Climate change significantly impacting floods by making them increasingly severe

A recent study, which analyzed river flow data from thousands of locations across Europe over 50 years, provides the most definitive evidence yet of the link between climate change and flooding


                            Climate change significantly impacting floods by making them increasingly severe

Floods are becoming more severe, owing to human-induced climate change. A multinational research team, which looked at river flow data from thousands of locations over a 50-year period, provides the clear evidence that climate change also controls the magnitude of floods, with parts of northern Britain seeing the largest increase in intense floods in Europe.

“Flood events are becoming increasingly severe in north-western Europe, including the UK,” according to the findings published in Nature.

Scientists have long suspected that climate change might have an impact on the severity of floodwaters because a warmer atmosphere can store more water, although this is not the only factor behind flood changes in a warming world. However, until now, it has not been clear how and to what extent climate change influences the magnitude of floods as there were no ‘apparent’ patterns. 

“We already knew from our previous research that climate change is shifting the timing of floods within a year. But the key question is: Does climate change also control the magnitude of flood events? So far, the available data had not been sufficient to ascertain whether this is the case or not. We have now examined this question in great detail and can say with confidence: Yes, the influence of climate change is clear,” says lead author Professor Günter Blöschl from the Vienna University of Technology.

Overflowing rivers can cause massive damage, and globally, the annual damage caused by river floods is estimated at over 100 billion dollars. Scientists have warned that these numbers from flood damage will continue to rise, along with the devastating impact on communities.

For the study, researchers examined data from 3,738 flood measurement stations in Europe from 1960 to 2010. The study was led by the Vienna University of Technology and involved nearly 50 scientists from 35 institutions in 24 European countries, including the Centre for Ecology & Hydrology (CEH); the University of Bath; and the University of Liverpool from the UK.

Findings reveal significant regional differences

While changes in the magnitude of flood events observed in recent decades can be attributed to climate change, it does not have the same effect on floods everywhere, shows analysis.

The researchers found that in central and north-western Europe, between Iceland and Austria, floods are increasing because precipitation (rain, snow, sleet or hail) is increasing and soils are becoming wetter. In southern Europe, on the other hand, flood levels are decreasing, as climate change results in declining precipitation, and the higher temperatures cause increased evaporation of water in the soil. 

Pictured above is the flooded Lyth Valley in Cumbria after Storm Desmond in December 2015. (Center for Ecology & Hydrology or CEH)

However, in Mediterranean areas, for small rivers, floods may be becoming larger due to frequent thunderstorms and land management changes such as deforestation. In the more continental climate of Eastern Europe, flood levels are also decreasing, which is due to shallower snowpacks in winter associated with the higher temperatures. 

“Processes differ across Europe - but the regional patterns all correspond well with predicted climate change impacts. This shows us that we are already in the midst of climate change,” says Blöschl.

The magnitude of the changes, according to the scientists, is also ‘remarkable.’ The variation ranges from an 11.4% increase per decade in flood levels in northern England and southern Scotland to a 23.1% decline per decade in parts of Russia. 

The researchers warn that if these trends continue into the future, major effects on flood risk can be expected in many regions of Europe. According to the team, the increase in flood magnitude is part of a continent-wide pattern of changes in flooding, which is in line with what one may expect in a warming world. This, say the researchers, highlights the importance of long-term hydrological monitoring and the benefits of data sharing and collaboration at a European scale to understand the mechanisms behind observed changes in flooding better.

Stating that policymakers must adapt to the realities of a changing climate and the associated flood risk, the research team recommends the inclusion of their findings in flood management strategies. 

“Regardless of the necessary efforts of climate change mitigation, we will see the effects of these changes in the next decades. Flood management must adapt to these new realities,” says Blöschl. 

Dr. Thomas Kjeldsen from the University of Bath, one of the co-author's of the study, adds that incorporating the evidence of increasing flood risk into engineering design and general flood management would ensure “we are better prepared for future changes - a point also raised in the government’s national flood resilience review.”

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