Climate change is having an impact on river flooding in Europe, according to a new study published in the journal Nature this week.

An example of the relatively new area of ‘climate attribution’, which looks at links between human-driven climate change and impacts on weather or other climatic events, the new research suggests that climate change has affected the timing of river flooding in Europe over the past 50 years.

The data, gained from observations at over 4,000 measuring stations, show that around the north sea (the area including Scotland), winter floods have been delayed by up to 8 days. In southern England, floods have moved forward by more than two weeks (15 days).

In all, warmer temperatures have led to earlier floods in northeastern Europe, due to earlier spring snowmelt; around the North Sea and parts of the Mediterranean, delayed winter storms (linked to warming at the planet’s poles) have led to later winter floods; in Western Europe (including the Atlantic coast from Portugal to England), winter floods are also occurring earlier now, due to soil moisture levels reaching maximum capacity earlier in the year.

The researchers said that the most marked change is the pattern of earlier floods linked to warmer temperatures and earlier snowmelt in Scandinavia, but that there is a “clear climate signal in flood observations at the continental scale.”

Researchers behind the report expressed concerns that changes to seasonality in floods could also affect their severity, meaning flood risk management will have to adapt differently in different parts of Europe. They said their findings could have impacts for aquatic life, including altering the breeding season of different fish species, and could impact on farming in a number of ways.

Discussing the potential impacts, Dr J Iwan Jones from Queen Mary University, London, who wasn't involved in the research, said, “Whilst these changes in our weather have severe implications for agriculture and human infrastructure, they are likely to cause pronounced change in the natural environment too.  Flow is one of the most important factors in river ecosystems.  The life cycles of many aquatic organisms are timed to coincide with changes in the flow in the rivers they inhabit.  If floods happen at the wrong time, it will affect their populations: timing is everything.  For example, salmon can only access the headwaters where they breed if peak flows occur when they are ready to move.  Young of the year may not have grown enough to be able to cope with floods if they happen too early.

“Changes in weather patterns due to climate change are likely to deliver substantially more diffuse pollutants into rivers, further impacting our natural flora and fauna.”

Also reacting to the findings, Prof Christopher Joyce, Professor of Ecology, University of Brighton, said, “The paper acknowledges that proving a causal link between changing climate and flood patterns is problematic given land-use changes and river engineering over recent decades.  Nevertheless, the results are interesting, important and consistent with many regional climate change predictions. 

“Changes in flood timing can have significant ecological implications for floodplains, especially if the shift towards later flooding delays it into the growing season.  This affects plant development, including flowering, and therefore the composition of floodplain vegetation, which is of great value for agriculture and nature conservation.”