Flood Impacts USGS Science Priorities

•	 Cost $6 billion in average annual

losses

•	 Cause about 140 deaths each year

•	 Damage infrastructure, causing

indirect losses due to disruption of

economic activity

•	 Threaten greater losses as increased

urbanization and coastal development lead to heightened vulnerability

•	 National Streamflow Information

Program: the Federal backbone for

acquiring real-time and historical

streamflow information

•	 StreamStats: a Web-based capability

of estimating streamflow information everywhere, including places

lacking gages

• Flood forecasting: using historical

data to enable flood modeling

•	 Study climate change, which

directly affects the intensity and

frequency of floods

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2006-3026

January 2006 Printed on recycled paper

Floods Can Happen Almost Anywhere

In the late summer of 2005, the

remarkable flooding brought by Hurricane Katrina, which caused more than

$200 billion in losses, constituted the

costliest natural disaster in U.S. history.

However, even in typical years, flooding causes billions of dollars in damage

and threatens lives and property in every

State.

Natural processes, such as hurricanes,

weather systems, and snowmelt, can

cause floods. Failure of levees and dams

and inadequate drainage in urban areas

can also result in flooding.

On average, floods kill about 140

people each year and cause $6 billion in

property damage.

Although loss of life to floods during

the past half-century has declined, mostly

because of improved warning systems,

economic losses have continued to rise

due to increased urbanization and coastal

development.

Science Helps Meet the Challenge

Reduction of flood losses must be

based on the best possible understanding

of how and where floods happen and how

they cause damage.

Presidential disaster declarations related to flooding in the United States, shown by county: 

Green areas represent one declaration; yellow areas represent two declarations; orange 

areas represent three declarations; red areas represent four or more declarations between 

June 1, 1965, and June 1, 2003. Map not to scale. Sources: FEMA, Michael Baker Jr., Inc., the 

National Atlas, and the USGS

Flood Hazards—A National Threat

USGS Science Helps Build Safer Communities

Presidential disaster declarations related to flooding in the United States and Puerto Rico

During the 1993 Midwest floods, boaters 

pass an airport in Chesterfield, Mo., Friday, 

July 9, 1993. (FEMA photo/Andrea Booher)
 Flood Facts

•	 The 1993 Midwest flooding was the costliest river-related flood in history, at

$20 billion.

•	 More than half of all fatalities during floods are auto related, usually the result

of drivers misjudging the depth of water on a road and the force of moving

water. A car can float in just a few inches of water.

•	 The principal causes of floods in the Eastern United States and the Gulf Coast

are hurricanes and storms.

•	 The principal causes of floods in the Western United States are snowmelt and

rainstorms.

•	 Flooding is the only natural hazard for which the Federal government provides

insurance: FEMA’s National Flood Insurance Program.

For more than 100 years, the U.S.

Geological Survey (USGS) has played

a critical role in reducing flood losses

by operating a nationwide streamgage

network that monitors the water level and

flow of the Nation’s rivers and streams.

Through satellite and computer technology, streamgages transmit real-time

information, which the National Weather

Service (NWS) uses to issue warnings so

local emergency managers can get people

out of harm’s way, and operators of floodcontrol dams and levees use to take action

to reduce flood impacts.

This information is also available to

the public at http://waterdata.usgs.gov/

nwis/rt/.

Streamgages provide long-term data

that scientists need to better understand

floods and to define flood-prone areas as

well.

The USGS has developed a flood-mapping method that delivers online flood

maps—including time of arrival, depth,

and extent of flooding—before a storm

hits. See http://pubs.water.usgs.gov/

fs2004-3060/ for more information.

Streamgage data also help in designing

structures resilient to flooding and are the

basis for the Federal Emergency Management Agency’s (FEMA) National Flood

Insurance Program, the only Federal

insurance program for natural hazards. 

For More Information

http://water.usgs.gov/osw/

http://www.usgs.gov/

The USGS national streamgage

network forms the scientific basis both

for long-term planning before and after

floods and for emergency response during flooding.

Collaboration Leads to Protection

The USGS works closely with the

NWS, the Army Corps of Engineers, and

other Federal agencies and partners in

every State, as well as many local governments, to fund and maintain about 7,000

streamgaging stations. These relationships ensure that scientific information is

always available.

Looking Ahead

The USGS will continue research on

the physical and statistical characteristics of flooding, determining how flood

frequency changes with urbanization,

climate variability, and other factors for

locations nationwide.

The USGS will also work to modernize the streamgaging network and

increase its coverage and robustness.

For areas without streamgages—

roughly 90 percent of river basins in the

United States—scientists are developing new methods to gather streamflow

information.

The USGS helps the public, policymakers, and the emergency management

community make informed decisions on

how to prepare for and react to flood hazards and reduce losses from future floods.

During flooding, USGS hydrographers prepare to make a streamflow measurement at 

the White River at Petersburg, In., Tuesday, 

January 11, 2005. (Evansville Courier & 

Press/Vincent Pugliese) 

At the Sorlie Bridge between Grand Forks, 

N. Dak., and East Grand Forks, Minn., 

floodwaters from the Red River of the North 

crest at 54.35 feet, Tuesday, April 22, 1997. 

This depth was more than 24 feet above flood 

stage and more than 4 feet above the previous record. (USGS photo)

USGS biologists prepare to launch a wetlands research boat for search and rescue 

in New Orleans during flooding from Hurricane Katrina, Sunday, September 4, 2005. 

(USGS photo)