One of the most devastating floods and peacetime rescue operations took place in the small Cornish village of Boscastle.
The village flooded in August 2004, washing cars and buildings into the sea and putting peoples' lives in danger.
Over 60 mm of rainfall (typically a month's rainfall) fell in two hours. This led to a flash-flood event.
The ground was already saturated due to the previous two weeks of above average rainfall.
The drainage basin has many steep slopes, and has areas of impermeable slate causing rapid surface run-off.
Boscastle is at the confluence of three rivers - Valency, Jordan, and Paradise.
A large quantity of water arrived within a short space of time causing the rivers to overflow.
The flooding coincided with a high tide, making the impact much worse.
Many tourists were in Boscastle during the day, as it was the middle of the summer holidays. This meant that a higher than normal number of people needed to be evacuated.
The old road bridges became a major obstacle to debris transported by the river.
|Physical causes of the Boscastle flood||Human causes of the Boscastle flood|
|Rain for 12 out of 14 days in August.||Many trees had been cut down for farming. This limited interception and water went straight into the river channel.|
|A depression brought a thunderstorm on 16 August with over 200mm of rain in 24 hours.||Increase in buildings within the drainage basin meant that there were more impermeable surfaces which directed water back to the river faster.|
|Steep valley sides - water flowed into the river channel very quickly.||A few old arch bridges got blocked up with the flood debris. The bridge acted like a dam and eventually smashed through causing a surge of water up to 5m high.|
|The rock in the local area is slate which does not allow percolation.|
|The soils were quite thin and made up of impermeable peat soils. These became saturated so water became surface run-off very quickly.|
|There were very few trees to absorb water and slow the amount of water going into the river.|
Once the water had receded, the extent of the damage became clear. More than 70 vehicles were washed downstream by the flash-flood in Boscastle.