An analysis of five decades’ worth of figures found that climate change is altering the timing of river flooding across Europe.
The results, published in the journal Science, reveal that rivers are flooding earlier in the spring in the western and north eastern parts of the continent, and later in the season around the North Sea and some sectors of the Mediterranean coast.
River flooding affects more people worldwide than any other natural hazard.
Professor Günter Blöschl, of Vienna University of Technology in Austria, and his colleagues analysed data collected from more than 4,200 hydrometric stations in 38 European countries between 1960 and 2010.
They also compared rainfall, soil moisture and temperature figures to explore potential drivers of flood changes.
Prof Blöschl said: “The most substantial changes occurred in western Europe along the North Atlantic coast from Portugal to England, where 50 per cent of the stations recorded a shift toward earlier floods by at least 15 days over the 50-year period.”
The researchers attributed the shift largely to the nature of soil – in particular, its ability to retain moisture – in the region.
Prof Blöschl said: “Nearly all stations in north eastern Europe recorded a shift to earlier flooding as well, with about half finding the shift to exceed eight days; these changes are largely due to increases in snowmelt that occur in a warmer climate.
“Around the North Sea, about half of the stations recorded a shift toward later flooding by more than eight days.”
Flooding expert Dr Louise Slater, of Loughborough University said of the findings: “Without adaptations, such changes in flood seasonality can profoundly affect agricultural yields, infrastructure safety and operation, hydropower production, water supplies, and water management.
“The study thus prompts important questions about flood predictability.”