A Simple Model for the Variability of Release Area Size

Abstract

The hazard mapping tool NAKSIN estimates the release probability of potential release areas (PRAs) by testing a stability criterion based on the infinite-slope approximation with a large sample of synthetic weather situations. The release area is thus assumed to comprise the entire PRA, which is unrealistic for avalanches with return periods shorter than 100–300 y. To remedy this, a stability criterion is proposed that accounts for stabilizing forces across the slab perimeter and so is sensitive to the slab extent. The criterion is applied to a sequence of subareas of the PRA with increasing minimum slope angle to find the subarea with maximum release probability. The method is described and formulated mathematically. Also, tools for coding it are suggested but implementation in NAKSIN and testing are left for future work.