Case studies

Case studies

1. Boscastle

   • Causes
     • The ground was already saturated due to the previous two weeks of above average rainfall.
     • The drainage basin has many steep slopes, and has areas of impermeable slate causing rapid surface run-off.
     • Boscastle is at the confluence (where tributaries meet) of three rivers - Valency, Jordan, and Paradise. A large quantity of water all arrived within a short space of time causing the rivers to overflow.
     • The flooding coincided with a high tide, making the impact worse.
     • Small, low bridges trapped river waterand caused it to spill over
   • Effects
     • Homes (50), businesses (25) and cars belonging to more than 1,000 people were swept away.
     • Income from tourism was lost. This had an impact on livelihoods and the local economy.
     • There were vast numbers of subsequent insurance claims.
     • No lives were lost, partly due to the rapid response of the emergency services.
   • Info
     • Cornish town
     • 16th August 2004
     • Over 60mm rain fell in two hours
     • £20 million insurance payout
   • Management
     • Widened channel and lowered bed by 70cm
     • Raised car park
     • New river/flood defence wall to reduce impact
     • Bridges relocated and raised
     • Vegetation cleared from river bed

2. Bangladesh

   • Causes
     • Physical
       • Most of the country consists of a huge flood plain and delta
       • 70% of the total area is less than 1 metre above sea level
       • Bangladesh experiences heavy monsoon rains, especially over the highlands
       • The main cause was the above average & long period of heavy rain which caused all 3 rivers to have their peak flow at the same time
     • Human
       • Deforestation in Nepal and the Himalayas increases run off and adds to deposition and flooding downstream
       • Urbanisation of the flood plain has increased magnitude & frequency of floods
       • Poorly maintained embankments (levees) leak & collapse in times of high discharge
   • Effects
     • Over 57% of the land area was flooded
     • Over 1300 people were killed
     • 7 million homes were destroyed
     • 25 million people were made homeless
     • There was a serious shortage of drinking water & dry food
     • Diseases spread such as bronchitus and cholera/diarrhoea
     • Destroyed villages
     • Overall the floods cost the country almost $1 billion
   • Info
     • Is one of the poorest countries in the world with a GNP of $200 per head
     • South Asia
     • Has three of the world's most powerful rivers passing through its country - The Ganges, the Meghna & the Brahmaputra
     • 1998
     • Very densely populated
   • Management
     • Long term
       • Reduce Deforestation in Nepal & Himalayas
       • Build 7 large dams in Bangladesh to store excess water $30-$40 million and 40 yrs to complete
       • Build 5000 flood shelters to accommodate all the population
       • Build 350km of embankment - 7 metres high at a cost of $6 billion to reduce flooding along the main river channels
       • Create flood water storage areas
     • Short term
       • Boats to rescue people
       • Emergency supplies for food, water, tents and medicines
       • Repair and rebuild houses, as well as services such as sewage etc