Sinkhole development along the Apulian coastlines, within the framework of the project Fu.Co.Ka. (Future scenarios in Coastal Karst)

This abstract is dedicated to studying coastal karst areas in Apulia focusing on the effects deriving from the dissolution processes acting at the interface between freshwater and saltwater, within the framework of the PRIN project “Future scenarios in coastal karst: saltwater intrusion, loss of water resources and sinkhole development as effects of climate changes (Fu.Co.Ka.)”. Apulia is among the most remarkable karst regions in the Mediterranean Basin, with over 80% of its territory constituted of soluble carbonate rocks outcropping, and about 900 km of coastlines. It represents therefore an ideal place where to study the climate change impacts on coastal karst, and which outcomes might be useful for other coastal areas, in the Mediterranean as well as in other parts of the world. The high fragility of coastal karst is related to its hydrogeological peculiar characteristics, the direct link between the surface and the underground, and the facility in contaminating the groundwater and in favoring the development of sinkhole processes. In this latter regard, the presence of karst voids poses the need to investigate the instability processes, and their effects at the surface. Within caves, the rock materials are strongly susceptible to water-induced weathering processes, which are responsible, first, of local failures, and, through progressive stopping, may later reach the ground surface in the form of different types of sinkholes (Gutierrez et al., 2014; Parise, 2019, 2022). Assessing the stability of underground karst caves is a complex task, due to the variety of involved factors, the many uncertainties in predicting the cave evolution, and the likely interaction of the instability features with the overlying infrastructures at the surface. This latter is a very important issue in highly attractive tourist sites such as the coasts of Apulia. The main driving factors for sinkhole occurrence in coastal settings are detected through investigations with DTMs and detailed mapping, characterization of local geology and geomorphology, and geo-structural surveys. Detailed surveys are being carried out using advanced laser scanning devices, integrated by drone flights for the outside environments, aimed at searching for correlations between surface features, evidences of instability (subsidence, flooded areas, erosion, sinkholes), cave levels and underground morphologies. This activity may also contribute to reconstruct the evolution of the water table, and its relationship with the landscape evolution, both at the surface and underground. A specific focus is further given to documentation of some of the precursory signs of likely failures in cave systems, such as extrusion wedges and bulging from the walls, that may represent the first warning signs for future sinkholes. Given the relevant role of seastorms in the triggering of cliff failures and coastal sinkholes, this aspect, too, is taken into account for a full understanding of the driving forces acting on the examined coastal stretches.