Case Study: Boscastle Flash Flood in 2004

• The low bridge in Boscastle 

  • A bridge over the River Valency in Boscastle was not very tall and had a low arch 
  • When the flash flood came, cars and debris became stuck under the arch creating a dam. This led to even worse flooding.  
• Removal of vegetation 

  • The removal of trees and vegetation upstream of Boscastle increased surface runoff 
• Steep relief 

  • Boscastle is in a very steep valley, which means surface runoff is high and fast  
  • The steep valley acted like a funnel, channelling all the rain into Boscastle 
• Intense rainfall  

  • 200mm of rainfall fell in 24 hours (the monthly average was 75mm) 
  • Between 50mm and 100mm fell in the space of a few hours 
  • July and August 2004 had been rainy, so there was already a lot of surface runoff 
• Lack of flood defence 

  • Boscastle has no flood defence. This mean that it was vulnerable to any especially heavy rainfall 
• Environmental pollution 

  • Environmental pollution happened as a result of about 150 cars being transported by the floodwater into the sea. 30 cars were swept out to sea 
  • 1,850 tonnes of flood debris were recovered from the surrounding area 
• Evacuation was difficult  

  • Evacuation was difficult because the flooding happened to fast  
  • 100 people were airlifted to safety 
• Decreased Tourism 

  • The flood happened during the peak season for tourism  
  • People think that the flood cost the town £50 million in damage and lost income 
• Flood damage  

  • The flood damages and destroyed parts of Boscastle  
  • 58 properties were flooded. 4 of these were destroyed 
  • 150 cars were swept away  
  • Roads and bridges were destroyed  
• Illness and injury  

  • Nobody was seriously injured. Most of the harm was due to stress and mental health 
• Deeper and wider river channel  

  • A new £10 million flood-defence scheme tried to stop this happening again 
  • The River Valency was widened by 3metres and lowered by 2 metres 
  • 3 gauges were introduced to monitor water levels  
• Emergency rescues  

  • Evacuation was difficult because the flooding happened so fast  
  • 100 people were airlifted to safety  
  • Nobody died 
• New bridge with a higher arch  

  • Increasing the height of the bridge’s arch should stop the bridge from becoming a dam if flooding happens again 
• Temporary accommodation 

  • People whose accommodation got flooded were put up in temporary accommodation  
• Rebuilding  

  • Buildings and roads had to be rebuilt