The mass balance of flowing avalanches

In practical avalanche dynamics calculations, the entrainment of the snow cover and the mass deposition along the avalanche path are not considered. Numerical avalanche dynamics models assume that the mass of the avalanche is constant along the track, under the assumption that the snow mass that starts from the release area is the same mass that arrives in the deposition zone.

Observations show, however, that these assumptions are clearly false. Part of the snow cover will usually be eroded, sometimes down to the ground, and at the same time, local or continuous deposits will be distributed along the path. Because the mass balance of avalanches is not modelled correctly the validity of our present generation of avalanche dynamics models is called into question. In this project both field and laboratory experiments will be used to investigate mass entrainment and deposition processes in flowing avalanches. Our goal is to develop laws that realistically simulate mass changes in numerical models.

Erosion and deposition processes at the Vallée de la Sionne test site.

In order to reach this goal we plan to use high resolution photogrammetric measurements at the Swiss Vallée the la Sionne test site along with existing field measurements at the Italian Mount Pizzac test site. Furthermore, in order to develop entrainment and deposition laws for numerical models, granular experiments in a laboratory chute will be performed, where velocity profiles and mass changes can be exactly measured. In summary this work will involve:

1. defining the measurement techniques and devices to capture mass changes in flowing avalanches,
   
2. performing entrainment and deposition tests,
   
3. analysing the test results,
   
4. developing a theory of mass entrainment and deposition from the experiments and field observations,
   
5. developing numerical models and practical calculation methods to treat mass entrainment and deposition,
   
6. and finally documenting and publishing the results.

Contact

• Betty Sovilla