Resistivity and induced polarization surveys for slope instability studies in the Swiss Alps

A geoelectrical investigation has been carried out in the Swiss Alps (near the Dent de Nendaz within the southern part of the Rhone valley in the Swiss Alps) to delineate groundwater circulation within an unstable slope. This unstable zone is characterized by a landslide area with clear scarps and hummocky ground at the bottom of the slope. Large scale apparent resistivity mapping provided information on the main pathways for water transport within the slope. Subsequently, 2D resistivity and induced polarization imaging supplied details on the region of instability located at the bottom of the slope. Polarizable units identified in the region of instability could be linked to a clay-rich unit or to local enrichment of graphite within the bedrock. Our results illustrate how low permeability clay/graphite units and permeable water-bearing units could be distinguished using a combined interpretation of resistivity and IP data in slope instability studies.