Morphological and kinematic evolution of a large earthflow: The Montaguto landslide, southern Italy

We studied the geomorphological evolution of the Montaguto landslide, a 3.1 × 103 m long earthflow in the southern Apennines of Italy. Following an analysis of the different methods and techniques available to measure surface modifications caused by a large earthflow, we selected a combination of monitoring techniques compatible with the Montaguto case study. We exploited: (i) visual interpretation of aerial and satellite imagery, (ii) quantitative analysis of six digital elevation models (DEMs) covering the landslide area, and (iii) a large set of high-accuracy three-dimensional topographic measurements captured by three robotised total stations (RTSs). Integration of the results obtained from the different monitoring techniques allowed us to investigate the long (multi-decadal) and short (seasonal) term evolution of the Montaguto earthflow in the 58-year period (1954-2011). The examination of the available aerial, satellite and hill-shade images revealed a cyclic, long-term behaviour of mass movements of different types in the Rio Nocelle catchment occupied by the recent Montaguto earthflow. The combined analysis of the six DEMs allowed measuring the material eroded from the landslide crown area (V ~ 1.4 × 106 m3) and deposited in the landslide toe area (V ~ 1.2 × 106 m3) in the period from 2005 to June 2011. The analysis of a large set of high-accuracy topographic measurements revealed the kinematical characteristics of different sectors of the active earthflow, and allowed the reconstruction of the temporal and spatial evolution of the moving failure. The insights obtained are significant for the geo-mechanical modelling of similar earthflows, regional landslide mapping, and the evaluation of hazard and risk posed by large earthflows in southern Italy or similar physiographic regions.