Flood-rich periods in the last 500 years in Europe

Abstract:

We analyse the flood history of Europe using a new database composed of 103 high-resolution (sub-annual) historical flood series based on contemporary sources ranging from diaries and chronicles to economic and legal administrative records, correspondence and newspapers, among others. The historical flood time series consist of a three-scaled index of flood magnitude (notable, class 1; great, class 2; and extraordinary flood, class 3) and the time of the year when the floods occurred. We interpolate the flood magnitudes in space and time accounting for observation bias and identify nine flood-rich periods and associated regions (Figure). Among the periods richest in floods are 1560–1580 (western and central Europe), 1760–1800 (most of Europe), 1840–1870 (western and southern Europe) and 1990–2016 (western and central Europe). In most parts of Europe, previous flood-rich periods occurred during cooler-than-usual phases, but the current flood-rich period has been much warmer. Flood seasonality is also more pronounced in the more recent period. For example, during previous flood and interflood periods, 41 per cent and 42 per cent of central European floods occurred in summer, respectively, compared with 55 per cent of floods in the recent period. The study suggests that the present European flood-rich period is indeed exceptional from a long-term perspective.

Figure: Flood-rich periods in Europe in the past 500 years. Periods are coloured by their rank, with red (period Va) indicating the strongest and blue (period VIII) indicating the weakest period. (from Bloeschl et al., 2020, Nature, doi:10.1038/s41586-020-2478-3).