2: Flooding Flashcards
Flood Hazards
Human Deaths Property Damage Soil Loss Loss of crops, hunger Short-term pollution of rivers Disease Fire Displacement of population
Human Deaths (worldwide/US numbers)
Worldwide: ~4000/yr (#2 natural disaster after drought)
US: 127/yr (#1 natural disaster) - 60% occurs in cars
Property Damage (worldwide/US numbers)
Worldwide: $8 billion/yr (#1 natural disaster)
US: $4 billion/yr
Flash Floods
Upstream parts of river systems or deserts
Little or no infiltration into exposed bedrock or hard soil
Localized effects…but these ares are often developed
Flash Flood Example: Big Thompson Canyon, Colorado (1976)
418 homes destroyed
$40 million in total damage
Death toll: 143
Flash Flood Example: Rapid City, South Dakota (1972)
1335 homes destroyed 5000 automobiles destroyed Damage to bridges 3000 injured 238 dead
Floodplain Floods
Occur in downstream parts of river systems
Usually result from prolonged rains
Impact wide areas
Fewer deaths and injuries than flash floods, but more damage to property
Flood Prediction
Based on the past recorded discharge of the river
The probability of a certain magnitude flood event is expressed as a…
recurrence interval
“100-year flood” chance
1% chance each year
“50-year flood” chance
2% chance each year
“500-year flood” chance
0.2% chance each year
Flood prevention
Dams Levees Floodwalls Channelization Flood retention/detention basins Regulating development on floodplains by zoning
Channelization
Straightening streams
Increases the chance of flooding downstream
Environmental problems
Restoration
Flood retention/detention basins
Storing flood waters
