<P> The torrential rain led to a 2 m (7 ft) rise in river levels in one hour . A 3 m (10 ft) wave, believed to have been triggered by water pooling behind debris caught under a bridge and then being suddenly released as the bridge collapsed, surged down the main road . Water speed was over 4 m / s (10 mph), more than enough to cause structural damage . It is estimated that 20,000,000 cubic metres (5.3 × 10 US gal) of water flowed through Boscastle that day alone . The steep valley sides, and the saturated surface ensured a high amount of surface run - off . </P> <P> Changes in farming practice in the area also possibly contributed, sewage could have been a cause as well, with a reduction of trees and hedges higher up the valley causing water to flow through more quickly than would have been the case in the past . Fortunately, no one died in the flood . </P> <P> 75 cars, 5 caravans, 6 buildings and several boats were washed into the sea; approximately 100 homes and businesses were destroyed, and some had to be demolished; trees were uprooted and debris were scattered over a large area . In an operation lasting from mid-afternoon until 2: 30 AM, a fleet of 7 Westland Sea King helicopters rescued about 150 people clinging to trees and the roofs of buildings and cars . No major injuries or loss of life were reported . The estimated cost of damage was £ 15 million . </P> <P> Most work takes place in the winter season (October--May), during the off - season . The carpark is reduced to half the space (120 spaces) in winter, for works to take place, and then back to 240 spaces in summer . </P>

How much did it cost to repair boscastle after the flood