Can the effects of megafloods in Europe be anticipated?

On September 3, an isolated depression at high levels put almost the entire Spain. In some points, up to 172 liters per square meter accumulated and the floods of some rivers They left several dead.

A month later, Storm Aline shattered all records: in the capital of Madrid it had not rained so much for more than 130 years, according to the records of the State Meteorological Agency (Aemet).

“Fortunately, these types of extreme events or megafloods occur very occasionally, but they can happen anywhere”and that makes them “very difficult to predict”Luis Mediero, professor at the Polytechnic University of Madrid, explains to EFE.

And this difficulty in predicting them means that cities are poorly prepared and response measures are insufficient, which aggravates their catastrophic impacts and causes loss of life, comments the engineer.

However, according to a study published in Nature Geoscience, the effects of megafloods in Europe can be estimated from observations of previous floods, information that would help implement the necessary measures to defend the population from these events.

“Until now, these types of studies had not been done because a very extensive database is needed from a sufficiently large area, in which a few floods of this type have taken place”says Mediero, co-author of the Nature Geoscience article.

The study, led by Miriam Bertola, from the University of Vienna (Austria), has analyzed river flow data recorded at 8,000 points across Europe between 1810 and 2021, and has identified 510 megafloods.

Some of them took place in Spain, such as the one in the Almanzora River (Almería) in 1973, a flood that left ten dead in the area, or the one that affected the town of Orihuela (Valencia) in 2019, which left almost 500 liters accumulated. and caused the Segura River to flood.

Outside of Spain, the article mentions some of the most notable events recorded in central Europe, such as the flooding of the Rhine in Germany in July 2021, caused by heavy rains in the west of the country, in some areas of Belgium and in the Netherlands. and Luxembourg and that left more than 200 dead and million-dollar losses.

The article explains that regions with similar hydrological characteristics tend to produce very similar extremes throughout the continent and that the 95.5% of the observed megafloods could have been predicted “based on previous events in similar locations.”

According to the authors, the study of these megafloods could provide an indication of the magnitude of the floods that could be expected in other places in Europe with similar characteristics, and that information “It would help the emergency services to be aware that something like this can happen, and to explain to citizens what they have to do, and to implement the necessary preparation measures to reduce the damage of these floods,” point.

The study highlights and demonstrates that it is important “go beyond local watersheds” when evaluating the risk of flooding and taking into account the phenomena of other places and basins.