Mapping Starting Zone Snow Depth with a Ground-Based LIDAR to Improve Avalanche Control and Forecasting

The distribution of snow depth in avalanche starting zones exerts a strong influence on avalanche potential and character. Extreme depth changes over short distances are common, especially in wind-affected, above-treeline environments. Snow depth also affects the ease of avalanche triggering. Experience shows that avalanche reduction efforts are often more successful when targeting shallow trigger point areas near deeper slabs with explosives or ski cutting. Our paper explores the use of highresolution (cm scale) snow depth and snow depth change maps from terrestrial laser scanning (TLS) data to quantify loading patterns for use in both pre-control planning and in post-control assessment. We present results from a pilot study in three study areas at the Arapahoe Basin Ski Area in Colorado, USA. A-Basin has a large number avalanche starting zones above treeline at elevations up to 4,000 m. The areas represent a range of institutional avalanche management history – the East Wall has been operated since 1970, Montezuma Bowl since 2008, and the Steep Gullies are under study for area expansion. A summer TLS survey produced a zero depth surface. Mapping multiple times during the snow season allowed us to produce time series maps of snow depth and snow depth change at high resolution to explore depth and slab thickness variations due to wind redistribution. We conducted surveys before and after loading events and control work, allowing the exploration of loading patterns, slab thickness, shot and ski cut locations, bed surfaces, entrainment, and avalanche characteristics. We also evaluate the state of TLS for use in operational settings.