Uncovering ancient flood records reshapes understanding of extreme events

Uncovering ancient flood records reshapes understanding of extreme events
by Sophie Jenkins
London, UK (SPX) Apr 01, 2025

Recent research led by the University of Exeter reveals that floods regarded as "unprecedented" in recent decades are overshadowed by far more severe events found in ancient records. By studying palaeo-flood data from western Europe, scientists have shown that many floods in the distant past were significantly more extreme than any seen in recent history.

Drawing on evidence preserved in floodplain sediments and geological formations, the researchers examined flood activity spanning thousands of years. Their findings challenge assumptions based on modern river gauge data, which typically extend back less than a century.

While recent floods in regions like Pakistan, Spain, and Germany have caused catastrophic damage and loss of life, the study indicates that such events are not without historical precedent. "Such floods are seen as 'unprecedented' - but if you look back over the last few thousand years, that's not the case," said Professor Stephan Harrison of the Department of Earth and Environmental Sciences at Exeter's Penryn Campus. "In fact, floods we call unprecedented may be nowhere near the most extreme that have happened in the past."

The team underscores the importance of incorporating palaeo-flood evidence into flood risk assessments, especially as climate change introduces new layers of complexity. Professor Harrison noted, "You need that knowledge of the past if you're going to understand the present and make predictions about the future. Coupling evidence of past extremes with the extra pressure now being added by human-caused global warming - which causes more extreme weather - you see a risk of genuinely unprecedented floods emerging."

Professor Mark Macklin added that relying solely on short-term datasets limits the accuracy of flood frequency estimates. "If we rely on relatively short-term records, we can't say what a 'one-in-200 year' flood is - and therefore our resilient infrastructure may not be so resilient after all," he explained. "This has profound implications for flood planning and climate adaptation policy."

The study analyzed palaeo-flood records in three major regions: the Lower Rhine (Germany and Netherlands), the Upper Severn (UK), and rivers near Valencia (Spain). In the Lower Rhine, data from the last 8,000 years reveal at least 12 flood events likely to have exceeded present-day magnitudes. Meanwhile, the Upper Severn's 4,000-year record shows that floods recorded in the last 72 years are relatively minor by comparison. The most powerful flood identified there occurred around 250 BCE and may have produced a peak discharge 50% greater than the severe flooding seen in 2000.

Research Report:Robust climate attribution of modern floods needs palaeoflood science