Monitoring Snow Cornice Development Using Time-Lapse Photography

A snow cornice is an overhanging mass of snow which generally forms on the lee side of ridges. Cornices can present a substantial snow avalanche hazard as they can trigger avalanches when they break. While the hazard posed by cornices has long been recognized and they are extensively con- trolled in avalanche operations, little research exists on cornice formation and failure. In this study, we used a time-lapse camera to monitor the growth and failure of a cornice during the 2013-2014 season. Images were taken at five minute intervals at a site which is instrumented with several automatic weather stations above the town of Davos, Switzerland. To compare the growth of the cornice with local meteoro- logical variables, we developed a method to automatically track the horizontal extent of the cornice based on converting the images to a binary format. Our results show that cornice growth only occurred during periods of moderate to high winds during or soon after snowfall. During the season we only observed a few small cornice failures, which mainly occurred after periods of rapid cornice growth. Finally, we com- pared our observed cornice extent to the wind drift index calculated by the snow cover model SNOW- PACK. The agreement between both was remarkable, suggesting that the SNOWPACK wind drift index can be used to quantify regional cornice growth.