Magnitude and Frequency of Avalanches in Relation to Terrain and Forest Cover

Abstract

This paper contains an analysis of magnitude and frequency of avalanches in relation to terrain and forest cover variables. The analysis was applied to 194 avalanche paths in four avalanche areas along highways in British Columbia with approximately 25,000 avalanches recorded. The magnitude and frequency for the avalanche paths were estimated from data collected along the highways by avalanche technicians. Results show that mean magnitude and mean frequency are weakly correlated for a set of avalanche paths in an avalanche area. In addition, with magnitude and frequency viewed as response variables, magnitude and frequency correlate with different sets of predictor variables from one area to another. This paper contains the first comparison of variables which correlate with magnitude and frequency from one avalanche area to another. The results show that previous studies conducted for single areas are simplistic. However, there is some consistency between areas. Avalanche frequency is most directly related to terrain steepness and snow supply. Average avalanche magnitude appears related to terrain steepness, starting zone, and track confinement and the scale (e.g., total vertical drop of the path) with only indirect evidence for a link to snow supply.