PSILOGO

Laboratory for Particle Physics (LTP)

LTP Colloquium

The Dynamics of Snow Avalanches

Thursday, June 21, 2007, 16:00
WHGA Auditorium

P. Bartelt, WSL, Swiss Federal Institute for Snow and Avalanche Research, SLF, Davos, Switzerland

Abstract:
This talk will provide an overview of the mechanics of snow avalanches and other dangerous gravitationally driven rapid mass movements. After a brief presentation of the WSL and the activities of the research unit "Snow Avalanches, Debris Flows and Rockfalls", the following questions will be addressed:

  1. How well can engineers and land planners predict the runout distances and impact pressures of snow avalanches? Some case studies from the avalanche winter of 1999 will be critically discussed.
  2. How do we investigate full-scale flows? Results (including videos) from our experimental site in Kanton Wallis will be presented. Definition of some important terminology.
  3. What are the energetics of avalanches? How energy "efficient" are avalanches at converting the available potential energy into kinetic energy? Why can an avalanche destroy a mountain forest so easily?
  4. What is the role of random kinetic energy in avalanche motion? Derivation of fluctuation-dissipation relations for snow avalanches. How do granular fluctuations interact with frictional mechanisms?
  5. What is the nature of "steady-state" in a finite sized surge? How do avalanches stop and how can small harmless avalanches grow into potentially dangerous flows? Presentation of laboratory experiments showing the internal structure (front, bulk and tail) and comparison of frictional work rates with gravitational work rates.
  6. Are avalanches self-organizing? If avalanches can reach a steady state, then basal shearing and internal viscous shearing compete, minimizing entropy production. That is, can avalanches self-organize the frictional mechanisms to reach an "optimal" state of least wasted gravitational work?
  7. How do we model snow avalanches? We provide avalanche practitioners with state-of-the-art numerical models to predict runout distances and impact pressures. Geographic information systems and hazard mapping.