Artificial cavities and sinkholes in the hydrographic district of the Southern Apennines of Italy: findings, architectural variability and risk assessment.

he territory managed by the Hydrographic District of Southern Apennine (Autorità di Bacino Distrettuale dell’Appennino Meridionale - ADAM), in southern Italy, is subject to highly critical situations of the physicalenvironmental system and risk induced by natural and anthropogenic phenomena; the geological hazards include those connected to the presence of cavities in the subsoil. These represents a serious problem, especially in intensely urbanized areas where the stability of urban structures is often compromised by the presence of underground voids, locally forming a well developed network of cavities , produced by decades of excavation activities. Aimed at developing a District Basin Plan and the related Management Plan relating to the topic of Cavities, a scientific collaboration agreement was signed between the ADAM, the Department of Earth and Environmental Sciences of the University of Bari Aldo Moro (DiSTeGeo) and the Engineering Department of the University of Campania Luigi Vanvitelli (DI). Objectives of the research project are the census, analysis and evaluation of the cavity system on the territory of the district. An accurate research was conducted as regards all documentary sources that could provide information on the presence of cavities. The great heterogeneity of the data acquired made it necessary to identify a homogenization and cataloguing system to be connected to the classification provided by the National Commission on Artificial Cavities of the Italian Speleological Society (Galeazzi, 2013; Parise et al., 2013), which takes into account the construction typologies and those structural elements susceptible to trigger sinkholes. Since the municipalities included in the District are 1632, a “topdown” approach was chosen for the identification of the presence of possible artificial cavities, starting from the analysis of the Lithological Map of Italy and selecting those lithologies potentially affected by activities of excavations. The data were managed in a GIS environment; through the creation of queries, information was obtained about the spatial distribution of cavities of anthropogenic origin by municipal area. In parallel with the activities described above, data relating to documented sinkholes that occurred in the ADAM territory were collected, deriving from previous studies (above all the DiSTeGeo chronological catalogue; Vennari & Parise, 2022) and research commissioned by the Civil Protection Service of Apulia. By analyzing the available data, the spatial distribution of the documented sinkholes connected to artificial cavities was obtained throughout the territory considered. The work is still in progress and many portions of the territory are still without data, or need to verify what has been identified with the survey framework set out herein. However, the acquired data is populating a DB which will constitute a unique document in Italy, including all aspects relating to artificial cavities which will form the basis for subsequent analyses, aimed at defining procedures for preliminary evaluation of the stability conditions of artificial cavities, detailed assessment at two pilot areas within the ADAM territory, including modeling analyses, and to establishment of actions addressed toward mitigation of the risk related to sinkholes.