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Dieter Issler

Experiments on Snow Avalanches and Their Implications for Modelling

Abstract: Field observations and dedicated experiments on snow avalanche flow have been carried out in several countries over the past 60 years. Both full-size tests in instrumented avalanche tracks and laboratory experiments with snow or substitute materials are used here to extract information on two major questions: (i) Which flow regimes are possible in avalanches and under which conditions do they occur? (ii) By which mechanisms and at which rate do avalanches entrain snow from the snow cover? The major types of sensors used in avalanche experiments are briefly discussed, and it is seen that a large variety of sensors and experimental techniques---including laboratory experiments---have to be combined in order to obtain definitive answers to the open questions. It appears that the models presently used in engineering practice and land-use planning are too simple to capture the wide variety of behaviour observed in dry-snow avalanches. One of the practically most cumbersome indications of this failure is the wide range of the friction parameters obtained from back-calculations of observed avalanche events. The potential of new models as well as extensions of existing models to describe flow-regime transitions and dynamically determined snow entrainment is examined.