Floods in Grimma, Germany, on 3 June 2013
JENS WOLF/DPA/AFP via Getty Images
The years 1990-2016 rank among the worst periods of flooding in Europe in five centuries, according to an assessment of historical letters, annals and legal records.
The period has seen intense floods such as those in England in 2009 and 2002’s devastating flooding in Dresden in Germany, Prague in the Czech Republic and across central Europe. However, a lack of detailed data beyond the past 50 years has left it unclear whether we are living through a particularly flood-rich period.
Günter Blöschl at the Vienna University of Technology in Austria says we are. Over seven years, his team built an unparalleled database of 103 rivers across Europe by scouring chronicles and other written records. Legal records proved reliable sources, including those from annual “beating the bounds” in England and Wales, where a church leader walked around a parish to record boundaries and often noted floods.
“We’ve almost exclusively used original sources. Second-hand information is much more accessible but it’s also less accurate,” says Blöschl. The descriptions were used to class 9576 floods as notable, great or extraordinary, in order to measure flood-rich periods – when floods were bigger in extent and frequency than average – since 1500.
The database revealed that 1990 to 2016 was the third most flood-rich period, behind 1840 to 1880 and 1750 to 1800, which was at number one. Blöschl says each one could move up or down a position in the rankings if the analysis was tweaked, due to patchier records in some years and places. Data is relatively scant for Scandinavia, for example, and the team ended their analysis at 2016.
The most recent period is markedly different to older ones. Most of the past flood-rich periods were associated with cooler temperatures, but the current one comes amid a backdrop of climate change-driven warmth. Blöschl believes storms shifting northwards are to blame. More of the recent floods have also been in summer than past flood spells – 55 per cent versus 41 to 42 per cent – driven largely by more summer floods in central Europe.
According to the team’s analysis, the period 1900 to 1990 was relatively disaster-free, which is why the recent floods have taken many people by surprise. “People forgot the extent and frequency of floods that may occur,” says Blöschl. “They had a false sense of security.”
Journal reference: Nature, DOI: 10.1038/s41586-020-2478-3
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