Flash Floods in the Cornish Village of Boscastle
All About the Flooding of North Cornwall, UK, in August 2004
Aug 8, 2009
Despite heavy rains on that unforgettable day, no one expected to see a huge foaming wall of water to come rushing down the valley into the quaint little village of Boscastle in Cornwall. It was the worst flooding ever seen in the area.
Devastation in Boscastle
The traditional harbour village of Boscastle is designated an area of outstanding natural beauty. Situated on the North coast of Cornwall within the UK, Boscastle is perched on the edge of a thin peninsula looking out onto vast stretches of the North Atlantic. It is one of the warmest and wettest places in the British Isles. But on Friday, August 16, 2004, this peaceful village was devastated by a roaring torrent of water ten feet high. This unexpected event had been triggered by localised and intense rainfall of 2.5 inches (625 mm) in just 2 hours whilst the ground was already at saturation point (“Devastation in Boscastle” BBC online report, 23 August 2004).
The History of Flooding in South West England
Eerily, this monstrous flash flood occurred almost 52 years to the day after a catastrophic flood in Lynmouth, Devon, a few miles north of Boscastle. Lynmouth’s devastation occurred on Friday, August 15, 1952 and left 34 people dead.
Floods are no stranger to Boscastle, having occurred in the years 1950, 1958, 1963, 1968 and 1981. But the flash flood of 2004 was different for its unusual ferocity and huge volume of water. People had to be airlifted to safety and over 70 houses were ruined. Local bridges had also been breached and cars swept out to sea. But unlike Lynmouth, there had fortunately been no fatalities.
The Causes of the Flood
August in England is statistically the second warmest month of the year after July. But August 2004 was one of the warmest and wettest on record. The unusually high rainfall and the causes of Bocastle’s flooding were put down to:
- The sluggish movement of heavy frontal systems
- Persistence of a moist subtropical air mass over South West England
- Several hurricane remnants drifting over Britain via the Gulf Stream, notably hurricane Alex
- Boscastle’s position at the bottom of a narrow valley
- The ground reaching saturation point after exceptionally high rainfall in August
- Slow moving thunderstorms on the day of the flood
- The damming effect of debris and local bridges causing the floodwater to build up and to surge suddenly down the valley
Rainfall in Boscastle
Rainfall leading up to the Boscastle flooding had been exceptionally high within a highly-focussed area, recording 7.8 inches (200.4 mm) within a 24 hour period. (Extreme Floods – A History in a Changing Climate, Robert Doe Sutton Publishing, 2006). By contrast, there had been little rain elsewhere during the day and beaches were well populated. As South West England had already received much rain for August, the ground was at saturation point. The thunderstorms that hit the area proved too much for the usual channels and having nowhere else to go, the water cascaded down into the valley towards Boscastle.
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