Bostcastle - small town on north coast of Cornwall (30km NW of Plymouth)
Crackington Haven
Monday 16th August 2004
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What happened?
Flash flood as result of short periods of heavy rainfall
River levels rose with very little warning, reaching a peak within minutes or hours
Very destructive and can cause loss of life
12:30 - Heavy rain began to fall
12:39 - Flood warning issued
17:00 - Floods reach peak, cars swept away
17:10 - Major incident declared
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What was the impact?
Up to 1,000 people had to be evacuated from their homes
20 accomodation providers forced to shut down (Bostcastle's economy is 90% reliant on tourism)
58 properties were flooded, 4 demolished
4 footbridges along Vallency Valley washed away
84 wrecked cars
Roads blocked by flood water
£2 million in damage - no fatalities
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What were the causes? (Heavy rain)
1. Heavy rain falls on waterlogged ground
2. Rainfall unable to soak in, so runs into river
3. River rises dramatically, bursting its flood valley floor
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What were the causes? (Steep-sided valleys)
The steep sided valleys that converge down to the sea, known in the trade as “flashy catchments”, act as huge funnels and can produce true flash floods after a sudden cloudburst or prolonged heavy rainfall
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What were the causes? (Slatey impermeable rocks wi
The cause was the combination of
•intense convectional rain,
•local topography and
•the geology
resulting in a flash flood
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How is the impact of future floods being reduced?
Control/restrict developments on flood plains
Build bigger culverts on both rivers
Build embankments and strengthen natural levees
Afforestation (plant more trees)
Flood control Dam (hold back rainwater and release it slowly)
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