We have used the case study of the Mississippi River flood.
The Mississippi has a high flood risk because:
- It has over 100 tributaries
- Its drainage basin covers 1/3 of the USA and some of Canada
- Heavy rain in April 1993 saturated the upper basin so storms through June and July caused a large amount of surface run-off
- An area of land the size of Britain was flooded
- Road bridges had to be closed
- 43 lives were lost and a lot of property was destroyed. There were 50,000 evacuees
- Long term effects included the fact that the water didn't go away quickly and it was still draining off the land months later
- Sewage had been washed into the water so there was a great risk of disease
- It took months to clean out houses and offices
- Stagnant water attracted mosquitoes and rats
- Human activity: dams, no water could penetrate through the soil because of buildings and concrete
Reducing the risk of flooding:
- Dams have been added to make large lakes
- Strengthen the levees
- Afforestation - trees are planted to slow down surface run-off
