Tree-ring reconstruction of high-magnitude snow avalanches in the northern Gaspé Peninsula, Québec, Canada

Abstract

In eastern Canada, snow avalanches are a common phenomenon, but their occurrences remain poorly documented. In the last 30 yr, they were responsible for deaths and damage to property and forests in avalanche-prone areas in northern and eastern Québec. This study provides tree-ring-based avalanche chronologies for three scree slope stands in the northern Gaspé Peninsula (Québec). Tree-ring records indicated that high-magnitude avalanches occurred seven times during the period from 1860 to 1997, i.e., in 1871, 1898, 1952, 1956, 1966, 1977, and 1996, with 5- to 15-yr return intervals for the period between 1939 and 1997. High-magnitude avalanches occurred during snowy winters, with total snowfall well above average (330 cm). According to the size of past runout zones established from damaged trees at the main study stand, snow avalanches were greater in 1956 and 1966 than in 1996. The 1996 avalanche area was about 16,600 m2 of which 60% (10,000 m 2) was covered with mature trees. It caused a ∼200-m recession of the tree line. Causal factors of snow avalanches including weather conditions and stand characteristics were also examined. © 2004 Regents of the University of Colorado.