The scale effect in extreme snow avalanche runout distance

Abstract

The scale effect in avalanche runout distance refers to the question of whether paths with larger scale such as total vertical drop may have longer runout distance than shorter paths. Here the effect is analyzed using 475 values of extreme runout distance measured from five mountain ranges. The results show that within each range there is such a scale effect. However, the statistical significance of the scale effect reduces sharply as the median scale parameter, such as total vertical drop, increases. Results from maximum speed data of avalanches also show that maximum speed increases with path scale. The reduction of significance of the scale effect with the path scale combined with the speed data analysis suggests that the terrain just upslope of the runout zone may be crucial in determining the runout distance. The overall results should be of interest to those attempting to model avalanche runout using either empirical statistical methods or avalanche dynamics.