Frequency analysis of extreme rainfall in Cumbria, 16–20 November 2009

Abstract

Towards the end of November 2009, west Cumbria in northwest England experienced severe flooding which caused extensive damage and disruption throughout the region. The flooding was triggered by an exceptional rainstorm during which a record 316.4 mm of rainfall was recorded at Seathwaite Farm, Borrowdale over the 24-hour period up to 00:00 on 20th November. Drawing on the results of a recent project which has developed a new model of point rainfall depth-duration-frequency (DDF) for the UK, return periods are estimated for the highest point rainfall observations available for the Cumbrian event and compared with frequency estimates derived from the Flood Estimation Handbook rainfall model (Faulkner 1999). The spatial and temporal characteristics of the storm event are examined using data from the Environment Agency's raingauge network. For the two most affected rivers, the Derwent and the Leven, return periods of catchment rainfall are estimated for durations up to 96 hours.