Terrain Analysis and Monitoring of Large Deep-Seated Rock Slides in the Northern Apennines Using Integrated Ground-Based and Remote Sensing Techniques

Deep-seated landslides represent a major issue in geomorphology and engineering geology due to their complexity and potential impact on infrastructure and settlements. This study focuses on terrain analysis and monitoring of two large, complex deep-seated rock slides located in the Northern Apennines, in the municipality of Ferriere (Piacenza province, Italy). Both landslides (namely Colla di Gambaro and Brugneto) extend for more than 1 km in length and are characterized by roto-translational sliding of stratified arenaceous and silty rock masses (down to depths of more than 40 m), evolving into earth slides at the landslide toe. This makes the combination of conventional and remote sensing techniques essential for unreveal their characteristics and dynamics at the slope scale. An integrated approach was therefore adopted, using both existing and newly collected data. High-resolution DEMs from UAV surveys with LiDAR technologies and field surveys were integrated to delineate main landslide units and subunits based on combined geomorphological and kinematic criteria. The distinction of units affected by different movement rates and the evolution and propagation of movements downslope was greatly supported by InSAR displacement time series (obtained by both Permanent/Distributed Scatterers and Interferogram Stacking of Sentinel-1 satellite datasets) as well as continuous GNSS monitoring in some key points. Seismic surveys and inclinometers/piezometers, contributed to the identification of main sliding surfaces at depths and of the groundwater conditions. The integration of these techniques, improved the delineation of landslide boundaries, enhanced understanding of spatial variability in movement rates, and increased the accuracy of landslides mapping. Furthermore, it supported the construction of reference cross-sections that highlight the complexity of movements and movements rates at the slope scale, the transition from rock sliding mechanisms to earth sliding downslope. Maps and cross sections, ultimately, exemplify the geological and geotechnical model of these phenomena and demonstrate the added values of the combined use of conventional and remote sensing tools for enhancing our understanding of complex landslide phenomena, thus providing a basis for risk assessment and structural or non-structural mitigation strategies.