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Boscastle Flood, August 2004 - Coggle Diagram
Boscastle Flood, August 2004
Hydrographs
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It shows rainfall and discharge - the volume of water flowing a river measured in meters cubed per second (cumecs). Lag time shows how quickly water is transferred into the river channel. The shorter the lag time, the greater risk of flooding.
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Where is it?
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The village is downriver of the confluence of 3 rivers, the Paradise, the Jordan and the Valency
What happened and why
The drainage basin of Boscastle is steep with areas of impermeable rock such as slate or granite, which leads to high levels of run-off and causes river levels to rise rapidly during periods of heavy rainfall.
In 2004, very heavy rainfall caused the rivers upstream of Boscastle, the Jordan and the Valency, to overflow.
Due to the steep valleys surrounding Boscastle and the already soaked ground, a large amount off water funnelled straight down into the town.
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in 2004, the town and surrounding area had already had loads of rain - this mean the ground couldn't soak up ANY water.
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Over 1,422 million litres of rain fell in just two hours. This is equal to 21 petrol tanker loads of water flowing through Boscastle every second!
Together with tree trunks and large branches, cars acted like battering rams smashing into bridges and buildings.
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