Detecting mountain permafrost and hazard assessment for debris flows through the application of electrical resistivity tomography - an example from the Swiss Alps

A recendy deglaciated glacier forefield representing a potential starting zone of a periglacial debris flow was investigated using two-dimensional electrical resistivity tomography to charactcrise the subsurface lithology and to detect the presence/absence of permafrost. The results of the 2D resistivity surveys show that the moraine complex represents a periglacial debris reservoir which partly consists of frozen debris. The frozen (ice-bonded) part of the moraine is largely protected front sudden destabilization and retrogressive erosion can be assumed to be limited. Future degradation of the permafrost in the terminal moraine would enlarge the amount of erodible debris and generally reduce the mechanical stability. With the applied technique, permafrost or ground ice can be located with sufficient accuracy. On a local scale two-dimensional resistivity imaging could be used for a spatio-temporal monitoring of potential future changes in the permafrost extent and the depth of the active layer through repeated resistivity surveys.