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 develop-
ment 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 informa-
tion 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 2006Printed on recycled paper

Floods Can Happen Almost Anywhere

In the late summer of 2005, the
remarkable flooding brought by Hur-
ricane Katrina, which caused more than
$200 billion in losses, constituted the
costliest natural disaster in U.S. history.

However, even in typical years, flood-
ing 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 tech-
nology, 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 flood-
control 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-map-
ping 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 Manage-
ment 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 dur-
ing 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 govern-
ments, to fund and maintain about 7,000
streamgaging stations. These relation-
ships ensure that scientific information is
always available.

Looking Ahead
The USGS will continue research on

the physical and statistical characteris-
tics of flooding, determining how flood
frequency changes with urbanization,
climate variability, and other factors for
locations nationwide.

The USGS will also work to mod-
ernize 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 develop-
ing new methods to gather streamflow
information.

The USGS helps the public, policy-
makers, and the emergency management
community make informed decisions on
how to prepare for and react to flood haz-
ards and reduce losses from future floods.

During flooding, USGS hydrographers pre-
pare 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 previ-
ous record. (USGS photo)

USGS biologists prepare to launch a wet-
lands research boat for search and rescue
in New Orleans during flooding from Hur-
ricane Katrina, Sunday, September 4, 2005.
(USGS photo)