The RETURN project's approach to sinkholes, the most typical geological hazard in karst terrains

Within the framework of the RETURN (multi-Risk sci-Ence for resilienT commUnities undeR a changiNg climate) project funded by the Italian National Plan for Recovery and Resilience (PNRR), the Spoke2 “Ground Instabilities” aims at restituting temporal and space distribution of effects induced by ground instabilities (scenarios), i.e. landslides, sinkholes, subsidence and liquefaction. Preliminary results obtained for sinkholes are here reported, as these processes represent the most diffused geological hazard in karst areas. These are widespread in Italy in all areas characterized by outcrops of soluble rocks. Sinkholes are being analyzed in the project in terms of the predisposing factors as well as of preparatory and triggering processes. The distinction among them is made on a temporal basis: predisposing factors are considered invariable at the observation scale, while the preparatory factors show trends or periodic variations in the same time interval. As a consequence, a trigger is considered as a process which acts over a very short and well-defined time. Sinkholes are distinguished also on the basis of their kinematics, following the main internationally accepted sinkhole classification. The activities carried out in the first year of RETURN project brought us to collect a number of learning cases dealing with sinkholes in Italy, and to deduce rationales of process to be considered as tools for operative chains in view of the implementation of a scenario producer to be designed through an IT-technology. The outputs expected in the simulated scenarios are quantitative values attributed to ground instability effects (among which the sinkholes) in a multi-hazard perspective, with the final goal to offer multi-risk mitigation strategies to national stakeholders.