Hydro-Stratigraphic Conditions and Human Activity Leading to Development of a Sinkhole Cluster in a Mediterranean Water Ecosystem

Abstract

Salento Peninsula (Apulia, southern Italy) is characterised by many active sinkholes, which represent the main geological hazard. The stretch of coastline between the village of Casalabate and Le Cesine wildlife reserve is highly affected, with a system of dunes separating the low beach from extensive wetlands, which were subject to uncontrolled urban development after reclamation. The overall morphology is characterized by flat topography, whilst from a hydrogeological standpoint, the mixing of inland freshwater with advancing brackish water favours the higher aggressivity with respect to soluble rocks, and the development of enhanced dissolution (hyperkarst). The relict landscapes within the protected areas still allow for the recognition of actively occurring sinkholes, which cause damage to houses, the road network and infrastructures. In this article the case of Aquatina di Frigole is described, where in the last 15 years numerous sinkholes have formed, with the processes still in rapid evolution. Detailed surveys allow for to identification of the mechanisms of sinkhole formation (suffusion sinkholes), the deriving cluster, and the main hydrogeological links among the different water bodies in the area. Acquatina di Frigole provides an excellent natural laboratory to observe development and evolution of sinkholes, and their relationships with the stratigraphic and hydrogeological elements.