

Mississippi River, resulting in devastating flesh floods. 

Dam failures have played a deadly role in the history of flash flooding. The 

United States has about 76,000 dams, and about 80 percent of those are of 

earthfill construction. Be aware of any dams upstream of your location. Earthen 

dams are more easily compromised by heavy rainfall than are concrete structures. 

Water flowing over an earthen dam can cause the dam to weaken or fail, sending 

a destructive wall of water downstream. 

Flash Flood Risk to Recreation (Camping, Hiking, Boating, Fishing) 

Many people enjoy hiking, fishing, or camping along streams and rivers. Listen to 

weather forecasts and keep away from streams if thunderstormar have happened 

or have been predicted upstream from where you are. A creek only 6 inches deep 

in mountainous areas can swell to a 10-foot deep raging river in less than an hour 

if a thunderstorm inundates the area with intense rainfall. 

When thunderstorms are in the area, stay alert for rapidly changing conditions. 

You may notice the stream start to rise quickly and become muddy. You may hear 

a roaring sound upstream that may be a flood wave moving rapidly toward you. 

Head immediately for higher ground. Don't be swept away by the rising water. Them 

am dangers associated with fast-moving water, but with common sense and some 

preparation, outdoor enthusiasts can enjoy a safe day along a stream or river. 

Source: National Weather Service h 
Where You Are Determines Your 

Flash Flood/Flood Risk 

Mountains and steep hills produce rapid runoff and quick stream response. Rocks 

and clay soils do not allow much water to infiltrate the ground. Steep narrow valleys 

generate rapid flowing waters that can rise quickly to a considerable depth. Saturated 

soil also can lead rapidly to flash flooding. 

. Very intense rainfall can produce flooding even on dry soil. In the West, most canyons 

and "small streams" are not easily recognizable as a source of danger. Canyons can 

be scoured with sudden walls of water 10-15 feet high (e.g., Antelope Canyon, 

Arizona, August 1997, 11 fatalities). 

Additionally, high risk locations include low water crossings, recent burn areas in 

mountains, and urban areas from pavement and roofs which concentrate rainfall 

runoff. 

4 Photo: Steve Allen Photography, 

Waitsfield, VT 

Road damage as a result of flash flooding. 
I THE AWESOME POWER I 

I PERSISTENT THUNMR5TORMS OVER 

I THE SAME GKJGRAPHICAL AREA 

CAN LEAb TO RIVER FLOODIPJQ. 

What Are River Floods? 

A flood is the inundation of a normally dry area caused by an increased water level 

in an established watercourse. River flooding is often caused by: 

Excessive rain from tropical systems making landfall. 

Persistent thunderstorms over the same geographical area 

for extended periods of tlme. 

Comblned rainfall and snowmelt. 

Ice jam. 

?~-&*=,$FQ *~;>;..,,- '$T>: J.'.,.. 

P- z . -* ..-. ' .,. - ., . . b.. .*,.h';&.. . ..?-.,'::,. k,' :&,; 4 

Photo: Jim Rackwitz, St. Louis Post-Dispatch b 

River flooding due to excessive rain. 

Photo: Steve Allen Photography b 

River flooding due to ice jam. 
Tropical Cyclones and their Remnants 

Floods are often produced by hunicanes, tropical storms, and tropical depressions. A 

tropical cyclone's worst impact may be the inland flooding associated with torrential 

rains. 

When these storms move inland, they are typically accompanied by very heavy rain. 

If the decaying storms move slowly over land, they can produce rainfall amounts of 

20 to 40 inches over several days. Widespread flash flooding and river flooding can 

result from these slow-moving storms. 

A hurricane also can produce a deadly storm surge that inundates coastal areas as 

it makes landfall. Storm surge is water pushed on shore by the force of the winds 

swirling around the storm. This advancing surge combines with the normal tides to 

create the hurricane storm tide, which can increase the average water level 15 feet 

or more. 

