Watch Movies2Watch. A look at two of the worst flash floods in British history, which were separated by exactly 52 years, featuring interviews with survivors, rescuers, politicians and experts. On August 16th, 1952, 15cm of rain fell in just a few hours on Lynmouth in Devon, cascaded into the village via the East and West Lyn rivers, bringing with it 114,000 tons of boulders, sediment and uprooted trees that smashed into buildings. 52 years later, on August 16th, 2004, Boscastle in Cornwall suffered four hours of relentless rainfall, which funnelled down the steep banks of the valley from the moors above the port.