Snow-avalanche hazard assessment based on dendrogeomorphic reconstructions and classification tree algorithms for ski area development, Parâng Mountains, Romania

Abstract

This paper explores the snow-avalanche regime based on tree-ring reconstructions and their triggering weather conditions with classification tree algorithms.The results show a significant increased frequency of avalanche events on Zăvoaie NE slope for the second half of the 20th century by comparison to the Scărița SW slope. The classification tree models highlight the weather conditions leading to avalanche release with three scenarios in each path. The first scenario underlines the wind's effect as a key weather variable on both slope aspects. The second scenario corresponds to a spring regime, while rain and warm temperatures are the main triggers. The third general weather condition favouring snow avalanche activity are persistent low temperatures and important snowfall throughout the winter season. However, this triggering condition was mainly found on the NE avalanche path, probably related to the pattern of snow accumulation, the prevailing winds, but above all the lower solar radiation which favours a slower and later melting of the snow cover. Finally, the return periods and runout distances calculated from tree ring analysis show a high risk for the location of the infrastructure planned for the ski area expansion, showing once again the usefulness of dendrogeomorphology in natural hazard assessment where historical data are lacking.