U.S. Floods of 1980
By C.A. Perry, B.N. Aldridge, and H.C. Ross of the USGS
The first significant floods of 1980 occurred February 13 to 21 in
southern California and Arizona. The floods were a result of six Pacific
storms hitting the Southwest and creating an extended period of rainfall.
This extended period of rainfall, not an excessive amount in one storm,
caused the severe flooding. The resulting volumes of runoff in many
streams south of Los Angeles, California, during February were the highest
ever recorded. The 7-day volumes on the Salt and Verde Rivers in Arizona
were the second and third highest, respectively, recorded since 1906.
These excessive volumes caused all the reservoirs in southern California,
except Lake Henshaw in San Diego County, to have spillway releases. Seven
reservoirs in Arizona on the Salt, Verde, and Agua Fria Rivers had
spillway releases. The floods caused 18 deaths and $350 million in
Intense rains hit Louisiana, Mississippi, and Alabama in two
consecutive storms in March and April. The first storm occurred from March
26 to April 2 and struck southeastern Louisiana and scattered areas in
Mississippi. The second storm lasted from April 11 to April 13 and
affected most of Mississippi and was especially intense in the area from
Baton Rouge and New Orleans, Louisiana, to Mobile, Alabama. The 2-hour
rainfall in Mobile on April 13 had a recurrence interval of 100 years. As
a result of this rainfall, Mobile experienced the worst flash floods in
the city's history.
The most devastating hydrologic event during the year occurred on May
18 with the eruption of Mount
St. Helens in Washington. The eruption caused very rapid melting of
the mountain's snow and ice, creating severe mudflows along the North Fork
Toutle, South Fork Toutle, and lower Cowlitz Rivers and throughout the
Lewis River Basin in Washington. The mudflows had substantial effects on
the streams and flood plains as large quantities of sediment were
deposited. The mudflows deposited about 11,000 acre-ft of water, mud, and
debris in Swift Reservoir on the Lewis River. The sediment that was
deposited from these mudflows caused changes in the characteristics of
flow in many of the streams in the area and required flood profiles to be
reworked in the affected areas.
The month of August brought almost continuous rain to West Virginia,
southwestern Pennsylvania, and eastern Ohio. Many precipitation stations
reported rain during almost every day from August 2 to 22, and daily
totals of 2 in. or more were very common. On August 9, thunderstorms
produced 3.0 to 3.5 in. of rain in 1 hour over Clarksburg, West Virginia .
Flooding was particularly severe in the town of Lost Creek, West Virginia.
Hurricanes and tropical storms ravaged the coastal areas of Texas in
August and September. Hurricane Allen, the first of the season, was the
most intense ever recorded in both the eastern and western parts of the
Caribbean Sea. The storm made landfall on August 9 in Texas, and tidal
surges 10 to 20 ft above sea level were recorded along the southern coast.
The tidal flooding was the worst since 1919. Tropical Storm Danielle,
which made landfall in eastern Texas on September 5, did not produce the
high winds and tidal flooding that Hurricane Allen did, but the storm did
produce torrential rains. Urban flooding caused by the excessive rainfall
was the most destructive element of this storm. Tropical Storm Jeanne in
mid-November also caused coastal flooding along the entire coast of Texas
with the worst flooding near Galveston.