The worst natural disaster in the United States, in terms of loss of life, was caused 

by a storm surge and associated coastal flooding from the great Galveston, Texas, 

hurricane of 1900. At least 8,000 people lost their lives. 

A Deaths from hurricane coastal flooding 

have fallen dramatically in recent years, 

but ston surge remains a great threat. 

"50% of deaths associated with tropical cyclones are a 

result of inland flooding over the last 30 years." 

I -Ed Rappaport, National Hurricane Center 

I I Hunicane Agnes Tropical Storm Alberto 

122 deaths 33 deaths 

Hurricane Floyd Tropical Storm Allison 

56 deaths 44 deaths I I 
, FI n-n:n.cs"' 

Stay Informed 

Listen to National Oceanic and Atmospheric Administration (NOAA) Weather 

Radio All Hazards, commercial radio, or television; or go to the lnternet for the 

latest flash flood and flood watches, warnings, and weather advisories at: 

http://iwin.nws.noaa.gov/iwin/nationalwarnings.html 

For planning purposes, Flood Hazard Map information is only a click away 

by going to the Federal Emergency Management Agency web page at: 

http://www.fema.gov/mit/tsd 

b Source: National Weather Service 

AHPS Weather Display 

The Advanced Hydrologic Prediction Service (AHPS) 

AHPS of the National Weather Service provides improved river and flood forecasting 

and water information. AHPS has a suite of graphical lnternet products to assist 

community leaders and emergency managers in making better life- and cost-savings 

decisions about evacuating people and moving property before a flood occurs. 

AHPS major themes: 

Short-term through long-term forecasts (from minutes to months 

including probabilistic products for risk management decisions). 

Real-time flood forecast maps depicting a real extent of flooding. 

More timely and accurate flash flood warnings through the use of 

enhanced flash flood decision assistance tools. 

According to the National Hydrologic Warning Council report, "Use and Benefits 

of the National Weather Service River and Flood Forecasts," AHPS, once fully 

implemented throughout the United States, will provide more than $750 million 

in economic benefits each year. 

Additional AHPS information can be obtained at: 

http://vvww.nws.noaa.gov/om/water/Ahps.shtmI 
Use NOAA Weather Radio All Hazards! 

NOAA Weather Radio All Hazards is the best way to receive warnings from the 

National Weather Service. NOAA Weather Radio All Hazards is a nationwide network 

of radio stations broadcasting continuous weather information direct from a nearby 

National Weather Service office. 

NOAA Weather Radio All Hazards broadcasts National Weather Service warnings, 

watches, forecasts, and other hazard information 24 hours a day. The average 

reception range is a 40-mile radius from the transmitter, depending on topography. 

Be aware of the potential for flooding before the heavy rainfall begins by listening 

to NOAA Weather Radio All Hazards. 

Purchase a NOAA Weather Radio All Hazards that has a battery back-up, a Specific 

Area Message Encoder (SAME) feature, which automatically alerts you when a 

Watch or Warning is issued for your county or parish, and one that can receive all 

seven NOAA Weather Radio frequencies. 

NOAA Weather Radio All Hazards can also broadcast post-event information for 

all types of hazards-both natural (earthquakes, hurricanes and volcanos) and 

environmental (chemical or oil spills). 

The NOAA Weather Radio All Hazards network has more than 650 transmitters, 

covering the 50 states, adjacent coastal waters, Puerto Rico, the U.S. Virgin 

Islands, and the U.S. Pacific Territories. NOAA Weather Radio requires a special 

radio receiver or scanner capable of receiving the signal. Broadcasts are found 

in the public service band at these seven frequencies (MHz): 162.400, 162.425, 

162.450, 162.475, 162.500, 162.525, 162.550 (also known as channels 1 through 

NOAA Weather Radio All Hazards requires a special radio receiver or scanner 

capable of picking up the signal. These receivers can be purchased at retail 

electronic and sporting good stores. 

