Case Studies

Case Studies

1. Flooding of South Asia, 2007

   • Physical factors:
     • Monsoon came suddenly after a dry summer
     • Heavy rainfall, Assam had a record 169.5 mm in 24 hours on 22nd July.
     • Long duration of heavy rainfall saturated soil, increasing run off + river discharge..
     • Peak discharges of River Ganges + Brahmaputra coincided, increasing discharge downsteam
   • Human Factors:
     • Deforestation in Nepal in the Himalayas = less interception + increased discharge.
     • Growth of urban areas due to migration increased surface runoff
     • Collapse of old dams in India caused further flooding
   • Social Impacts
     • Over 2000 people died
       • Many reluctant to evacuate
         • Transport links were poor, evacuation was slow
       • Many children drowned, as they couldnt swim.
     • Wells polluted with sewage
       • Lack of clean drinking water
       • Over 100,000 caught water-borne diseases
     • 25 million homeless
     • 112,000 houses destroyed in India
       • Porous mud bricks became saturated by floodwater
     • Dhaka was inundated, especially poorer districts and shanty towns near rivers
     • Children lost out on education
       • 4000 schools affected
       • 44 schools destroyed
   • Economic impacts
     • Cost of flood estimated at $1 billion
     • Factories closed due to flood damage
       • Left many unemployed
     • Widespread loss of livestock, many lost their livelihoods
     • 550,000 hectares of land couldn't be planted due to flooded fields
       • World price of basmati rice rose by 10%
     • 10,000 km of roads were destroyed, landslides blocked roads
     • Debt increased for both farmers and government
   • Environmental impacts
     • Flood deposited fertile silt on flood plain
     • Rivers were polluted with sewage

2. Flooding of Carlisle, Cumbria, 2005

   • Physical Factors
     • Heavy rainfall on 6th January, 200 mm of rainfall recorded in 36 hours
     • Rain fell on saturated ground so increased run off
     • Caused a high peak discharge, over 1520 cumecs
   • Human Factors
     • Largely built up area with impermeable concrete
       • Little infiltration and high surface run off, increased discharge
     • Drains and sewage systems overflowed becoming a source of flooding.
   • Social Impacts
     • 3 people died
     • 3000+ people made homeless for upto a year
       • Seperated communities + friends
     • Children lost out on education as 4 schools flooded
     • Increase in stress related illnesses following the floods
   • Environmental impacts
     • Increased river bank erosion in areas
     • Rivers polluted with rubbish and sewage
   • Economic impacts
     • Took a year to repair, cost £100 million
     • 350 businesses shut down
       • No electricity, no telephones, no transport
     • United biscuits flooded, caused £5 million
     • 70,000 addresses had no power, police station, fire station + council offices flooded
     • 80 buses were destroyed, many roads and bridges damaged

3. Hard Engineering: 3 gorges Dam, Yangtze river

   • What did they do?
     • Built Dams + Levees on the Yangtze river
       • 3600km of levees along middle course and lower
     • Reservoir building up behind the dam, catches flood water.
       • Can store around 22km^3 of water
     • Largest HEP station in the world, 26 turbines
     • Built in locks so ships can easily travel
     • Spent $25 billion
     • 2 million people relocated
     • Destroyed habitats
   • Positive Impacts
     • Dam reduced major flooding from once every 10 years to once every 100 years
     • Turbines produce 22.5 gigawatts, enough to supply 3% of China's energy demand
     • Made it safer to navigate the Yangtze,
       • River shipping increased as bigger ships can travel up the river now
   • Negative Impacts
     • 1.3-2 million had to relocate, 13 cities and 1352 villages will be submerged
     • Reservoir will flood farmland, 650 factories , 1300 sites of cultural and historic interest
     • A huge amount of sediment carried in Yangtze river, which could lead to failure of the dam which causes catastrophic flooding
     • Dam destroyed habitats and couid endanger species
       • Endangered Siberian Crane spends the winter in wetlands below the dam, affected by less flooding
     • Doesn't protect everyone, rising water levels increase flooding along tributaries that lead into it.
       • ie: The Daning River, leads to higher erosion of river banks, causing collapses and landslides
     • Afforestation needed on slopes in the drainage basin of tributaries of the Yangtze to stop sediment piling up behind the dam

4. Development in Tundra environments, Alaska

   • Strengths

5. Soft Engineering: River Quaggy

   • Impacts
     • Creation of new habitats