Experimental devices to determine snow avalanche basal friction and velocity profiles

Physical modelling is an important tool for obtaining insight into the internal flow structure of gravity currents such as snow avalanches, or, more practically, for estimating the dimensions of avalanche defense structures. We present a large-scale experimental setup, which allows the generation of avalanche-like gravity currents of snow under reproducible experimental conditions. The Weissfluhjoch chute is 34 m long, 2.5 m wide and can be run with up to 25 m3 of natural snow. We present two types of optical velocity measurement devices based on the correlation method. We discuss their applicability to snow flows and perform an error analysis of the observed flow velocities. Furthermore, preliminary results of velocity profile measurements in the snow flow are presented. We also describe the experimental determination of the total dynamic basal friction force exerted on the ground. An effective dynamic friction coefficient is calculated.