Traditional flooding research primarily focuses on understanding hydrological and engineering aspects, but a paradigm shift towards a more holistic approach has emerged. This new perspective recognizes that water systems are dictated by complex processes with far-reaching social, environmental, and economic implications. This study analysed long-term rainfall variability for the European region in the 20th century, a topic of important significance in the context of a changing climate and current predictions. The analysis of the changing dynamics of precipitation patterns and the increase of the intensity of precipitation events, profoundly influences the mitigation strategies of a resilient future and thus has profound implications.
The changing rainfall distributions have a clear influence in the frequency and the magnitude of precipitation events, exacerbating the risk of flooding and flash flooding (Sassi et al., 2019; European Environment Agency, 2017). The NatCatSERVICE database (European Environment Agency, 2017) reported that the number of climatic extreme events increased from 80 per year in 1980–2013 to 120 in 1990 (50% increase) and to 140 in 2000. The HANZE dataset (Paprotny et al., 2018) has analysed 1564 natural hazard events between 1870 and 2016 with a particular focus on flood occurrences. In Southern, Central and Western Europe most floods occur predominantly in the summer. In southern Europe, flash floods were found to be the most common type of flood, whilst in central and western Europe, river floods were more frequent than other types of flooding. In contrast, in northern Europe, floods were mainly caused by snowmelt and generally resulted in fewer significant losses (Paprotny et al., 2018). This is in agreement with the intensification of rainfall events which is shown across Europe in our summary figures (Figs. 5 and 3).
The study analysed the rainfall distribution data using the region of Europe as a case study and looking specifically at the four UN regions: Northern Europe, Eastern Europe, Southern Europe, and Western Europe. Despite regional variations in the impact of rainfall, a discernible overall increase in % of days with changes in rainfall is evident across all four regions which agrees with current research findings, confirming heavy precipitation has intensified since 1950 (European Environment Agency, 2017). The two frameworks presented similar long-term changes in the rainfall variation.
In the stagnant comparison framework, the long-term rainfall change in all regions is presented by the change detected in the final comparison period (2005–2020). This change is also detected using the moving comparison method; however, the change is identified as occurring much earlier on in the first comparison period (1960–1980). The change was also confirmed when investigating which of the distribution bins changed the most, the number of 0-5mm rainfall days (dry days) over the European regions. In each of the periods of high difference using both methods, a matching decrease in the number of 0-5mm rainfall days was also observed indicating the highlighted changes in rainfall are an intensification of rainfall days over land which is again in agreement with the HANZE project outcomes (Paprotny et al., 2018).
In line with the evidence, the European Environment Agency and the Intergovernmental Panel on Climate Change (IPCC) emphasise that short-duration (sub daily) rainfall extremes are intensifying in frequency and magnitude due to the effects of climate change (European Environment Agency, 2017; Fowler et al., 2021; IPCC, 2022). The two frameworks presented in this research highlight complimenting approaches to identifying the magnitude and timing of rainfall variation. This approach is flexible and can be applied to a variety of resolutions and use-cases.