Climate change disrupting river flooding patterns, scientists warn

Climate change is disrupting patterns of river flooding and spring growing across Europe, raising concerns about the effect on the landscape, according to scientists.

A study of five decades of flood and temperature data found the thermal growing season – periods when the temperature rises consistently above 5C, encouraging plants and trees to begin to grow – has been consistently starting earlier in the year.

It brings the growing season closer to the periods when the highest river floods occur, which have begun to happen later in the year in central and eastern Europe.

Researchers from the University of Glasgow and Umea University in Sweden said the analysis demonstrates for the first time an increasing overlap between the onset of spring and the highest points of seasonal flooding.

Lead author Dr Thorsten Balke, of Glasgow’s School of Geographical and Earth Sciences, said: “The changes we’re seeing are actually quite drastic – there’s a clear pattern of flooding occurring more regularly in the growing season.

“That raises a lot of questions about the effect that might have on the European landscape.

“There’s a lot of interaction between the rocks and soil and sediment on the banks of rivers and the trees and plants which grow there, which plays into how floods are controlled and the effect they have on the landscape around them.”

He added: “Now that floods are happening more regularly during growing season, their waters are encountering a lot more vegetation like seedlings and larger trees and carrying them downstream.

“That not only strips away potential food sources for local wildlife, it also causes more of what we call ‘hydraulic roughness’ which affects how the flood moves.

“It could make the flood move more slowly so that it affects areas of land which weren’t flooded in previous years, with knock-on effects on farming, for example, or in property damage within the floodplain.

“It could also change the shape of the rivers themselves, for example where river banks are no longer protected flooding if seedlings fail to establish in the growing season.”

The paper, Increasing Synchrony of Annual River‐Flood Peaks and Growing Season in Europe, is published in the journal Geophysical Research Letters.