Item: The influence of topographic parameters on avalanche release dimension and frequency
Title: The influence of topographic parameters on avalanche release dimension and frequency
Proceedings: 2002 International Snow Science Workshop, Penticton, British Columbia
Authors: M. Maggioni and U. Gruber, WSL Swiss Federal Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland
Abstract: The avalanche hazard map zones in Switzerland are defined by the frequency and the impact pressure of a potential avalanche event Therefore, it is crucial to be able to. accurately estimate the release frequency and, related to the frequency, the release extent for a specific avalanche track. Up to now, avalanche experts have estimated these important input parameters based on their experience and on known historic avalanche events on an avalanche path. However, for most avalanche tracks only incomplete information about historic avalanche events is available, thus there is a large uncertainty concerning avalanche release frequencies and extents. In order to improve this knowledge, a statistical analysis of avalanche releases on well documented avalanche paths has been performed. In the region ofDavos, an almost complete database of avalanche events over the last 50 years exists, that covers not only frequent avalanche tracks but the whole area. Using Geographic Information System (GIS) technologies in combination with Digital Elevation Models (DEM), all avalanche release areas have been analyzed with respect to topographic characteristics. Topographic parameters like "slope", "confinement", "aspect" and "distance to the next ridge" are derived from the DEM. The statistical analysis results in general rules and probability distributions for release extents as a function of the frequency and the topographic parameters. The general rules are a valuable aid for the avalanche experts in cases where information about historic avalanche is lacking for a particular track. Furthermore, the probability distributions can be directly used as input for uncertainty modeling of avalanche run-out distances by Monte Carlo methods. In the avalanche winter of 1999 (in the European Alps), the latter topic has been shown to be very important for the further improvement of avalanche hazard maps and for the risk assessment of avalanche hazard in general.
Keywords: release area, topography, release frequency, geographic information systems (gis), statistics, avalanche cadastre
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