Sinkhole field above karst caves: detection and analysis through integrated techniques

The present work illustrates the results of studies in a sinkhole field at Nociglia (Salento subregion, Apulia, SE Italy) where the shallow phreatic speleogenesis operates close to the water table level with formation of karst caves, successive roof collapse, formation of wide caverns and sinkhole development. All of this creates serious problems to the nearby infrastructures, including a province road. Salento has a great number of active sinkholes, related to natural and anthropogenic cavities. Their presence is at the origin of several problems to the built-up environment, due to the increasing population growth and development pressures. In such a context, the detection of cavities, and the assessment of the sinkhole hazard presents numerous difficulties. A multidisciplinary approach, comprising geological, geomorphological and geophysical analyses, is necessary to obtain comprehensive knowledge of the complex phenomena in karstic areas. Geophysical methods can be of great help to identify and map the features related to the underground voids, likely evolving to sinkholes, by detecting contrasts in physical properties such as density and electrical resistivity, with the surrounding sediments. At the same time, recognition of the presence of sinkholes by geophysical methods has to adapt to the different geological conditions, and to take advantage of the integration among the several methodologies available.