Mississippi Flood 1993 Flashcards
Background of Mississippi (5)
- 3800km in length
- Flows through 10 states
- Receives over 100 major tributaries
- widest floodplain 200 km
- 300 dams
What year was Mississippi?
1993
Human causes of the Mississippi Flood (2)
- Got rid of flood plains by building on them
* The levées couldn’t stand the pressure of so much water
Physical causes of the Mississippi Flood (3)
- Cold(antarctica) and warm air(gulf of mexico) met 2000km further south so lots of rain in USA rather than snow in Canada
- Heavy rain in April saturated upper basin
- Thunderstorms in June and July -> rapid surface run-off and flash floods
How many killed in the Mississippi Flood?
43
How many evacuees from the Mississippi Flood?
50,000
How much land flooded from the Mississippi Flood?
26,000 km of land
How much did the damage cost from the Mississippi Flood?
£12 billion
What was the cost of the lost crop from the Mississippi Flood?
$2.46 billion as ground was too wet to farm
Other social effects of the Mississippi Flood (3)
- Waterways + sewage = diseases (eg. cholera)
- Lots of high insurance claims
- Area of the British Isles flooded
Why control the Mississippi? (4)
- Every time it flooded, it would change its course - unpredictable
- To make shipping easier (average paddle boat lasted 18 months)
- Shipping easier -> build economy
- Better economy = develop industry, agriculture and cities
Wing Dykes (hard)
To trap sediment to narrow the river to create a faster and deeper flow
Levées (hard)
To protect riverside development
Control Dams (hard)
To hold back floodwater
Concrete Mattresses (hard)
To stabilise banks and fix the channel in place
Blow up Meanders (hard)
To speed water downstream quicker - 250km shorter by the end
Wing Dykes evaluate (1,1)
☑Makes channel deeper and narrower by trapping sediment
☒Doesn’t stop the flooding
Levées evaluate (1,2)
☑Prevents smaller floods
☒Can make floods worse by holding back the water
☒Ugly and expensive
Control Dams evaluate (2,2)
☑Controls flood water - reservoirs
☑Can create electricity - HEP
☒Dams are very expensive to build
☒Creating a reservoir can flood settlements and farmland, destroying environment
Concrete Mattresses evaluate (2,1)
☑Fixes river in place
☑Allows development on banks
☒Expensive
Straightening Meanders evaluate (3,3)
☑Water flows to mouth more quickly
☑Reduces flood risk
☑Speeds up river - better for transportation
☒Flooding may happen downstream of where straightening has happened
☒More erosion downstream due to faster flow
☒Destroys environment - 250km shorter
Afforestation (4,3)
☑Absorbs some of the flood’s energy (interception)
☑Evapotranspiration
☑Stabilises soil
☑Jobs to look after trees
☒Takes up space
☒Doesn’t stop the flooding
☒Takes a long time to plant trees
Afforestation (soft) evaluation (4,3)
☑Absorbs some of the flood’s energy (interception)
☑Evapotranspiration
☑Stabilises soil
☑Jobs to look after trees
☒Takes up space
☒Doesn’t stop the flooding
☒Takes a long time to plant trees
Diversionary Spillways (soft) evaluation (2,2)
☑No damage to property
☑Reduced pressure in river
☒Takes up space - less space for expansion, bad for a growing population
☒Risky, it may overspill
