Hydrogeology, Hydrochemistry and Isotopic Investigation to Define the Lateral Hydraulic Boundaries of a Deep Rock Slide (Berceto Landslide: Northern Apennines)

The Berceto landslide is a deep and active rock slide located in the northern Apennines. It affects a slope characterised by the overlapping of flysch and shale formations. The landslide has been monitored since the 1990s and an inclinometer installed in the head zone shows a sliding surface at the depth of 110 m. The landslide and the adjacent areas are affected by morphological anomalies in the slopes and in the surface drainage patterns. These anomalies are related to the presence of deep landslide or to the presence of faults in the bedrock. In particular, the River Baganza (RB) is situated at about 100 m upstream of the landslide main scarp and it is separated from the landslide by a thin layer of shale. The RB streambed is located at an elevation 70 m higher than the elevation of the active sliding surface. Due to these morphological anomalies, it is possible to speculate that the present extension of the landslide limit is not correct and that the landslide sliding surface could be extended as far as the RB. In this study, hydro-chemical and isotopic investigation have been carried out on the Berceto rock slide in order to define the lateral hydraulic boundary, the geometry of the slide surface and the groundwater flow paths. The ion contents and the δ18O-δ2H values indicate the presence in the landslide body of an external source of groundwater which could be provided by the RB through a sliding surface developed within the shale or by the flysch below the landslide body.