Full-scale avalanche experiment

A successful full-scale avalanche experiment took place today at the Vallée de la Sionne avalanche test site in Valais (Arbaz district). An international research team of the WSL Institute for Snow and Avalanche Research SLF is expecting the experiment to enhance their understanding of how large avalanches dynamics, of the forces they generate, and how communities, transportation routes and infrastructure can best be protected.

At the SLF test site, which is without parallel worldwide, explosives fired from a helicopter triggered a powder avalanche - the largest avalanche in this test area in 11 years. The avalanche has travelled a distance of around 2.5 km down to the valley bottom. It also struck the 20 m mast situated in the avalanche path, to which numerous measuring instruments are attached. Among the other resources used by the researchers to measure the movement of the avalanche and the resulting deposits accurately were laser scanners, and thermal imaging cameras.

The research team were delighted with the successful outcome. "For this experiment to succeed, several parameters have to be favourably aligned, including the snow quantity, bonding of the snowpack, and good visibility for the helicopter flight and measuring instruments," explains Betty Sovilla, the scientific director of the trial. For this reason, such experiments can be performed only on rare occasions. In the 20 years since the test site was established, 12 full-scale measuring campaigns have taken place in Vallée de la Sionne. In addition, measurements are recorded during around 20 naturally triggered avalanche events a year. The researchers use the findings for multiple purposes, including to refine the RAMMS computer program, which simulates large avalanches. In turn, the program helps natural hazards experts to calculate avalanche runout distances and the appropriate dimensions for avalanche defences.