Sinkhole monitoring and early warning: an experimental application of ground-based interferometry

At Il Piano (Elba Island, Central Italy) 11 sinkhole events occurred on 9 different points on or close to a strategic road connecting Rio Marina to the rest of the island. In order to reduce the risk, a ground-based interferometric radar has been experimentally installed to detect possible precursor deformations of the ground. In this paper we present the results of a test simulating the occurrence of a sinkhole, which highlighted the criticalities of the method, and the successful prediction of a sinkhole event that could have endangered people travelling along the road. These experiences constitute a very important premise and confirm the possibility to measure precursor deformations even days before the opening of a sinkhole. This is due to the presence of a cover consisting in plastic material (clay, silt and even the street tar) that experiences a deformation before rupture as the sinkhole propagates from the bedrock.