Elio Biadici in front of his house in Piano di Peccia, in the Maggia Valley in southern Switzerland, on July, 3, 2024. Heavy thunderstorms triggered devastating debris flows and damage in the region in late June 2024.
Keystone / Michael Buholzer
High in the mountains, a sudden downpour can turn a quiet slope or valley into a roaring river of mud and rock within minutes. And these intense downpours are predicted to become more frequent. The man in charge of a new Swiss research institute on mountain hazards spoke to Swissinfo about how the climate crisis is reshaping risks in the Alps.
This content was published on
August 27, 2026 – 09:00
Markus Stoffel holds the newly-created Chair of Mountain Hazard Research at the University of Geneva. He and other scientists warnExternal link that climate change is rapidly escalating disaster risks in the Alps. Melting glaciers, shrinking snow cover and thawing permafrost are destabilising mountains, triggering more rockfalls, debris flows and cascading hazards that threaten communities and infrastructure.
Professor Markus Stoffel is the head of the University of Geneva’s new Chair for Mountain Hazard Research.
UNIGE
At the same time, precipitation patterns are shifting. Swiss summers are expected to become drier, but heavy rainfall will intensify across all seasons. Short, intense downpours are projected to grow both more frequent and up to 30% strongerExternal link, with rain falling in increasingly concentrated bursts.
“That water can erode more material,” StoffelExternal link told Swissinfo. “So there is a possibility that debris flow catchments will produce events without historical precedents.”
Stoffel leads a research team working to better understand how climate change is reshaping debris flows and other Alpine hazards – and how risks can be reduced. In collaboration with public and private partners, the project aims to develop strategies to limit future losses and damage.
The six specialists are studying how warming, shifting precipitation, glacier retreat and permafrost thaw affect the frequency, scale and impacts of hazards in mountain regions, including debris flows, avalanches, rockfall, and large-scale slope movements. Launched on May 1, the five-year project is backed by €1 million (CHF920,000) from the AXA Fund for Human Progress.
“The rock-ice avalanche in Blatten last year or the fatal debris flows in summer 2024 underscore the pressing need to improve understanding of these processes and their dynamics. While we won’t be able to avoid the occurrence of these phenomena in the future, we can certainly mitigate the resulting damage,” said Stoffel.
Unprecedented debris flows
Like other Alpine hazards, debris flows can be deadly and extremely costlyExternal link. In summer 2024, violent storms caused destructive debris flows across the Alps, striking southern Switzerland (Val Bavona, Valle Maggia), northern Italy (Valle d’Aosta and Piedmont), as well as parts of Austria and Germany.
The frequency and severity of debris flows is bound to increase as glaciers retreat and permafrost thaws, loosening sediment on mountainsides. The volume of Swiss glaciers has reduced by almost 40%External link since the year 2000, and the glaciers continue to lose mass each year.
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Stoffel reckons that over the course of the 21st century the lower boundary of permafrost is likely to shift upwards by 200 to 750 metres, depending on exposure of the slopes, ground composition and ice thickness. This will lay bare new sediment sources and increase the likelihood of larger debris flows, said the professor.
>>Read more about the impact of the warming planet on permafrost.
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‘Destruction potential could be higher’
Debris flows occurred in the past, but not as often and typically in summer. Now the season is extending.
“We’ve already had events occurring earlier – so May, sometimes even April – and extending later into October,” said Stoffel.
They can even occur in winter. Stoffel highlighted the case of January 2018, when the Swiss Alps saw heavy snowfalls, followed by warm temperatures, more heavy rain and snow.
“We had huge avalanches coming down in different parts of the Alps and then suddenly debris flows in the middle of winter. Something that we hadn’t experienced before. This was maybe a glimpse of what we could expect by the end of the century,” he said.
While Swiss hazard zones are well-mapped and the regions affected by debris flows and flash floods are generally known, higher rainfall volumes mean debris flows may travel further and with greater force.
“With larger precipitation volumes the energies of debris flows [and the destruction potential] could be higher,” Stoffel said.
>>Small landslides are on the rise in the Alps due to climate change, but it’s less obvious what is causing large-scale natural disasters. Read more about this below.
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Climate change – only part of story
One important caveat, however, is that sediment is not unlimited. A massive debris flow can completely flush a catchment down to its bedrock, Stoffel says. When this happens, the system needs time to “refill” via rockfalls from higher on the mountain before another debris flow can occur, meaning some areas might temporarily become safer even if intense storms continue.
“This is what makes it really difficult to make general statements of what will happen and what will change,” said the professor.
He also insists that climate change is only part of the story behind mountain hazards.
“We estimate the influence of climate change to be one-third to 50%. The other two-thirds, or 50% of the risk, was really the result of more infrastructure over time…it’s also the result of human decisions, mostly decisions that were taken in the past,” he said.
This is reflected in the transformation of the Alps in the second half of the 20th century, when mountain settlements expanded and became more densely populated. Before 1950, villages were largely isolated, but the postwar boom brought roads, bus networks and ski lifts that reshaped settlement patterns. Population growth – over 30% between 1950 and 1970 – along with a surge in tourism and second homes, drove expansion in accessible Alpine regions.
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Part of wider scientific network
Stoffel’s Geneva-based team joins a strong network of scientists studying mountain hazards in Switzerland, such as the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), the federal technology institutes ETH Zurich and EPFL, and the universities of Lausanne, Zurich and Fribourg.
But he says his team will take a slightly different approach. While places like ETH Zurich and WSL do deep, high-tech case studies at specific sites (like the Illgraben debris catchment in canton Valais), Stoffel’s department’s work will focus on the big picture. They intend to build massive archival databases to look at regional tendencies, tipping points and cross-Alpine trends to see if changes in one region such as the Swiss Alps mirror what happened decades ago elsewhere – the southern French Alps, for example.
Building on two decades of research, the scientists will also combine field observations, remote sensing and process modelling to better understand when and where slopes fail, how far destructive flows can travel, and what this means for exposed communities and critical infrastructure.
Against this backdrop of growing risks and uncertainty, Stoffel stresses the need for flexibility: while some mountain regions will face more frequent hazards, others may stabilise.
“We may face crises and have situations that become worse but elsewhere the situation may improve – or remain largely unchanged for decades,” he said.
>>The Blatten disaster resulted in an unprecedented scientific effort to understand what happened and why. Read more here:
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Edited by Gabe Bullard/Veronica De Vore
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