Precipitation Floods
Flood Frequency
The 1000-Year Flood
Red River Flood, April 1997
Fargo, 1997
Grand Forks, ND, April 1997
Why the Red River Floods
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Peak discharge during spring thaw
Ice jams
Glacial lake plain
Flat gradient downstream
Hurricane
Agnes,
June,
1972
Hurricane Agnes
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Weak storm but lots of rain
Richmond, Virginia flooded
Flooding along Ohio River
113 people killed from Virginia to New
York
• Chesapeake Bay severely diluted
• Agnes retired as name
• Led to formation of Conrail
Hurricane Camille, August 1969
Hurricane Camille, August 1969
• One of the most violent storms ever to hit
the U.S.
• Led to formulation of the Saffir-Simpson
intensity scale
• 143 people killed along the Gulf Coast
• 153 killed by flash flooding in Virginia and
West Virginia
• Name Camille retired
Rapid City, June 9-10, 1972
• Orographic rainfall resulting from easterly
air flow combined with unusual moisture.
• Up to 16 inches of rain in 24 hours
• >> 100 year flood
• Peak flood occurred near midnight
• Dam failed after spillway clogged with
debris
• 245 people killed
Weather, June 9, 1972
Rapid City, June 9-10, 1972
• Campers taken by surprise in Black Hills
– Dead from 13 states and France
• Numerous fatalities at nursing home
• 770 permanent homes and 550 mobile
homes destroyed
• $160 million damage
• <1% covered by flood insurance
Rainfall
June 910, 1972
Canyon of Rapid Creek
Canyon of Rapid Creek
Canyon Lake Dam
Imbricated Cars
Banqiao Dam Failures, China,
1975
• Built 1950’s for power and flood control
• Hydrologist critical of design was sacked,
reinstated, and sacked again
• Designed to survive 1000 year flood (30
cm = 12 inches rain per day)
• In 1975, >2000 year flood occurred
– 19 cm (8 inches) in one hour
– 106 cm (40 inches) in one day
Banqiao Dam Failures, China,
1975
• August 1975: Cold Front collides with
Super Typhoon Nina
• Delay in opening gates because of
communications failures and concern
about downstream flooding
• Gates blocked by sediment
• August 8, 12:30 AM: Dam upstream fails
– Designed for 500 year flood but exceeded
capacity
Banqiao Dam Failures, China,
1975
• August 8, 1 AM, Banqiao Dam overtopped
and failed
• Precipitated the failure of 62 dams
• Flood wave 10 km wide, 3-7 m high,
moving 50 km/hour
• Numerous dams opened by air strikes to
control flow
Banqiao Dam Failures, China,
1975
• One commune of 9600 people was
entirely annihilated
• 26,000 people died from flooding
• 145,000 died from subsequent epidemics
and famine.
• 9 days after the flood a million people
were still stranded
• About 6,000,000 buildings collapsed
• Details declassified in 2005
Banqiao Dam After Failure
Flood, Green Bay, June 1990
Flood, Green Bay, June 1990
Flood, Green Bay, June 1990
Flood, Green Bay, June 1990
Flood, Green Bay, June 1990
Flood, Green Bay, June 1990
Flood, Green Bay, June 1990
Flood, Green Bay, June 1990
Flood, Green Bay, June 1990
Flood, Green Bay, June 1990
Building Smart in a Flood Plain
Mississippi River Flood, 1993
Mississippi River Flood, 1993
Mississippi
River Flood,
1993
Mississippi
River Flood
1993
Mississippi River Flood, 1993
Mississippi River Flood, 1993
Near-Flood, St. Louis
Mississippi River
Flood 1927
Great Mississippi Flood, 1927
• Heavy rains in Mississippi basin during
1926
• Tributaries filled to capacity
• On April 15, 1927 15 inches of rain fell in
18 hours.
• Levee breaks in 145 places
• 27,000 square miles (70,000 km2) flooded.
Great Mississippi Flood, 1927
• Arkansas was hardest hit, with 14% of its
territory covered by floodwaters.
• By May 1927, the Mississippi River
below Memphis, Tennessee was 60 miles
wide.
• $400 million in damages
• 246 people killed in seven states.
Black and White
• 700,000 people were displaced, including
330,000 blacks who were moved to 154
relief camps.
• Whites evacuated before blacks
• Black refugees often stranded without food
or water
• Many blacks forced to work on flood
control
Black and White
• The “Great Migration,” which had been
stalled, resumed
• Black votes helped elect Herbert Hoover in
1928 on promise of reforms
• When Hoover failed to enact reforms,
blacks supported Roosevelt in 1932
• Blacks had previously voted Republican
(Lincoln’s party)
• Switched to Democratic voting
Further Effects
• Herbert Hoover was praised for his
handling of Refugee camps
• Flood led to elections of Herbert Hoover
and Huey Long
• Flood Control Act of 1928 put Army Corps
of Engineers in charge
Flood
Marker,
Cincinnati,
Ohio
Levee, Galena, Illinois
Flood Gate, Galena, Illinois
Levee, New Madrid, MO