Landslide monitoring for risk mitigation by using corner reflector and satellite SAR interferometry: The large landslide of Carlantino (Italy)

The use of satellite Synthetic Aperture Radar Interferometry (InSAR) for monitoring ground instability due to landslide events, although advantageous over large spatial scales, still poses challenges related to the recurrently complex kinematics of the phenomena or to the unfavorable settings of the examined areas with respect to steep topography and vegetated land cover. This paper presents results obtained by using Multi-temporal InSAR techniques with high resolution TerraSARX (TSX) data for monitoring the Carlantino landslide, located in the Daunian Subapennine (Apulia region, southern Italy) on a slope overlooking a water reservoir, and subjected to several investigations and consolidation works. The targets detected by using Persistent Scatterer Interferometry (PSI) correspond to urban structures or peri-urban walls and guard rails, while the landslide body is almost completely devoid of stable targets, due to the widespread vegetation and variable land cover. To allow stability monitoring, a network of six Corner Reflectors (CR) was designed and deployed over the landslide test site. The TSX images were analyzed by using both the PSI processing and a procedure, based on the double difference analysis of InSAR phase values on the CR pixels. Despite residual noise and the loss of 2 CRs due to vandalism, the processing allowed verifying the stability of the upper and central part of the landslide body, and relating indirectly the movements at the toe of the landslide to the water level fluctuations of the reservoir. Finally, this experiment suggests some recommendations and guidelines in planning CR deployment in complex landslide sites.