the great fear in the mountains

At the end of last week, the Oisans and Écrins valleys were hit by floods and torrential lava with catastrophic consequences. After the amazement at the images of the mythical hamlet of La Bérarde devastated, now comes the time for questions, numerous and dizzying.

La Bérarde seen from the air, Friday June 21. © Civil Security

La Bérarde, heart beaten from Oisans

Footbridges washed away, roads damaged, campsites and shelters evacuated, hamlets and villages flooded, cut off from the world or even devastated… In the Vénéon valley, but also in Vallouise, Valbonnais, Valgaudemar, Champsaur or Guisane… everywhere in the Écrins, the swollen torrents have caused great damage, placing these mountain areas in a situation of emergency and distress.

According to Pierrick Navizet, from the Écrins National Park, “ the entire park was affected and in particular the Haut-Vénéon sector which was critical “. In Oisans, the Étançons torrent has swelled to such an extent that the Bérarde is unrecognizable, the ancestral buildings of the hamlet having been swept away by the waters and everything they carried with them.

Thanks to the work of the helicopter rescue services, no casualties have been reported, despite sometimes desperate situations. Fortunately, all residents and tourists present in the affected valleys were able to be rescued from the disaster in time and taken care of. But it is an understatement to say that the emotion is strong among lovers of this Mecca of mountaineering in France. A prize pool was also initiated in solidarity with the residents of Saint-Christophe-en-Oisans, raising more than €30,000 in three days.

Accelerated crisis

Now that residents are safe and the roads are closed, it is time to take stock of the damage and decipher the phenomenon. The combination of torrential precipitation (the cumulative rainfall recorded over 24 hours exceeded 100 mm in places) and snowmelt (while the thickness of the mantle is very significant this season) partly explains the exceptional nature of the episode. But according to forecaster Gaétan Heymes, “ [ce] is probably not enough to explain on its own the scale of the disaster “.

To believe in an isolated event is to forget that the valleys of Oisans and Ecrins affected by floods and torrential lava in recent days unfortunately have a recent history in terms of meteorological events with destructive consequences. Last summer, a ten-year flood had already weakened Oisans. The damaged Châtelleret refuge has been closed since. In the valley, this is the second building with an uncertain future after the definitive closure of La Pilatte, a victim of climate change. “ It’s like a wound that hasn’t yet healed
», translates Symon Welfringer, forecaster at Météo-France and mountaineer. Especially since the flood episode that we have just experienced is more of the order of every 20 years, or once every 20 years.

The destabilization of glacial moraines by rapid global warming and the stock of materials mobilized by the torrential lava at the end of July 2023 in the Étançons valley is an avenue to explore “, estimates Gaétan Heymes, while his geomorphologist colleague Mélaine Le Roy speaks of a sedimentary crisis coupled with a hydrological crisis.

Geophysicist specializing in natural risks, Éric Larose maintains that “ we have probably entered a period of erosive crisis ” with a ” increase in frequency and intensity of sediment transport of all sizes from upstream to downstream » and the consequences of global warming which “ gradually affect the middle mountains and the valleys
», beyond the disappearance of glaciers and permafrost in high mountains. The hypothesis of a glacial pocket rupture in the Bonnepierre valley is also being studied.

The reconstruction in question

Questioned by the Dauphiné Libéréthe mayor of Vallouise-Pelvoux indicates that “ work related to the damage caused by storm Aline last fall was completed a month ago. Only one month. And now we have to start all over again. Redo everything. We need help from the state. If we do not have the administrative authorizations to dig the torrents, to build real protection against rising waters, then we will no longer be able to guarantee the safety of our inhabitants.. » In Saint-Christophe-en-Oisans, a state of natural disaster will be requested.

The episode is reminiscent of that of October 2020, in the southern Alps. Storm Alex wreaked havoc in four valleys in the Nice hinterland: Vésubie, Roya, Tinée and Estéron, with a human toll of 10 dead, 8 missing and more than 10,000 victims. In Saint-Martin-de-Vésubie alone, 90 houses were swept away, as well as public buildings, roads and several bridges in the valley. “ Natural risks have always been an integral part of life in the mountains… Their recurrence and the increase in their effects, consequences of global warming, strongly question the “liveability” of our valleys… », asks Vincent Neirinck, from Mountain Wilderness.

If financial aid to communities is expected, the debate is underway on the choice of rebuilding everything or not. In the upper Vénéon, voices are already being raised to demand reconstruction, such as those of Marie-Claude Turc, manager of La Cordée in Saint-Christophe-en-Oisans or Sandrine Delorme, guardian of the Promontoire refuge – fortunately spared this time. Researcher Philippe Bourdeau calls for questioning the merits of identical reconstruction and adapting to the new climate order.

Bad weather also in Savoie and Switzerland

In Switzerland too, bad weather has caused damage. One person was found dead while two others are still being sought in the Mesolcina valley after the violent weather which affected the canton of Graubünden. In Valais, the village of Zermatt was cut off from the world, while 230 people had to be evacuated from the canton.

In Tignes, in Savoie, the summer season was postponed following the overflow of the lake and the flooding of the technical premises of the ski lift company. In Maurienne, the Arc was also in flood. Finally, in the Mont-Blanc massif, the Leschaux refuge closed its doors temporarily following landslides leading to rock falls on the refuge terrace, a consequence of the large quantities of snow and water upstream. .

At Madame Carle’s meadow, repeated floods. © T. Maillet / Écrins National Park


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