The complex parameters and physical variables responsible for the onset and behavior of an avalanche were considered by an international team of researchers in developing a highly accurate digital simulation of a snow slab avalanche.
Acknowledging that snow in this type of avalanche behaves as both a solid and a fluid, researchers from the U.S. and Switzerland devised the first realistic, complete and scientifically rigorous simulation of a snow slab avalanche, which occurs when a very clear linear crack appears at the top of the snowpack. This usually happens when, over a large area, there is a weak and not very cohesive snowpack layer under the dense top layer of snow, known as the slab.
A snow slab avalanche is usually triggered when there is an extra load – such as a crossing skier – on the snow, or when the snowpack is destabilized in some other way. A crack appears in the bottom layer of snow, which can spread rapidly. The snow is now behaving in accordance with the principles of solid mechanics. As the crack spreads, the weak layer's porous structure causes it to collapse under the weight of the surface slab. The slab is then released and begins to slide across the weaker layer. The collisions, frictions and fractures that the solid snow experiences as the top layer slides downward and breaks apart lead to a collective behavior characteristic of a fluid.
The collapse of the porous bottom layer was successfully simulated for the first time at a large scale using a continuum approach. The model integrates only the relatively few key parameters that dictate how the snow will behave at the various stages of the process, such as the dynamics of the fracture, friction and the level of compaction based on the type of snow.
The findings, which are published in Nature Communications, could be used to enhance risk management in alpine areas. Scientists from Swiss Federal Institute of Technology, WSL Institute for Snow and Avalanche Research SLF, University of California-Los Angeles and University of Pennsylvania contributed to this study.