Assessment of slow deformations and landslide modelling in the urban area through a multi-methodological approach

Slow-moving landslides are widespread in the Mediterranean area, causing damage to the exposed facilities and economic losses in many countries. The recognition of slow-moving landslides in urban areas is always a difficult task to deal with because the presence of buildings, infrastructures, and human activities usually conceals the morphological signs of these landslide activities. So, in the last decades, numerous researchers have shown new methodologies to deepen the studies of similar instability phenomena. The present research is based on an integrated approach to investigate the landslide boundaries, type of movement, failure surface depth, and vulnerability state of buildings in Rota Greca village (Calabria region, southern Italy) affected by a slow-moving landslide. For this purpose, multi-source data were acquired through geological and geomorphological surveys, recognition of landslide-induced damage on the built environment, subsurface investigations (e.g., continuous drill boreholes, Standard Penetration Test, Rock Quality Designation index and inclinometer monitoring), laboratory tests (direct shear tests on undisturbed samples), geophysical survey, and InSAR-derived map of deformation rates. The complete integration of multi-source data allowed for the construction of reliable landslide modelling with relative geotechnical properties. In addition, the cross-comparison between surface deformation data by SAR images and severity damage level collected on the exposed buildings enabled to obtain the vulnerability map of the built area. In particular, the achieved goals highlighted two failure surfaces at about -13 and -25 m depth, causing a high vulnerability value for the buildings allocated in the central portion of the Rota Greca village. The knowledge acquired by the multi-approach can be used to manage and implement appropriate landslide risk mitigation strategies, providing helpful advice and best practices to state run organisations and stakeholders for landslide management in urban sites.