Computational models for dense snow avalanche motion
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- NGI report 
Seventeen various models of dense snow avalanche motion are presented. These include statistical, comparative and energy considering models for runout distance computations as well as dynamic models for avalanche motion simulations. The latter describe either the internal dynamics of the material at certain stages of the motion, the dynamics of the moving mass as a whole from initiation to rest, or combinations of these. The dynamic models are presented with regard to the physical description of the moving material and to the mathematical and numerical modelling. Most of the dynamic models are rooted in hydraulic theory where the moving masses are described as a fluid, but also granular flow models inheriting geotechnical aspects of soil mechanics are included. Simple (quasi) three-dimensional models exist, but most of the models are still of one and two dimensions. Rather than expanding more existing models into three dimensions, the author suggests to improve the one- and two-dimensional dynamic models further, preferably by combining models based on Bagnold's (1954) concept of dispersive pressure and dynamic shear with granular flow models involving aspects of soil mechanics. Density variations, nonhomogeneous concentration, particle size distribution, cohesion, particle rotation as well as temperature changes and energy dissipation are not adequately described in any of the dynamic models. Furthermore there is a conspicuous lack of any description of stability and accuracy of the applied numerical methods. Examples of travel distance computations based on one statistical, one comparative and three dynamic models are finally presented for four Norwegian avalanches.