Snow avalanche activity after fire and logging disturbances, northern Gaspé Peninsula, Quebec, Canada

Abstract

In mountainous areas, ecological disturbances causing forest fragmentation may influence the pattern and regime of snow avalanches. In the northern Gaspé Peninsula (Quebec), at two sites located on treed slopes of a south–north oriented valley, tree removal by fire and logging operations was the precursor factor for avalanche activity. Years of high-magnitude snow avalanches were identified based on tree-ring techniques; these avalanches were different from those identified by Dubé et al. (2004) for three undisturbed scree-slope sites in the same area. The lack of synchronicity in avalanche occurrences between disturbed and undisturbed sites suggests a strong influence of local factors (e.g., disturbance, local topography, slope aspect, vegetation). The first avalanche years were recorded in 1941 and 1988, after a fire in 1938 and logging operations in 1986–1987, respectively. Both of these years had above average snowfalls; this indicates that climate (total annual snowfall) was also a contributing factor for avalanche activity. The avalanche window in the post-logging site was shorter (four years) than that of the post-fire site (15–20 years). This is an indication that avalanche activity after tree removal largely depends on the capacity of woody vegetation to reach heights sufficient to control snow drifting and thus avalanche activity.