Multidisciplinary non-invasive investigations to develop a hydrogeological conceptual model supporting slope kinematics at Fontana Cornia landslide, Northern Apennines, Italy

A multidisciplinary approach focusing on the integration of diverse and non-invasive investigations is presented to define the hydrogeological conceptual model of the complex Fontana Cornia landslide in the Northern Apennines, Italy. The results of seismic refraction tomography and electrical resistivity tomography investigations indicate that the landslide has a curvilinear sliding surface dividing the shallow calcarenite debris layer from the deeper pelitic bedrock. The surface presents undulations in which water can be stored and supports the application of the fill and spill hypothesis that is seldom used in landslide studies. The joint interpretation of the geophysical outcomes and of the hydrogeological and hydro-chemical analyses of a spring located on the slope allows the definition of the landslide hydrogeological conceptual model. Four specific hydrologic stages with different groundwater flows though the landslide body were identified. The developed hydrogeological model may explain the displacements of the landslide that were detected with In-SAR monitoring. The isotopes analyses, the displacement monitoring, and the hydrogeological measurements confirm that periods with significant precipitations and snowmelt can cause an increase in landslide saturation that in turn triggers larger displacements. Conversely, the landslide slowly moves at a steady rate during periods with limited recharge water.