August 10, 2017

expert reaction to study looking at climate change and flooding in Europe

A new study published in the journal Science looks at climate change and river flooding in Europe.

Dr J Iwan Jones, Research Leader, River Communities Group, Queen Mary University of London, said:

“The work published by Blöschl and colleagues is a thorough and careful analysis of the effects of changing climate on river flooding.  The risk of flooding, and the associated human cost, is expected to increase with climate change.  However, the occurrence and magnitude of floods is dependent on more than just rainfall, which has hampered attempts to detect patterns of change.  Here, Blöschl and colleagues have analysed high quality flood records from more than 4,200 riverine gauging stations across 38 European countries to determine change in the timing of peak flows over the last five decades, a more sensitive and robust measure of change than the size or frequency of floods, and found marked change in peak flows across Europe.  They have also explored the potential mechanisms behind the changes.  Snow is melting earlier in the cold areas of North Eastern Europe, and the Alps and Carpathian mountains, leading to earlier spring floods in these regions.  In the Atlantic coast of Western Europe, autumn floods are occurring earlier as soils become saturated by increased autumn rainfall.  Yet, around the North Sea and in parts of southern Europe changing weather patterns are the most likely cause of later winter floods.  Although translating such changes in flood-generating mechanisms into future patterns of severe flooding is not straightforward and will require further research, this work indicates clear shifts in the vital signs of flood regimes.

“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.

“The work of Blöschl and colleagues shows just how important long-term monitoring networks are.  Using river gauging stations networks, they have demonstrated marked changes in the timing of floods across Europe.  If we are to understand the implications of climate change for the natural environment, more research effort should be put into long-term ecological networks.”

Prof Christopher Joyce, Professor of Ecology, University of Brighton, said:

“The press release is an accurate interpretation of the science in the paper.

“The study is based on data from over 4,200 hydrological stations across Europe over a period of 50 years, and is a comprehensive evaluation of river flooding patterns.  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.”

Prof Mark Maslin, Professor of Climatology, UCL, said:

“Nearly every major city and town in Europe is built on a river and we protect this urban infrastructure by using past floods as a gauge of the potential risk.  The study by Blöschl et al in Science shows that this approach underestimates the risk as climate change has made European floods occur earlier in the year increasing their potential impact.  This means all the infrastructure that we have built to protect our cities needs to be reviewed as much of it will be inadequate to protect us from future climate change induced extreme flooding.  In the UK a systematical check on our urban flood defenses is required based on this new study to ensure the extensive damage of 2007 and 2010 floods are avoided.”

Prof David Schultz, Professor of Synoptic Meteorology, School of Earth and Environmental Sciences, University of Manchester, said:

“The authors are to be applauded for the hard work of synthesizing the river-flood record across Europe.  Assembling this dataset is a big contribution to our understanding of how weather and climate affect floods.  Unfortunately, applying a simple trend analysis over 50 years when many of the regions show interesting variations across the decades is problematic.  What they call Southern England is really a box with corners approximately of Dorset, Hampshire, Derbyshire, and Flintshire, and does not include London and the southeast.”

* ‘Changing climate shifts timing of European floods’ by Günter Blöschl et al. will be published in Science at 19:00 UK time on Thursday 10 August 2017, which is also when the embargo will lift. 

Declared interests

Dr J Iwan Jones: “Dr Jones is employed by Queen Mary University of London.  He receives funding from Defra, Environment Agency, Scottish Environmental Protection Agency, Northern Ireland Environment Agency, Natural Resources Wales – these organizations maintain and own the gauging station network which supplied part of the data used, although they are not involved in the publication.  Dr Jones previously worked with the NERC Centre for Ecology and Hydrology, who employ two of the authors, Jamie Hannaford & Shaun Harrigan, although not with these two individuals.  He is a member of the British Ecological Society.”

Prof Christopher Joyce: “Professor is employed full-time by the University of Brighton. He is a member of the British Ecological Society, Royal Geographical Society and Society of Wetland Scientists.”

None others received.