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New index reveals recent floods could signal climate change

Long-term records suggest that recent flooding in the south of England could indeed signal the onset of climate change.

A new flood index enables widespread flooding and weather patterns to be viewed in the context of the last 150 years, revealing that four of the six most severe flood episodes since 1871 have occurred in the last 30 years.

The Fluvial Flood Indices were developed by Professor Rob Wilby at Loughborough University with Associate Professor Nevil Quinn at the University of the West of England and Dr Colin Harpham at the University of East Anglia.

The indices match weather patterns and river flow data collected over the last 60 years to reconstruct likelihood of widespread flooding in Britain back as far as the 1870s. The index is broken down by British region and updated weekly from atmospheric pressure data.

Professor Wilby, a Hydroclimatic Modelling specialist in Loughborough University’s Department of Geography, said:

“Until now we’ve largely based our view of flood risk on relatively short river flow records, but our flood index goes back nearly 150 years, helping us place recent extreme weather in a much longer context.”

The indices reveal that the sequences of weather leading to the recent floods in southern England occur on average once every 25 years. The worst flooding suggested by the series happened in 1872, with later flood-rich episodes in the 1950s, 1980s and 2000s.

Professor Wilby added:

“The extraordinary events in 1872 show the extent to which flood severity varies from one decade to the next. This flooding was so significant it was even captured in a painting by Monet.

“However, to experience four of the six most severe episodes in the last 30 years is disconcerting. Such a flood-rich period in the context of a 144-year record is very unusual and linked to the large number of cyclones passing over the country.”

In 2008, Professor Wilby and Professor Hayley Fowler at Newcastle University predicted that the first signs of climate change could be detectable in winter rainfall records for Southwest England as early as the 2020s. Recent events in Somerset are consistent with this view.

It is envisaged the indices could be used by researchers and agencies interested in tracking long-term changes in weather patterns linked to widespread flooding. The flood indices can be accessed online