Integrated monitoring system GB-InSAR and Terrestrial Laser Scanner for Mont de La Saxe landslide, Italy

A careful description of the failure mechanisms is fundamental for the understanding of landslide evolution and a quantitative hazard analysis, assessment and mitigation. A complete kinematic characterization of the landslide ground surface allows to attain a description and zonation in terms of displacement and deformation paths. A robust and complete displacement field might be obtained by correlating a series of multi-temporal observations performed by means of terrestrial laser scanning and ground-based interferometric radar surveys. We investigate the Mont de La Saxe landslide (8 million m3, Aosta Valley Region, northern Italy), on the left-hand side of Ferret Valley within a deep-seated gravitational slope deformation. This landslide is one of the most investigated and monitored in the European Alps. A complete monitoring dataset exists since 2009. Because of its location just above Entreves and La Palud villages and its proximity to the Mont Blanc highway tunnel and to the Mont Blanc cableway, this landslide poses an extremely high risk. The evolution of the ground surface displacements is monitored by means of optical targets, a fixed and time-lapse GPS network, a ground-based interferometer and periodic Terrestrial Laser Scanner surveys. Distribution of displacements at depth is monitored by multi-parametric borehole probes (2D-DMS columns) and borehole wire extensometers. In this contribution we discuss the advantages of the comparison and mutual integration of ground-based radar interferometric data (daily-acquired) and Terrestrial Laser Scanner data (monthly-acquired). Therefore, the comparison is performed between a monitoring system, characterized by a high-accuracy (millimetric), near real-time monitoring capability and with no morphological information (i.e. GB-InSAR), and the TLS system, characterized by low-accuracy (centimetric) with a laborious post-processing but with an important morphological content. In particular, we use this data to analyze the temporal evolution of the landslide during the last 3 years with a main focus on the April 2014 crisis (max displacement rate of ca. 1000 mm/day).