NOAA WEATHER RADIO BAWDS: CWANNa FRMUEMClES (MH?) 
-wwm m NATIONAL WEATHER SE 

Community preparedness Plans 

After you have developed a personavfamily safety plan, find out about your community 

safety plan. Each community prone to a flash floodlflood should develop a safety 

plan. Local officials should have detailed information for your immediate area. 

Please listen and follow their recommendations before, during, and after a storm. 

TO HELP AMERICA PREPARE FOR THE RAVAGES 

OF FLASH FLOODS AND FLOODS, THE NATIONAL 

WEATHER SERVICE HAS DESIGNED STORMREADY, 

TO ARM AMERICA'S COMMUNITIES WITH THE 

COMMUNICATION AND SAFETY SKILLS NECESSARY 

TO SAVE LIVES AND PROPERTY. 

MORE INFORMATION IS AVAILABLE AT 

WWW.NWS.NOAA.GOV/STORMREADY 

The best way to prevent loss of life is to design and build communities where roads 

I remain usable and undamaged during floods, and where homes and businesses are 

protected. While this may not always be possible, it is a goal we hope every community strives to reach. 

Protect yourself, your home, your family, and your financial future. 

National Flood Insurance Program 

One of the most important things you can do to protect your home and family before 

a flood is to purchase a flood insurance policy. You can obtain one through your 

insurance company or agent. Your agent can tell you whether the standard or preferred policy (for medium or low risk) is most appropriate for you. Flood insurance 

is backed by the National Flood lnsurance Program (NFIP), administered by the 

- Federal Emergency Management Agency. Your homeowners insurance does not 

cover flood damage. Everyone has some flood risk and anyone in a participating 

community is eligible. Don't wait until a flood is coming to purchase your policy. 

It normally takes 30 days after purchase for a flood insurance policy to go into 

effect. For more information about the NFlP and flood insurance, contact your 

insurance company or call the NFlP at 800.427.4661. 

What My Community Can Do 

Provide river and rainfall readings to emergency managers and the 

National Weather Senfice. 

Establish early warning procedures. 

Create and operate a Local Flood Warning System to identify areas 

vulnerable to flooding. 

Produce and follow the flood emergemy plans. 

Contact your local emergency management agency or local National 

Weather Service office for further information on Loal Rood Warning 1 Systems, or visit: 

Check with your city or county government (start with the Building or Planning 

Office) to find out if you live in a participating community and what flood risk 

information is available where you live. 
NATIONAL WEATHER SEMCE FORECASEW 

RELY (34 A NETWORK OF ALNIOST 10,000 

f3lRWMOAQES TO MONITOR THE HEtGtiT OF 

RIVERS AND STREAMS ACROSS ME WllON 

Streamgage Data Saves Lives 

National Weather Service forecasters rely on a network of almost 10,000 streamgages 

to monitor the height of rivers and streams across the Nation. This information provides present river conditions and is the initial information needed to develop a river 

forecast. Most of the streamgages are maintained by the U.S. Geological Survey, 

the U.S. Army Corps of Engineers, and the Department of Agriculture. Some 

streamgages are read manually by dedicated volunteer observers. If you would 

like to volunteer as a cooperative observer, visit the web site at: 

http:Nwww.nws.noaa.gov/om/coop/become.htm 

Many communities nationwide have partnered with the National Weather Service 

and other federal agencies (e.g., U.S. Geological Survey and the U.S. Army Corps 

of Engineers) to implement dense networks of precipitation gages and streamgages 

to monitor and detect flooding in their community. These networks are often 

referred to as Local Flood Warning Systems. 

wzlc . ~ocal Flood Warning Sysrem 

--~!&es.collect $: rain and river data that is transmitted to NWS and Emergency Managers 

- - - - .... I.. 

o like a seesaw. Tips 

.Mimhesofrain Sfig 

)as issued a flash flood 
THE AWESOME POWER I 

What You Can Do Before the Flood.. . 

When you receive a Flood Watch: 

A Watch is issued when flooding is possible within the watch area. When a flood 

watch is issued, you should be aware of potential flood hazards. Everyone in a 

Watch area should be ready to respond and act quickly. 

