River Management Case Study - Boscastle
Geography: AQA GCSE, topic 3.3.20
What Caused The 2004 Boscastle Flash Flood?
On the 16th of August 2004, there was a flash flood in Boscastle (in Cornwall).
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, channeling all of the rain into Boscastle.
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.
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 defences
- Boscastle had no flood defences. This meant that it was vulnerable to any especially heavy rainfall.
Consequences of the Boscastle Flash Flood in 2004
There were immediate and long-term consequences of the Boscastle flash flood that happened on 16th August, 2004. These consequences included:
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 damaged and destroyed parts of Boscastle.
- 58 properties were flooded. 4 of these were destroyed.
- 150 cars were swept away.
- Roads and bridges were destroyed.
Evacuation was difficult
- Evacuation was difficult because the flooding happened so fast.
- 100 people were airlifted to safety.
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.
Illness and injury
- Nobody was seriously injured. Most of the harm was due to stress and mental health.
Responses to the Boscastle Flash Flood in 2004
There were immediate and long-term responses to the Boscastle flash flood that happened on 16th August, 2004. These responses included:
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.
Deeper and wider river channel
- A new £10 million pound scheme tried to stop this happening again.
- The River Valency was widened by 3 metres and lowered by 2 metres.
- 3 gauges were introduced to monitor water levels.
Rebuilding
- Buildings and roads had to be rebuilt.
Emergency rescues
- Evacuation was difficult because the flooding happened so fast.
- 100 people were airlifted to safety.
- Nobody died.
Temporary accommodation
- People whose accommodation got flooded were put up in temporary accommodation.
Test yourself on River Management Case Study - Boscastle
When was Boscastle, England last devastated by severe flash floods?
How much rainfall did Boscastle get in a period of two hours just before the 2004 flash flood?
How much is the flood thought to have cost Boscastle?
About how many cars were transported by the floodwater into the sea during the Boscastle Flash Flood?
How many serious injuries were there as a result of the Boscastle flash flood?