Characterization and geotechnical investigations of a riverbank failure in Florence, Italy, UNESCO world heritage site

On May 25, 2016, an artificial riverbank of the Arno River collapsed just upstream from the famous Ponte Vecchio bridge in the city of Florence, Italy, a UNESCO World Heritage Site. An analysis of the failure was performed to identify the damage condition of the involved structures, to define the causes of the failure, and preserve the site. This study was based on borehole integration and geotechnical characterization, terrestrial laser scanner (TLS) and digital photogrammetry (DP), bathymetric and geophysical surveys, riverbank stability analysis, and wall seismic vibrations assessment. The TLS survey results were used to characterize the three-dimensional (3D) wall deformations pattern, the landslide geometry, and to define the involved volumes. The riverbank stability analysis demonstrates that the lower safety factor was obtained in the case of complete saturation of filling materials and low river level in accordance with the major cause of collapse being attributed to the loss of water from subterranean pipes.