“Boscastle: The village washed on to the map”

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Boscastle – “Washed on to the map” What are we learning today ? Key questions Where is Boscastle? What caused the flooding? What were the primary effects of the flooding?

Two key terms Primary effects Flash flood Effects that happen as a DIRECT RESULT of the flooding e.g. “trees ripped from the ground” A sudden local flood that often happens due to intense rainfall and happens over around 8 hours

Where is Boscastle? A small town on the north coast of Cornwall. 30 kms north west of Plymouth.

CAUSE 1: VERY HEAVY RAIN Most of the rain fell in a five hour period Peak intensities were in excess of 30mm/hr (0.5mm per minute) A month’s rain fell in just 2 hours

CAUSE 2: THE STEEP SIDED VALLEYS

CAUSE 3 – SLATEY IMPERMEABLE ROCKS with CLAY SOILS The cause was the combination of intense convectional rain, local topography and the geology = resulting in a flash flood no one could have predicted.

12.15 Rain gauge at nearby Lesnewth some 4km (2½ miles) up the valley, shows no rainfall and it is dry in Boscastle’s harbour area, yet there are torrential showers at Camelford and at the top of Boscastle. What happened?

16.00 a 3 metre wall of water runs through Boscastle car park at 40 mph.

17.00 Rescue Helicopters. In an operation lasting from mid-afternoon until 2:30 AM, a fleet of seven helicopters rescued about 150 people clinging to trees and the roofs of buildings and cars. Amazingly, no major injuries or loss of life were reported.