The little town of Boscastle is lying on a natural harbour, and in a narrow valley. This position is both a blessing and a curse, since this is why it is one of the most popular tourist destinations, but on the other side it was hit, after heavy rain, by a flash flood in August 2004. Luckily there were no fatalities, but a few livelihoods were ruined.
A lot of small villages in Cornwall are in a similar situation, some of them have had flood control basins installed.