Physical Geography - Case Studies

Rivers, Floods and Management
1. Causes/Impacts of flooding
  1. LEDC - Bangladesh
    1. Physical Factors
      1. Monsoon after very dry summer
      2. 170mm of rain in 24hours. 900mm in July
      3. Soil was saturated, increasing surface runoff, and discharge
      4. Peak discharge of two rivers coincided, increasing discharge downstream
    2. Human Activities
      1. Deforestation so less rainfall intercepted
      2. Growth of urban areas means more surface runoff
      3. Collapse of old damns contributed to flooding
    3. Social Impacts
      1. 2000 dead
      2. 25m homeless
      3. 100,000 caught diseases
      4. Could not evacuate due to transport issues, drowning due to lack of educaton
    4. Economic Impacts
      1. $1BN Damage
      2. Unemployment due to factories being shut
      3. Loss of livestock. 80% of citizens rely on agriculture, many lost livelihood
      4. 550,000 HA of land couldn't be planted with rice, global rice price rose
      5. 10,000km of road destroyed
      6. National debt from imports of food
    5. Environmental Impacts
      1. Rivers polluted with sewage
      2. Flood deposited fertile silt on flood plains
    6. 80% of annual rain falls in 4 months normally
    7. 90% of land is less than 10m above sea level
  2. MEDC - Carlisle, UK
    1. Physical Factors
      1. 200mm of rain in 36hours - 4 months of rain in day and a half
      2. Saturated soil, runoff straight into the river
      3. Peak discharge of 1520 cumecs, compared to average of 52cumecs
    2. Human Activities
      1. Built up with impermeable concrete/tarmac. Little vegetation for infiltration. High surface runoff and discharge
      2. Drains/sewage overflowed, becoming source of flooding itself
    3. Social Impacts
      1. 3 deaths, 3000 homeless
      2. Day to day life disrupted
      3. 4 Schools flooded
      4. Increase in stress related ilnessses
    4. Economic Impacts
      1. £100m in repairs
      2. 350 businesses had to close
      3. 70,000 buildings without power
      4. Roads/bridges damaged
    5. Environmental Impacts
      1. Increased river bank erosion
      2. Rivers polluted with rubbish
2. Flood Management Strategies
  1. Hard Engineering - Three Gorges Dam
    1. Background Info
      1. Yangtze is 3rd longest river in world
      2. Seasonal flooding common, rainy season in summer
    2. Defences
      1. 46 dams planned/built
      2. Reservoir to store flood water
      3. 3600km of levees alongside it
    3. Advantages
      1. Reduced major flooding from every decade to every century
      2. Can produce up to 22.5 gigawatts of power
      3. Much safer to navigate up river, larger ships so more shipping as deep reservoir
    4. Disadvantages
      1. Up to 2million people have to relocate
      2. Homes, factories, farmland and cultural buildings will be flooded
      3. Sediment will be blocked by dam and could cause failure, making a worse flood
      4. Could destroy habitats and endanger species
      5. Will increase flood risk in tributaries leading into it
  2. Soft Engineering - Abingdon
Coastal Environments

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