This Christmas the people in Cockermouth are clearing up after the 1 in 100 year flood caused by Desmond with a very bitter taste in their mouth. They were told that the last flood was a 1 in 100 year event ... And that was in 2009.
'More or Less' is a great little radio programme on the World Service that tries to explain colloquial expressions and news stories that involve numbers. In this episode they explain 1 in 100 year floods well.
Click Here: http://www.bbc.co.uk/programmes/p0396yn5#play