SOIL features and pedogenic processes as predisposing factors of SHAllow landsliDES (SOIL SHADES)
Progetti
Referente interno: Massimo Conforti
Email: massimo.conforti@cnr.it
The project proposal aims at the assessment of the relationship between key soil properties (as result of peculiar weathering and pedogenic processes) and predisposing factors of shallow landslides, and the analysis of landslide susceptibility in a pilot catchment of Calabria, southern Italy. Main objective is the understanding of the trigger mechanisms of shallow landslides in a defined environmental context, to propose a benchmark protocol for the evaluation of landslide hazard. This will be a basis for the definition of best practices of management interventions and risk mitigation, especially in view of ongoing climate changes and future scenarios, characterized by increasing frequency and impact of extreme meteorological events. We will apply an integrated multidisciplinary, multianalytical and multiscale approach, combining traditional and innovative pedological analyses with geological, geomorphological and geotechnical investigations. Our planned approach encompasses remote and proximal sensing, field surveys at catchment, hillslope and pedon/soil profile scale, in situ tests and laboratory analyses ranging from petrography, mineralogy, geochemistry, geotechnics, hydrology, geophysics to rock and soil micromorphology. The effects of weathering and pedogenesis on the modification of the main physico-chemical, mineralogical, macro- and micromorphological properties of different parent materials over time will be investigated. A special emphasis will be given to the differentiation of the weathering/soil profile into pedogenic horizons, whose properties may cause a differential response in terms of soil hydrology, geomechanics and rheological behavior. In other words, we will explore how and to which extent pedogenic changes might act as macro/micro-discontinuities and preferential sites for potential creation of failure surfaces and thus trigger shallow landslides. This will be done by applying a horizon-wise sampling strategy that enables to catch the intrinsic vertical spatial variability of soils and any specific features of different genetic horizons, which are well-known to soil scientists but often neglected in geological and engineering geology studies. Major geotechnical and rheological properties (bulk density, total porosity, Atterberg limits and consistency indices, shear strength) as well as hydrological properties (water retention, pore size distribution, hydraulic conductivity) will be determined and compared with pedological data (particle size distribution, clay minerals, clay dispersivity, geochemical composition and weathering/pedogenic indices). Evaluation of all mutual relationships between data obtained from such varying methods and disciplines will contribute to predict areas potentially prone to soil-involving landslides. An attempt to include pedological properties, both at catchment and hillslope scale, in the evaluation of shallow landslide susceptibility and corresponding maps, will be achieved as well.
This project have a high impact for the advancement of knowledge in the assessment of shallow landslide hazard, because most of the research studies and applications focused on this topic have so far neglected the key role that pedogenic features and associated weathering/soil-formation processes may have in the trigger of such phenomena. Indeed, pedogenesis can change substantially the geomechanical behavior of the parent rock, which cannot be any more considered as such in slope stability modeling and applied technical interventions. Moreover, it may create discontinuities within the soil profile that need to be taken into great account as well. This has relevant implications at different levels: 1) sampling strategy and choice of adequate laboratory analyses for the characterization of soil material properties; 2) correct selection and implementation of prediction models, and quantitative evaluation of slope instability; 3) proposal and achievement of adequate slope stabilization or restoration measures; 4) production of suitable hazard maps useful for stakeholders, and planning of efficient policies of prevention, mitigation and management of the hydrogeological risk by decision makers; 5) improvement of the life quality and safety of citizens, and protection and defense of human lives; 6) preservation, sustainable exploitation and valorization of the soil georesource and associated ecosystem services.