Have an evacuation plan in place BEFORE flooding occurs. Flooded roads may cut 

off your escape route. Head for higher ground before the water becomes too 

deep. Remember-just six inches of rapidly flowing water can knock you off your 

feet. For information on how or what to do if you are advised to evacuate, visit the 

American Red Cross web page at: http://www.redcross.org/services/disaster/be 

~reparedlevacuat ion. html 

I in the National Flood lnsurance Program. Start with the Building or Planning 

. Department to review the Flood lnsurance Rate Maps, published by the Federal 

Emergency Management Agency. 

Develop an evacuation plan. Everyone in your family should know where to go it 

they have to leave. 

Discuss flood plans with your family. Everyone should know what to do in case 

all family members are not together. Discussing flood plans ahead of time helps 

reduce fear and anxiety and lets everyone know how to respond. 

Determine if the roads you normally travel to reach your home or job will be 

flooded during a storm. If so, look for alternative routes to use during flooding. 

Keep a NOAA Weather Radio All Hazards, a battery-powered portable radio, emergency cooking equipment, and flashlights in working order with extra batteries. 

Have a professional install check-valves in plumbing to prevent flood waters 

from backing up into the drains of your home. 

Keep your automobile fueled; if electric power is cut off, gas stations may not 

be able to operate pumps for days. 

Store drinking water in food-grade containers. Water service may be interrupted. 

Keep a stock of food requiring little cooking and no refrigeration; electric power 

may be interrupted. 

Keep first-aid supplies and prescription medicines on hand. 
once every 1 00 years, 

MMH 

Flash floods mainly occur ir 

the eastern United States, 

MYrn 

Flash floods occur onl) 

along flowing streams, 

MYTH 

Flash floods occur mainly in the 

late afternoon and evening. 

MYM 

Homeowners insurance 

policies cover flooding. 

The 100-year ftood is a cUmactic 

average; them is a 1 % ckance 

that a 1100-year flood wiW occur 

in any given year. 

rrrr 

Flash floods occw'in dl 50 states, 

including Alaska and Hawaii. 

.-. 

Flash floods can occur in dry 

myos and uTb2VI mas *e 

nomsmm. 

Many flash floods oecur at night. 

Unfortunately, many homeowners 

do not find out until it is too late that 

their policies do not cover flooding. 

Contact your insurance company 

or agent to buy flood insurance. 

You are still eligible to purchase 

flood insurance after your home, 

apartment, or business has been 

flooded, provided your community 

is participating in the National 

Flood Insurance Program. 

. .- 

Two feet of rushing water can cany 

away most vehicles including SUVs 

and pickups. 

Larger vehicles, such as SWs 

and pickups, are safe to - drive I 

through flood waters I 

DURING A FLOOD WARNING, 

DON'T DMVE 

WHENEVER POSSIBLE! 
I THE AWESOME POWER . 

What You Can Do During the Flood.. . DO NOT VISIT DISASTER AREAS 

FOLLOWING A ROD. YOUR PRESENCE 

MAY HAMPER URGENT EMERGENCY 

RESPONSE AND RESCUE OPERATIONS. 

When you recehFe a Rood Wamkrg: 

If advised to evacuate, do so immediately! Families should use only one vehicle 

/ to avoid getting separated and reduce trafRc jams. Move to a safe area before 

access is cut off by flood water. Continue listening to NOAA Weather Radio All 

Hazards, radio or television for information concerning the flooding. 

'3 Don't drive if you don't have to. 

Get out of areas subject to flooding. This includes dips, low spots, canyons, 

washes, etc. Do not attempt to cross flowing streams. 

A Photo: Federal Emergency Management 

Agw 

3 Never try to walk, swim, drive, or play in flood water. You may not be able to see 

how fast the flood water is moving or see holes or submerged debris. 

Do not camp or park your vehicle along streams and washes, particularly during 

threatening conditions. 

