River flooding: area simultaneously affected in EU has grown by 50% in past 50 years …… This scale grew more in certain regions, including the British-Irish Isles, parts of Germany, Belgium, The Netherlands ……….

River flooding costs billions of euros annually in the EU. When one river floods, others nearby often do so at the same time — extending the overall impact beyond the border of an individual drainage basin. With this in mind, this study analysed the spatial extent of flood events across Europe from 1960 to 2010, using data from the European Flood Database (EFD). The research presents key findings for flood forecasting, risk financing and flood-mitigation policy.

Landscape and weather conditions in Europe lead to flood events involving multiple drainage basins — and sometimes multiple countries — simultaneously. Such large-scale flooding can significantly affect the societies that inhabit these areas, and bring huge financial costs. However, such events have not been systematically analysed at the continent scale in Europe. This study used data from the European Flood Database (EFD) to analyse the spatial extent of flood events across Europe from 1960 to 2010, spanning over 4 000 river basins. The researchers looked for trends over time and across Europe, to establish if there is any correlation with landscape features and recurrent climatic oscillations such as El Niño. The study applied a measure known as the ‘flood synchrony scale’ to the data — the maximum radius around an individual river gauge, within which a minimum of 50% of the other river gauges recorded flooding within a seven-day period. The researchers calculated ‘mean flood synchrony scales’ for individual stations by averaging annual flood synchrony scales over time. The same calculation was used for rainfall data, for which the study calculated ‘precipitation synchrony scales’. Click here to read more