Abstract
On 4 November 2010, a deep-seated gravitational slope deformation (North Italy) reactivated with sudden ground movement. A 450,000 m2 mountainous area moved some metres downslope, but the undeniable signs were only connected to the triggering of a debris flow from the bulging area’s detrital cover and the presence of a continuous perimeter fracture near the crown area. Based on two detailed LiDAR surveys (2 m × 2 m) performed just a few days before and after the event, a quantitative topographic analysis was performed in a GIS environment, integrating morphometric terrain parameters (slope, aspect, surface roughness, hill shade, and curvature). The DEMs analysis highlighted some morphological changes related to deeper as well as shallow movements. Both global and sectorial displacements were widely verified and discussed, finally inferring that the geometry, persistence, and layout of all movements properly justify each current morphostructure, which has the shape of a typical Sackung-type structure with impulsive kinematics. Moreover, a targeted field survey allowed specific clues to be found that confirmed the global deduced dynamics of the slope deformation. Finally, thanks to a ground-based interferometric radar system (GB-InSAR) that was installed a few days after the reactivation, the residual deep-seated gravitational slope deformation (DSGSD) movements were also monitored. In the landslide lower bulging area, a localized material progression of small entities was observed for some months after the parossistic event, indicating a slow dissipation of forces in sectors more distant from the crown area.
Highlights
Among natural hazards, slope instability processes in mountainous areas are characterized by complex interactions among different lithological, geomorphological, and structural features and processes [1,2,3,4]
This paper addresses the Rotolon deep-seated gravitational slope deformation (DSGSD), and the main goal is to understand its kinematic behaviour after the October-November 2010 rainfalls, which apparently does not show direct reactivation clues but only more hazardous localized and secondary phenomena such as debris flows and rock falls
Regarding its general structure, this slope deformation can be classified at the limit between large landslides and DSGSDs on the basis of the area-frequency statistics proposed by Agliardi et al [3]
Summary
Slope instability processes in mountainous areas are characterized by complex interactions among different lithological, geomorphological, and structural features (topographical location, size, and connection with the drainage network) and processes (triggering factors, styles of activity, and displacements) [1,2,3,4]. (iv) display gravitational morphostructures (e.g., large scarps and counterscarps or up-hill facing scarps, open or infilled trenches, downthrown blocks, ridge top depressions or toe bulging, open tension cracks, grabens, double or multiple ridges) [4,6,10,13,14] and geomorphological evidence of slope deformation and displacements along individual structures and inherited structural features [4] It is not yet clear if tectonic features play an active or passive role in DSGSD movements (i.e., DSGSDs occur in zones of high stress or in weak rock) [6]. A 3D landslide runout numerical model was used to identify the source and impact areas of potential debris flow events, flow velocity and deposit distribution within the Rotolon creek valley [16,33]
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