Boscastle Flood

• Was in August 2004
• Location of North coast of Cornwall
• Physical Factors

  Relief: steep v-shaped valley sides, little time for infiltration, more surface runoff
• Physical Factors

  Geology: slate is inpermable rock and granite , both prevent percolation, increase surface runoff and chance of flood
• Physical Factors

  River Valency: only small 7-8km, short lag time and flashy hydrograph
• Physical Factors

  Shape of drainage basin: circular, flashy response, all arriving at approximately the same time
• Physical Factors

  Antecedent Rainfall: Some areas of Bodmin Moor got 125% more rainfall than average, increase in saturation overland flow as soils full
• Physical Factors

  High Intensity Precipitation: approx 7 hours of storm, 200mm, 1hour 100mm/hr, caused by relief rainfall
• Human Factors

  Deforestation in the past approximately Bronze Age, less transpiration and interception, increase in surface runoff
• Environmental Impacts

  Soil erosion due to surface runoff

  Sedimentation in the river channels and into harbour creates a delta

  Bank Erosion due to high velocity of the river and high discharge.

  Bed erosion due to high velocity and high discharge means leave boulders rolling down the river

  Ecosystem impacts E.g trees removed
• Socio-economic Impacts 


  Commercial buildings destroyed: cafes, hotels, shops, tourist information

  Houses damaged, people become homeless

  116 cars destroyed, 84 removed from harbour

  Large increase in cost of flood insurance

  Fall in house prices, around 50%

  Reduce in revenue in tourism industry

  ’Dark Tourism’ visiting where tragic happened
• Social Impacts

  0 deaths

  Homelessness

  Stress
• Hard Engineering strategies to manage flood hazard

  Channelisation- deeper and wider, increase channel capacity, protect against a 75 year flood

  2004 flood- 400 year flood
• Soft Engineering strategies to manage flood hazards

  Afforestation- increase interception and transpiration reduces channel runoff

  Flood Plain Zoning- leaves area close to river empty, done on small scale

  To adapt the buildings so they’re more resilient to flooding (flood board) stop water coming through doors

  Waterproof rendering on walls, prevents materials being saturated

  No return valve fitted in toilets specially down stairs and sinks

  Electric points downstairs raised above ground level, raised floor levels downstairs slightly

  Tile flooring easier to clean