The village of Blaten striped from the map, localities in danger, cut roads and isolated inhabitants at the bottom of the valley … Recent news highlights the natural dangers faced by Switzerland. This mountain country was not spared by avalanches, landslides and floods during its history. But as early as 1998, climatologists feared an upsurge in these risks.
Switzerland saw one of its deadliest natural disasters in 1806 during the Goldau landslide which kills 457 people and 323 animals. The show History calendar Recall this drama:
During 19e Century, water correction works, the construction of flood protection dikes and the establishment of works to ward off the avalanche triggers are undertaken on a large scale. However, from 1875, the Swiss lived for a century a period of lull and were less concerned with natural dangers.
Damage of a rotten summer
But in the summer of 1987, serious bad weather broke the feeling of security that the Helvetians were rocked. Following heavy rains, the alpine arc is the victim of floods, landslides and torrential lavas. The cantons of Graubünden, Uri, Ticino and Valais undergo significant floods. Eight people lose their lives. The damage is encrypted at 1.3 billion francs.
In Valais, the most affected village is that of Münster in the Conches valley, as shown in this extract from the program Present time, “Chronicle of a rotten summer “, broadcast in 1988.
Le PNR 31
Following these events, prevention of natural risks is more taken into account. And in the process, 20 million francs will be allocated to a national research program, the PNR 31 entitled “Climate change and natural disasters”. Scientists then seek to establish if the climate really changes and what could be the consequences in Switzerland of an increase in temperatures. In 1998, they published their results. In his program entitled: “global warming, scenarios for Switzerland”, Telescope Open the file with a first observation.
All models give us accelerated warming from the planet
PNR 31 lists the potential consequences of global warming. The rise in temperatures is likely to cause in particular the melting of glaciers, thaw of permafrost and more precipitation. In French -speaking Switzerland, the mountainous canton of Valais is particularly exposed to these consequences.
The threat of glaciers
Sensitive witnesses of climate change, the glaciers melt and lose their mass with sometimes dramatic consequences in the event of an collapse or in the event of the formation of the glacial lake.
We remember the Mattmark tragedy caused in 1965 by the collapse of a pan of the Allalin glacier on the dam site.
In 1968, the rupture of a glacial lake inflated the waters of the Torrent Felsbach which carried around 400,000 m³ of materials from the Moraine du Grubengletscher in the village of Saas Balen.
The Dégel du Pergélisol
Pergélisol or Permafrost, a layer of the frozen floor all year round, cements the land in the mountains and ensures the stability of the geological layers. His thaw caused by the rise in temperatures is likely to cause rock falls or torrential lavas.
The state of the Permafrost is the subject of geological monitoring sustained in several regions of Valais in 2001.
A melting of permafrost, intense precipitation and cascading consequences: a torrential lava takes everything in its path and forms a dam on the Drense creating a pocket of water threatening the city of Martigny below which must be evacuated in the middle of the night. With the cantonal geologist Valaisan Jean-Daniel Rouiller, return for Time On this July 25, 2006 in Bovernier in Valais.
Torrential lava is not a new phenomenon, a glacier that melts, at least at times, it is nothing new. What is new is the resurgence (…) of these phenomena
Abundant precipitation
High temperatures can cause more thunderstorms and strong precipitation. The brutal and dramatic consequences of torrential rains strike the spirits: the sudden flood as in Brig where the furious waters of Boueuse surge in 1993 or even in October 2020 the Gondo disaster and all the Valais affected following torrential precipitation. At the time of the balance sheet, the cantonal geologist Valaisan Jean-Daniel Rouiller brings his expertise once again.
Intense or repeated rains cause water infiltration in the soil, likely to cause landslides.
On July 19, 1994, the Falli-Hölli holiday hamlet in the heights of Plasselb in the canton of Friborg was striped from the map by a gigantic and inevitable landslide. This movement on the ground had accelerated under the eye of the experts.
Risk areas
Faced with the dangers, reinforced by climate change forecasts, the Federal Planning Office of Planning Recommended in 1997 the creation of risk areas in all Swiss municipalities. But that is not without difficulties. Once again Jean-Daniel Rouiller, cantonal geologist Valaisan, is the privileged interlocutor of RTS.
Detecting dangers does not yet mean preventing them … The canton of Valais, particularly subject to climatic hazards, undertakes infrastructure security work. In 2016, nearly 300 projects were pending.
Live under threat
Many Swiss are installed in threatened regions and choose to stay there, sometimes at a certain peace of mind.
I know there is no future here.
In 2013, in the program Time Entitled “Debacle in the Alps”, Albert von Bergen who lives in Flesch in a risk area, confides in journalist Raphaël Engel.
Marielle Rezzonico for the RTS archives