AVALANCHE HAZARD MAPPING WITH SATELLITE DATA AND A DIGITAL ELEVATION MODEL

Since avalanche hazard mapping is a very time-consuming affair, it is our objective to develop an appropriate method to map large remote areas. This is based on satellite imagery and on a digital elevation model (DEM) tested at two sites in the Swiss Alps. To simulate the avalanche hazard, the existing Salm-Voellmy model was modified for the computer environment and extended to include the characteristics of avalanches within forested terrain. The forests were classified with Landsat Thematic Mapper (TM) data. So far, only a single forest class has been established. While the separation of forest, shrub and non-forested areas near the timberline poses problems, the classification of small openings and avalanche tracks inside the forest was successful. Comparison with the existing avalanche cadastral map revealed that 85 per cent of the risk areas were correctly classified. Separation into the defined 'red' and 'blue' danger zones, on the other hand, was not satisfactory. For an operational application, further improvements are necessary. However, the general approach is very promising and should lead to more reliable hazard maps for planning purposes, as well as to new and better insights into the mutual interactions between snow and forest.