Combination of GNSS, satellite InSAR, and GBInSAR remote sensing monitoring to improve the understanding of a large landslide in high alpine environment

The investigation of large landslides in high alpine environments is often hindered by the difficult accessibility of the mountainous terrain. Efforts are typically concentrated on the remote measurement of the surface displacements, in order to define the general slope dynamics and identify phases of increasing activity. The characterization of such phenomena is challenging, due to their complex nature as well as the limitations of monitoring techniques. Appropriately integrating monitoring data from different sources can help reduce uncertainties, yet it is seldom done. In this paper, the outcomes of GNSS, satellite InSAR, and GBInSAR campaigns performed at the Bosmatto landslide (Northwestern Alps, Italy) are presented. The joint analysis provided a comprehensive view of the deformation field of the landslide, which revealed a gradually decreasing dip angle of the calculated movement vectors from head to toe. The instability was interpreted as a 2.5 – 3.5 ∗ 106 m3 rockslide, moving at peak velocities >50 mm/y according to a broadly roto-translational mechanism. The impact of the seasonal snow cover on the reliability of the interferometric acquisitions was also evaluated. Advantages and implications offered by the combination of multiple monitoring techniques are highlighted.