|
|
| |
|
|
| |
|
|
|
|
| |
 Climate Change Indicators: River
Flooding
This indicator examines changes in the size and frequency of
inland river flood events in the United States.
Key Points
Floods have generally become larger in rivers and streams
across large parts of the Northeast and Midwest. Flood
magnitude has generally decreased in the West, southern
Appalachia, and northern Michigan (see Figure 1).
Large floods have become more frequent across the Northeast,
Pacific Northwest, and northern Great Plains. Flood
frequency has decreased in some other parts of the country,
especially the Southwest and the Rockies (see Figure 2).
Increases and decreases in frequency and magnitude of river
flood events generally coincide with increases and decreases
in the frequency of heavy rainfall events. |
|
Background
Rivers and streams experience flooding as a natural result
of large rain storms or spring snowmelt that quickly drains
into streams and rivers. Although the risk for flooding
varies across the United States, most areas are susceptible
to floods, even in dry and mountainous regions. The size, or
magnitude, of flood events is influenced by how much water
enters the waterway upstream—and how quickly. Flood
frequency largely depends on the frequency of weather
events.
Large flood events can damage homes, roads, bridges, and
other infrastructure; wipe out farmers’ crops; and harm or
displace people. Although regular flooding helps to maintain
the nutrient balance of soils in the flood plain, larger or
more frequent floods could disrupt ecosystems by displacing
aquatic life, impairing water quality, and increasing soil
erosion. By inundating water treatment systems with sediment
and contaminants, and promoting the growth of harmful
microbes, floods can directly affect the water supplies that
communities depend on.
Climate change may cause river floods to become larger or
more frequent than they used to be in some places, yet
become smaller and less frequent in other places. As warmer
temperatures cause more water to evaporate from the land and
oceans, changes in the size and frequency of heavy
precipitation events may in turn affect the size and
frequency of river flooding (see the Heavy Precipitation
indicator).1 Changes in streamflow, the timing of snowmelt
(see the Streamflow indicator), and the amount of snowpack
that accumulates in the winter (see the Snowpack indicator)
can also affect flood patterns. |
|
About the Indicator
The U.S. Geological Survey maintains thousands of stream
gauges across the United States. Each gauge measures water
level and discharge—the amount of water flowing past the
gauge. This indicator uses total daily discharge data from
about 500 long-term stream gauge stations where trends are
not substantially influenced by dams, reservoir management,
wastewater treatment facilities, or land-use change.
One way to determine whether the magnitude of flooding has
changed is by studying the largest flood event from each
year. This indicator examines the maximum discharge from
every year at every station to identify whether peak flows
have generally increased or decreased. This indicator also
analyzes whether large flood events have become more or less
frequent over time, based on daily discharge records.
This indicator starts in 1965 because flood data have been
available for a large number of sites to support a
national-level analysis since then.
Indicator Notes
This indicator is based on U.S. stream gauges that have
recorded data consistently since 1965. Besides climate
change, many other types of human influences could affect
the frequency and magnitude of floods—for example, dams,
floodwater management activities, agricultural practices,
and changes in land use. To remove these influences, this
indicator focuses on a set of sites that are not heavily
influenced by human activities, in watersheds that do not
have a large proportion of impervious surfaces such as
concrete and asphalt. Increased flooding does not
necessarily result in an increased risk to people or
property if an area has protective infrastructure, such as
levees or floodwalls.
Data Sources
Daily stream gauge data were collected by the U.S.
Geological Survey. These data came from a set of gauges in
watersheds with minimal human impacts, which have been
classified as reference gauges.6 Daily discharge data are
stored in the National Water Information System and are
publicly available at:
https://waterdata.usgs.gov/nwis.
Technical Documentation
Download related technical information PDF |
|
 Figure
1. Change in the Magnitude of River Flooding in the
United States, 1965–2015
This figure shows changes in the size of flooding events in
rivers and streams in the United States between 1965 and
2015. Blue upward-pointing symbols show locations where
floods have become larger; brown downward-pointing symbols
show locations where floods have become smaller. The larger,
solid-color symbols represent stations where the change was
statistically significant.
Data source: Slater and Villarini, 20164 |
 Figure
2. Change in the Frequency of River Flooding in the
United States, 1965–2015
This figure shows changes in the frequency of flooding
events in rivers and streams in the United States between
1965 and 2015. Blue upward-pointing symbols show locations
where floods have become more frequent; brown
downward-pointing symbols show locations where floods have
become less frequent. The larger, solid-color symbols
represent stations where the change was statistically
significant.
Data source: Slater and Villarini, 20165 |
|
|
|
EPA Page |
|
This is the
EPA page for this topic. To see if the Trump
administration has changed the EPA page, simply click the
link and compare the information with this page. If you
notice changes were made to the EPA page, please post a
comment. Thanks. |
|
|
|
|
|
|
|
|
|
|
|
|
Additional Climate Change Information |
Climate Change and Carbon Dioxide
(Beginner - Listening,
reading)
A video lesson to
help with your understanding of climate change
and carbon dioxide.
The English is
spoken at 75% of normal speed.
Great English listening and reading practice. |
Carbon Dioxide and Climate Change
(Beginner - Listening,
reading)
A video lesson to
help with your understanding of carbon dioxide
and climate change.
The English is
spoken at 75% of normal speed.
Great English listening and reading practice. |
Environmental Group Warns Earth's Health at Risk
(Beginner - Listening,
reading)
A video lesson to
help with your understanding of climate change.
The English is
spoken at 75% of normal speed.
Great English listening and reading practice.
A report by the World Wildlife Fund looked at thousands of animal populations
and found they have dropped significantly in 40 years. |
Sea Levels Rising at Fastest Rate in 3,000 years
(Beginner - Listening,
reading)
A video lesson to
help with your understanding of climate change.
The English is
spoken at 75% of normal speed.
Great English listening and reading practice.
A group of scientists say sea levels are rising at record rates. Another group
found that January temperatures in the Arctic reached a record high. |
Capturing CO2 Gas Is Not Easy
(Beginner - Listening,
reading)
A video lesson to
help with your understanding of climate change.
The English is
spoken at 75% of normal speed.
Great English listening and reading practice.
Most scientists agree that carbon-dioxide gas is partly to blame for climate
change: rising global temperatures. But capturing the CO2 gas released by power
stations is costly and difficult. |
Growth, Climate Change Threaten African Plants and
Animals
(Beginner - Listening,
reading)
A video lesson to
help with your understanding of climate change.
The English is
spoken at 75% of normal speed.
Great English listening and reading practice.
Researchers believe Africa may lose as much as 30 percent of its animal and
plant species by the end of this century. |
|
|
|
|
Search Fun Easy English |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
About
Contact
Copyright
Resources
Site Map |
