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

• Peak discharge during spring thaw

• Ice jams

• Glacial lake plain

• Flat gradient downstream

Hurricane Agnes, June, 1972

Hurricane Agnes

• 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 9-

10, 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

http://upload.wikimedia.org/wikipedia/en/5/5a/Banqiaomap.png

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