Terrestrial Laser Scanning (TLS) data for the analysis of coastal tuff cliff retreat: application to Coroglio cliff, Naples, Italy

In this study, we present the results of an analysis of Terrestrial Laser Scanning (TLS) datasets, referred to multi-temporal (2013-2015) acquisition, aimed at evaluating volumetric changes and average retreat rates of the Coroglio tuff cliff, located in the western area of Naples (Italy) in the Campi Flegrei caldera. The multi-temporal analysis was carried out in two steps: firstly, we developed a preliminary 3D Cloud-to-Cloud comparative analysis of point clouds obtained by TLS data processing, providing a view on geomorphological evolution; secondly, we obtained quantitative information by analyzing the differences between multi-temporal Digital Elevation Models. Finally, a morphometric analysis was carried out in order to evaluate both retreat and failure rates. Four types of landslides (rock fall, debris fall, earth flow, and soil slip) have been accurately mapped in the different sectors of the cliff. The morphological analysis shows that several morphological variations have been recognized in different areas of the cliff with a maximum retreat of 8 m at the foot of the cliff due to the erosive action of the sea on poorly lithified deposits. We estimated that the average linear retreat rate related to the Coroglio cliff between 2013-2015, was equal to 0.07 m/yr; the linear retreat rate is higher (0.34 m/yr) at the base of the cliff, directly beaten by the sea waves. The results of the statistical analysis of the relationship between volume and area calculated for rock falls are consistent with the results of previous studies. Geo-structural analysis confirms that some discontinuity sets strongly control the failure kinematics.