Dry snow avalanches consist of two distinct layers. A dense-flow layer is superposed by a powder-snow layer, a cloud of relatively small ice particles suspended in air. The density of this suspension is one order of magnitude smaller than that of the dense flow. A simulation model for dry avalanches has been developed, based on separate sub-models for the two layers. The sub-models are coupled by an additional transition model, describing the exchange of mass and momentum between the layers. The fundamentals of the two-dimensional granular flow model for the dense flow and of the three-dimensional turbulent mixture model for the powder flow are presented. Results of the complete coupled model, SAMOS (Snow Avalanche MOdelling and Simulation), applied to observed catastrophic avalanche events, are discussed, and the prediction of powder-snow pressures acting on a tunnel bridge is briefly described. SAMOS is used routinely for hazard zoning at the Austrian Federal Service for Torrent and Avalanche Control.

A huge avalanche could be released artificially, which permitted extensive investigations (dynamic measurements, improvement of measurement systems, simulation model verification, design of protective measures, etc.). The results of the velocity measurements from the dual frequency pulsed Doppler avalanche radar of the AIATR and the recalculation with the numerical simulation model SAMOS are explained in this paper.

Two-or three-dimensional avalanche-simulation models offer a wide range of applications; however, a challenging model-verification process is demanded, accompanied by a reliable determination of model-input parameters. We show that a verification process can be arranged with remotemonitoring data from an artificially triggered avalanche, leading to the calculation of avalanche mass balance. Two numerical methods are applied to increase the quality of the parameter fit and to reduce the number of simulations. The quality of the parameter fit is verified by comparing measured and simulated run-out lengths. In addition, a cross-check is performed using velocities derived from Doppler radar measurements.

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