Comparing methods for estimating β points for use in statistical snow avalanche runout models

Snow avalanche runout estimates are core to risk assessment and mitigation for infrastructure development and transportation corridors in mountain regions. Two statistical models, the Runout Ratio model and the alpha-beta model, estimate the extreme runout position using the point where the slope of the avalanche path centerline first reduces to ten degrees (β point). In North America, the β point has traditionally been determined through a field survey of the avalanche path runout zone; however, as they become more accessible, digital elevation models (DEM) are increasingly being used to determine β as part of a preliminary review. While DEM requirements have been identified in avalanche literature, more focus is required on reviewing field error and relating the two methods.We surveyed 53 paths in western Canada, and estimated a field error distribution for the β point with an interquartile range of ± 2% of path length and a maximum range of ± 6.5% of path length. Five DEMs were sourced with spatial resolutions ranging from 1 m to 90 m. Of these, a 10 m DEM generated the most similar β point estimates to the field survey.