Storm surge prediction in the Bristol Channel—the floods of 13 December 1981

Abstract

A secondary depression crossing southern Wales and England on the 13 December 1981 resulted in the highest water levels experienced in the Bristol Channel this century and severe flooding along the north Somerset coast. Both a numerical model-based prediction scheme and the Lennon (1963, Quarterly Journal of the Royal Meteorological Society, 89, 381–394) criteria for west coast storm surges failed to provide adequate warning of the expected levels. A numerical reconstruction of the event shows that the failure of the surge model forecast was due to an incorrect prediction by the atmospheric model used to provide the meteorological input to the sea model. The fallibility of the Lennon criteria suggests their reappraisal, particularly in the light of a subsequent failure in November 1984. Some of the difficulties in the identification of storm surge residuals within the Bristol Channel are shown to be associated with tidal measurement and prediction problems which are, as yet, unresolved.