Be especially cautious at night when it is harder to recognize flood dangers. 

Do not attempt to drive through a flooded road. The depth of water is not always 

obvious. The road bed may be washed out wlclsr the water, and you could be 

stranded or trapped. 

Do not drive around a barricade. Barricades an, Wm & yaur paMufb~7brm 

around and go another way1 

If the vehicle stalls, leave it immediately and move to higher ground. Rapidly rising 

water may engulf the vehicle and its sweeping them away. Vehicles 

can be swept away by as little as w=. 

Children should NEVER play around Mgh water, storm drains, viaducts, or 

arroyos. It is very easy to be swepta!my by fast-moving water. 

If you come upon a fEPwin&m where water is above your ankles, STOP! Turn 

around and go anather wqd to higher ground. If it is moving swiftly, even 

water six inches desp can knock you off your feet. Many people are swept away 

wading through Rood waters, multing in injury or death. 

What You Can Do After the Flood.. . Get necessary medical care at the nearest hospital. The American Red Cross can 

help by providing shelters, food, water, and first aid, as well as helping you meet 

your immediate disaster-caused needs. 

Do not visit disaster areas. Your presence might hamper rescue and other emergency operations. 

If the power is out, use flashlights, not candles. 

Use flashlights, not lanterns, torches, or matches, to examine buildings. 

Flammables may be inside. 

Report broken utility lines to appropriate authorities. 

Boil drinking water before using. Wells should be pumped out and the water 

tested for purii before drinking. If in doubt, call your local public health authority. 

If fresh or canned food has come in contact with flood waters, throw it out. 

Take steps to reduce your risk of future floods. Make sure to follow local building 

codes and ordinances when rebuilding, and use flood-resistant materials and 

techniques to protect yourself and your propertv from future flood damaae. 
I THE AWESOME POWER 

Do You Have a Family Disaster Plan? 

Contact your local National Weather Service office, emergency Discuss the information you have gathered. Pick two places to 

management office, and American Red Cross chapter. Find out meet: a spot outside your home for an emergency such as a 

what types of disasters could occur and what you should do. Learn fire, and a place away from your neighborhood in case you can't 

about your community's methods of warning people and evacua- return home. Choose an out-of-town family member or friend as 

tion plans. Ask your insurance agent about flood insurance. Find your family check-in contact for everyone to call if the family get 

out what you can do to protect your home from the effects of separated, and a backup out-of-neighborhood friend in case the 

natural hazards that could occur where you live. Meet with your first one does not answer. Discuss what you would do and how 

II. lmplemenr your Plan 

Post emergency telephone numbers by phones and in address Teach children how and when to call 9-1 -1 or your local 

lists each person carries with them. Include cell phone numbers Emergency Medical Services number. 

of family and contact-points. Keep emergency supplies in your home sufficient for three 

Install safety features in your home, such as smoke alarms and days to a week, if your area has ever lost basic water, electrici 

fire extinguishers. and gas service for a week or longer. Assemble a disaster 

Inspect your home for wtential hazards such as items that can supplies kit with things you will need if you have to evacuate. 

move, fall, break, or catch fire, and correct them. Store these supplies in sturdy, easy-to-carry containers such 

as backpacks or duffel bags. Make physical changes that will make your home less vulnerable; 

install check-valves and hurricane shutters; strap the hot water Keep important family in a and fireheater to wall studs. resistant container. 

Have your family learn basic safety skills such as CpWAutomated Keep a smaller emergency kit with seasonal supplies, tools, 

External Defibrillator (AED) and first aid; how to use a fire extin- and clothes inthe trunk Of your car. 

. Know how to operate a it turned on to receive calls in any eme 

1 Ill. Prepare a Disaster Supplies Kit to Include: 

Battery-powered NOAA Weather Radio All Hazards 

Portable radio 

Flashlight with extra batteries 

.* Extra set of car keys 

Cash and credit card 

Special items for infant, elderly, and disabled family members 

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