The volume of the landslide in the Engadine that thundered into Val Roseg on Sunday morning is estimated at over one million cubic meters. This makes it comparable to the landslide in Bondo in 2017. Even if the most recent landslide may have had a mild outcome, the question arises as to what we can learn from such landslides. Flavio Anselmetti, professor and geologist at the University of Bern, knows more.
Flavio Anselmetti
geologist
SRF News: How are we prepared for such dangers?
Flavio Anselmetti: Normally you do monitoring by using laser measurements or sensors in the wall to see whether it is moving. Then you get early warning signs if an event is imminent. During intense rain, for example, you notice an acceleration of movements. There is a warning time that tells us when the mountain could come.
How does the population know where there is a risk?
In general, you have to walk through the mountains with a watchful eye and pay attention to the signs. Rockfalls often indicate that something bigger could be coming. Otherwise, there are hazard maps that are publicly available on the Internet. In principle, landslides can occur in all mountain regions.
You have to walk through the mountains with a watchful eye and pay attention to the signs.
But a hotspot, for example, is Kandersteg in the Bernese Oberland, where the sharp stone has moved. A whole mountain side is now moving there. Brienz is also affected or the mountains along the Gotthard line. However, through monitoring you can observe and predict movements very well.
To what extent does climate change cause such events?
Climate change certainly plays a role, but it must also be said that all of these mass movements also take place without climate change. There have always been landslides and debris flows in the Alps. But: With increasing climate change, nature is becoming unbalanced.
There have always been landslides and debris flows in the Alps.
For example, the permafrost is thawing at over 2500 meters: It may be that the warming there leads to new adjustments in the mountain masses. Extreme precipitation could increase in the future, which in turn has a destabilizing effect. But it is not yet clear how frequently such events will occur in the future.
What are the risks outside of permafrost?
Basically, you have to look at the basic disposition: How receptive is a mountain side to mass movements? This depends on the type of rock, the stratification, the fissures and the hydrology. Basic disposition tells us how frequently or easily an event could occur.
Then we need a trigger: an earthquake or extreme rainfall. Melting permafrost would be a basic condition that can occur above 2500 meters. This means a latent increase in the risk of landslides at these altitudes, which does not exist in lower areas.
Legend:
Over a million cubic meters of rubble came loose from the rock on Sunday morning.
KEYSTONE/Gian Ehrenzeller
What lessons can be learned from the landslide in the Engadine?
This event is certainly a nice example. It has been warm the last few days, but we are at an altitude that is actually in stable permafrost, at 3500 meters. You now have to look closely at what triggered this mountain surge and why the mountain gave way. The findings will then help to redo the entire risk assessment in Val Roseg or a similar valley.
The interview was conducted by Can Külahcigil.
