The Impact of Land Subsidence on Preservation of Cultural Heritage Sites: The Case Study of Aquileia (Venetian-Friulian Coastland, North-Eastern Italy)

In the north-western coastland of the Adriatic Sea flooding hazard due to land subsidence and eustasy seriously jeopardizes the many cultural heritage sites present in the area, among which the UNESCO site of Aquileia. Located about 10 km inward from the coastline, Aquileia has recently come to the fore for the severe structural damages caused to its Patriarchal Basilica by differential ground subsidence. This study aims at highlighting the main control factors for subsidence in Aquileia framing it in a regional context. Our investigation is based on the integrated analysis of vertical displacements from Persistent Scatterers Interferometry and levelling surveys from the literature along a N-S transect from Terzo D'Aquileia to Grado. Interpretation of results is based on a geotechnical reference model of the subsoil obtained mainly from borehole data. Beside confirming the regional subsidence scenario affecting the Venetian-Friulian coastland, our study indicates that in Aquileia, differences in subsidence rates between the archeological area and the new city likely relate to diverse consolidation paths induced in the subsoil of the two sites by differential and diachronous man-mad loading over historical time. The smaller scale yet stark variability of sinking rates observed at the Patriarchal Basilica are interpreted to relate to heterogeneities in the shallow subsoil.