8.2.4

Flooding Case Study: Boscastle

Test yourself

What Caused The 2004 Boscastle Flash Flood?

On the 16th of August 2004, there was a flash flood in Boscastle (in Cornwall).

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Removal of vegetation

  • The removal of trees and vegetation upstream of Boscastle increased surface runoff.
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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.
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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.
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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.
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Lack of flood defences

  • Boscastle had no flood defences. This meant that it was vulnerable to any especially heavy rainfall.

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1Geography Skills

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3Geography of the World

4Development

5Weather & Climate

6The World of Work

7Natural Resources

8Rivers

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11Tectonics

12Climate Change

13Global Population & Inequality

14Urbanisation

15Ecosystems

16Life in an Emerging Country

17Analysis of Africa

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20Analysis of Bangladesh

21Analysis of Russia

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