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Precipitation Floods

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.

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Precipitation Floods

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  1. Precipitation Floods

  2. Flood Frequency

  3. The 1000-Year Flood

  4. Red River Flood, April 1997

  5. Fargo, 1997

  6. Grand Forks, ND, April 1997

  7. Why the Red River Floods • Peak discharge during spring thaw • Ice jams • Glacial lake plain • Flat gradient downstream

  8. Hurricane Agnes, June, 1972

  9. 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

  10. Hurricane Camille, August 1969

  11. 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

  12. 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

  13. Weather, June 9, 1972

  14. 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

  15. Rainfall June 9-10, 1972

  16. Canyon of Rapid Creek

  17. Canyon of Rapid Creek

  18. Canyon Lake Dam

  19. Imbricated Cars

  20. 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

  21. 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

  22. 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

  23. 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

  24. Banqiao Dam After Failure

  25. Flood, Green Bay, June 1990

  26. Flood, Green Bay, June 1990

  27. Flood, Green Bay, June 1990

  28. Flood, Green Bay, June 1990

  29. Flood, Green Bay, June 1990

  30. Flood, Green Bay, June 1990

  31. Flood, Green Bay, June 1990

  32. Flood, Green Bay, June 1990

  33. Flood, Green Bay, June 1990

  34. Flood, Green Bay, June 1990

  35. Building Smart in a Flood Plain

  36. Mississippi River Flood, 1993

  37. Mississippi River Flood, 1993

  38. Mississippi River Flood, 1993

  39. Mississippi River Flood 1993

  40. Mississippi River Flood, 1993

  41. Mississippi River Flood, 1993

  42. Near-Flood, St. Louis

  43. Mississippi River Flood 1927

  44. 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.

  45. 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.

  46. 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

  47. 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

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