Institute of Geography and Sustainability of the University of Lausanne
Permafrost - Bagnes
In order to consider the hazards associated to the mountain permafrost, the Municipality of Bagnes (VS) has commissioned the IGD to map the potential distribution of this phenomenon. The choice of a technique taking into account the strong spatial discontinuity of permafrost was necessary. Support Vector Machines (SVMs) have been chosen because of their ability to produce robust classifications. A dataset composed of 15 variables was selected for this model. Some were simply calculated and extrapolated from a digital elevation model (resolution 25x25 meters), whereas others have been extracted from the Swisstopo’s primary surface map and from a rock glacier inventory of the region. The dataset was completed by empirical measurements obtained during field campaigns. This innovative methodology has produced a model in line with the reality. A comparison with the official BAFU’s permafrost map has shown that the model provides a higher level of accuracy. A sectorial analysis was subsequently brought to light the main features of several areas potentially sensitive to hazards related to periglacial processes.