Sinkholes in the Tagliamento river Valley: the case study of Quinis Village

In the Tagliamento Valley (NE Italy) are present several situations related to sinkholes and subterranean voids threatening the built-up environment above, as the Quinis village. In particular many absorption points occurred in the Enemonzo municipality. This last one committed to the researchers of the Trieste Univ. and OGS institute a multidisciplinary study in order to define and outline the sinkholes phenomena and to individuate the triggering factors. The historical analysis permitted firstly to identify the phenomena evolution during the last century, the cases that took to the demolishment of the existing buildings, among which there was also the church, and the ones that today are still causing instabilities. This allowed to realize a monitoring network for the unstable infrastructures and a defined geophysical and hydrogeological monitoring program. To better understand the groundwater flow mechanisms and to try to define the intrinsic vulnerability of the different areas a multidisciplinary approach was adopted. A groundwater monitoring network consisting of several multiparametric devices (electrical conductivity, temperature and water level) was implemented. Water samples were collected and geochemical analysis performed. Two wells were equipped with assestimeters. The groundwater table has huge variations between dry and rainy seasons and also between two different precipitation events. Geological and geomorphological surveys jointly with the stratigraphical data and geophysical ones (seismic, ERT and GPR techniques) permitted to deeply investigate the area and to reconstruct the bedrock and the quaternary deposits above. Quinis village lies on fluvio-glacial and alluvial deposits with an estimate thickness of 6 - 40 meters. The northern part of the study area, characterized by the outcropping of evaporitic units (Upper Carnic), is widely affected by caves, voids and dolines. The present study illustrates the state of the art on the sinkhole knowledge in Enemonzo municipality and shows how a broad spectrum investigation can help in identifying safer areas for a more conscious future territorial planning.