Engineering Geological Analyses for Hazard Assessment of the Urbanized, Relict Lemeglio Coastal Landslide (Eastern Liguria, Italy)

Abstract

The relict Lemeglio coastal landslide is a deep-seated mass movement, involving heterogeneous flysch rock-masses. The landslide is characterized by a complex evolution and composite mechanisms, which were activated under past morphoclimatic conditions and controlled by different mechanical behaviours of the involved geological formations. Despite the current global slope stability, the accumulation zone is still prone to residual movements as it has been recognized since the last decades by diffuse damages suffered by buildings constructed over the landslide foot. To safeguard the urbanized area, different types of remedial works have been carried out through time, which varied from deep drainages to structural measures. This study investigates the engineering geological setting of the landslide body and its current kinematics to assess landslide hazard. For such a purpose, interferometric (PSInSAR technique) and inclinometric monitoring data were analysed. Among the principal results is the characterisation of the landslide accumulation zone, which is still active down to a depth variable from 13 to 48 m. In this area, the maximum recorded ground velocities varied from 24 to 6–8 mm year⁻¹ in the past two decades. This very slow slope deformation regime affecting an urbanized area is a valuable example for both focusing the residual hazard related to a relict landslide and designing effective remedial works consistently to an engineering geological and kinematic model. The proposed case study arouses challenging issues about the appropriate choices for planning of urban areas in this uncertain type of geohazard.