Millennial scale variability in high magnitude flooding across Britain

Abstract

Abstract. The last decade has witnessed severe flooding across much of the globe, but have these floods really been exceptional? Globally, relatively few instrumental river flow series extend beyond 50 years, with short records presenting significant challenges in determining flood risk from high-magnitude floods. A perceived increase in extreme floods in recent years has decreased public confidence in conventional flood risk estimates; the results affect society (insurance costs), individuals (personal vulnerability) and companies (e.g. water resource managers – flood/drought risk). Here we show how historical records from Britain have improved understanding of high magnitude floods, by examining past spatial and temporal variability. The findings identify that whilst recent floods are notable, several comparable periods of increased flooding are identifiable historically, with periods of greater frequency (flood-rich periods) or/and larger floods. The use of historical records identifies that the largest floods often transcend single catchments affecting regions and that the current flood rich period is not exceptional.