Two million avalanches in Grisons

02.06.2023  |  Jochen Bettzieche  |  News SLF

SLF researchers are simulating avalanches to create hazard indication maps that also cover previously unmapped areas. This is particularly useful in assessing hazards for projects outside building zones and for making local people aware of these dangers.

Up to 84% of the surface area of the canton of Grisons is at risk from avalanches – around four out of every five square metres. Much of this is currently protected by forest, but even so, two thirds remains potentially at risk. That equates to over 4,700 square kilometres, almost nine times the size of Lake Constance. These are the findings of researchers at the WSL Institute for Snow and Avalanche Research (SLF), in cooperation with the canton's Office for Forest and Natural Hazards (AWN).

To obtain the results, the scientists – commissioned by the Canton of Grisons – modelled scenarios with and without forests for return periods of 10, 30, 100 and 300 years. "In total, we've simulated 2 million avalanches for the canton," says Yves Bühler, Head of the SLF's Alpine Remote Sensing research group.

This has resulted in large-scale avalanche hazard indication maps for the entire canton. While detailed hazard maps were already available previously, they only covered settlement areas, explains the AWN's natural hazards expert Roderick Kühne. The new maps provide important information for projects outside building zones. These include mountain huts and hunting lodges as well as infrastructure such as ski facilities. "The results also offer an overview of the risks to roads and railway lines," adds Bühler. In addition, the protective effect of forest can be better quantified by comparing the scenarios with and without forests. The maps are not only a useful tool for experts, but also allow policymakers and local people to visualise potential avalanche risks.

Bühler and his team used the SLF's Rapid Mass Movement Simulation (RAMMS) software for their work. RAMMS enabled them to combine the automatically identified starting zones for avalanches with a numerical simulation of the runout distances. This required intensive discussions with experts from the field. It has taken 10 years of development to reach this point, but the time-consuming work has been worthwhile. A comparison with existing hazard maps has shown that the results usually match up surprisingly well. "Such maps can be calculated for all regions for which spatially high-resolution terrain models and information on snow climatology and the protective effect of forest are available, even where there is currently no information available on the danger from avalanches," says Bühler with conviction.

This means that there is plenty of demand for the new approach. The SLF team has already simulated avalanches for the canton of Valais. The researchers have just completed that project and have embarked on another for the canton of Ticino. "The Federal Office for the Environment has also expressed an interest," says Bühler. His work is proving very popular abroad too, with orders received from Italy, Alaska, New Zealand, Georgia and Afghanistan. And it doesn't stop there, concludes the researcher: "We're currently planning further applications, for example in Uzbekistan."


Roderick Kühne

Projektleiter Naturgefahren

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