Mapping rapid-moving landslide with satellite SAR images: the case of Montescaglioso (South Italy)

Pre-event and event landslide deformations have been detected and measured for the landslide that occurred on December 3rd, 2013 on the south-western slope of the Montescaglioso village (Basilicata Region, Southern Italy). The event, triggered by 56 h of continuous rainfalls, produced a ground displacement of several meters and created significant damages to buildings and local infrastructures. Ground displacements have been mapped through an integrated analysis based on a series of high resolution SAR (Synthetic Aperture Radar) images acquired by the Italian constellation of satellites COSMO-SkyMed. The purpose of this mapping activity was twofold: (i) detect and record any pre-event deformation in and around the village of Montescaglioso, through the use of multi-image SAR interferometry, suitable for mapping slow deformation phenomena and (ii) map and measure any surface changes produced by the 3rd December landslide, using amplitude-based method, suitable for mapping much faster displacements. SAR Interferometry, applied to images taken before the event, revealed a general pre-event movement, in the order of a few mm/year, in the south-western slope of the Montescaglioso village, with highest velocities in the sector of the slope where the first movement of the landslide took place. Amplitude analysis allowed the retrieval of the three components of the landslide deformation field, with values exceeding 10 m for large sectors of the landslide area and local peaks of 20 m in its central and deposit areas. The synergistic exploitation of phase and amplitude of SAR images turned out to be a powerful tool for landslide investigation, allowing the detection of slow, precursory deformation patterns as well the retrieval of full 3D surface displacement fields caused by large, rapid-moving landslides.