EGU24-5997, updated on 08 Mar 2024
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Surprising megafloods in Europe – learning from the big picture

Miriam Bertola1, Günter Blöschl1, and the Team members*
Miriam Bertola and Günter Blöschl and the Team members
  • 1Vienna University of Technology, Institute of Hydraulic Engineering and Water Resources Management, Wien, Austria (
  • *A full list of authors appears at the end of the abstract

Megafloods that far exceed previously observed records at a given location can take citizens and flood managers by surprise. Existing methods based on local and regional information rarely go beyond national borders and cannot predict these floods well because of limited data on megafloods, and because flood generation processes of such extremes differ from those of smaller, more frequently observed events. Here we analyse the most comprehensive dataset of annual maximum discharges in Europe available to date, to assess whether recent locally surprising megafloods could have been anticipated using observations in hydrologically similar catchments across the continent.

We base our analysis on annual maximum river discharge observations from 8023 gauging stations for the period 1810–2021. We identify about 500 “target” catchments where recent (i.e., after 1999) megafloods have occurred that are surprising based on local data. We perform a hindcast experiment of predicting their peak discharge with regional envelope curves, using flood observations from similar “donor” catchments up to the year before their occurrence. From this group of donor catchments we construct an envelope curve which we compare with the megaflood that occurred later in the target catchments. We repeat this analysis for all the detected megafloods in the target catchments.

Our analysis shows that, in 95.5% of the target catchments, the discharge of the envelope is larger than that of the observed megaflood, suggesting that, from a European perspective, almost none of the events can be considered a regional surprise. Similar results are obtained by repeating the analysis on two consecutive sub-periods, indicating that megafloods have not changed much in time relative to their spatial variability. In conclusion, our findings show that recent megafloods could have been anticipated from observations in other parts of Europe, which would not be possible using only national data.

Team members:

Milon Bohac, Marco Borga, Attilio Castellarin, Giovanni Battista Chirico, Pierluigi Claps, Eleonora Dallan, Irina Danilovich, Daniele Ganora, Liudmyla Gorbachova, Ondrej Ledvinka, Maria Mavrova-Guirguinova, Alberto Montanari, Valeriya Ovcharuk, Alberto Viglione, Elena Volpi, Berit Arheimer, Giuseppe Tito Aronica, Ognjen Bonacci, Ivan Čanjevac, Andras Csik, Natalia Frolova, Boglarka Gnandt, Zoltan Gribovszki, Ali Gül, Knut Günther, Björn Guse, Jamie Hannaford, Shaun Harrigan, Maria Kireeva, Silvia Kohnová, Jürgen Komma, Jurate Kriauciuniene, Brian Kronvang, Deborah Lawrence, Stefan Lüdtke, Luis Mediero, Bruno Merz, Peter Molnar, Conor Murphy, Dijana Oskoruš, Marzena Osuch, Juraj Parajka, Laurent Pfister, Ivan Radevski, Eric Sauquet, Kai Schröter, Mojca Šraj, Jan Szolgay, Stephen Turner, Peter Valent, Noora Veijalainen, Philip Ward, Patrick Willems, Nenad Zivkovic

How to cite: Bertola, M. and Blöschl, G. and the Team members: Surprising megafloods in Europe – learning from the big picture, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5997,, 2024.