Über die Wirksamkeit der Stützverbauung von Lawinen : Schutz des Lebensraumes vor Hochwasser, Muren und Lawinen : INTERPRAEVENT

On the effectiveness of avalanche control by supporting structures

1988

45 Lit. Ang.

Unselbständiges Werk

13124

200076254

Avalanche control in the starting zone of avalanches by means of supporting structures has started 120 years ago in the Swiss Alps. This contribution give a condensed historic account of the development of that control technique. During 40 winters the SFISAR has studied, in several defense areas, the interactions of the supporting structures with the snowpack and special attention was given to critical avalanche cicles when an instable new snow layer provoked avalanching among the structures. Here, the results of those observations are presented. The interactions between moving snow and supporting structures were also studied on the test glide near the institute. The experiments allowed the measuring of impact forces and the mass of snow that moves accross the grates of different types of structures. With the aid of the results gathered from the test glide experiments an attempt is made to calculate an avalanche starting in a given avalanche path with and without avalanche control by supporting structures. As the winter observations showed, the starting of a new snow direct action avalanche cannot be controlled entirely by supporting structures. Once a soft slab has started among the structures it will be slowed down by the structures but most of the snow will flow through the grates thus forming a medium size avalanche in the track below the starting zone. Supporting structures will entirely hold in place the settled old snowpack and prevent in most cases the fracture of a direct action avalanche. But the starting of a new snow avalanche cannot be prevented in all cases. This must be kept in mind when avalanche hazard maps have to be prepared in places lying below an avalanche starting zone controlled by supporting structures.