Pedological discontinuities as potential factors of shallow landslides

This research work is part of a wider research project (PONOl-01503: "Integratedsystems for hydrogeological risk monitoring, early warning and mitigation alongthe main lifelines"), aimed at hydro-geological risk mitigation and early warningalong three highway sections of southern Italy. In particular, the main resultssummarized here are focused on the assessment of shallow landslide susceptibilityalong the A3 highway section between Cosenza Sud and Altilia in northernCalabria.A detailed geological and geomorphological survey allowed us to map the mainlithological, structural and relief features of the landscape, with a special emphasison active, dormant and inactive landslides and their gee-lithological controlfactors.A soil survey was also carried out in the field, showing a domina nee of Entisols andInceptisols on steep slopes, and Mollisols and Alfisols on gentle landforms. Soilobservations were focused on the identification of pedological discontinuities aspotential factors that might trigger shallow landslides. A number of soil profiles,often close to landslide scarps, evidenced significant morphological changes ofthe parent materials, such as texture, pedogenic structure, dry consistence andmoisture, or hydromorphic features caused by transient water-logging conditions,and clay-illuviated horizons. Buried soils were recognized, often truncatedby erosion, and overlain by younger soils developed on colluvia, debris flows anddetrital slope deposits.Five representative soil profiles were selected and sampled for both pedologicaland geotechnical laboratory analyses. Bulk and undisturbed samples were collected,(i) for chemical and physical soil analyses (particle size distribution, organicand inorganic carbon, pH, electrical conductivity, soluble salts), and (ii) fordetermining bulk density, Atterberg limits, cohesive strength, angle of internal friction, water retention and for thin sections to be observed under an opticalpolarizing microscope, respectively.Preliminary results of laboratory analyses showed irregular patterns of both pedologicaland geotechnical data along the soil profiles, coherently with field observations.