The response of very small glaciers to climate changes is highly scattered and little known in comparison with larger ice bodies. In particular, small avalanche-fed and debris-covered glaciers lack mass balance series of sufficient length. In this paper we present 13 years of high-resolution observations over the Occidentale del Montasio Glacier, collected using Airborne Laser Scanning, Terrestrial Laser Scanning, and Structure from Motion Multi-View Stereo techniques for monitoring its geodetic mass balance and surface dynamics. The results have been analyzed jointly with meteorological variables, and compared to a sample of “reference” glaciers for the European Alps. From 2006 to 2019 the mass balance showed high interannual variability and an average rate much closer to zero than the average of the Alpine reference glaciers (−0.09 vs. −1.42 m water equivalent per year, respectively). This behavior can be explained by the high correlation between annual balance and solid precipitation, which displayed recent peaks. The air temperature is not significantly correlated with the mass balance, which is main controlled by avalanche activity, shadowing and debris cover. However, its rapid increase is progressively reducing the fraction of solid precipitation, and increasing the length of the ablation season.

This study presents an inventory of sediment source areas updated to 2016 of the Rio Cordon catchment, a small headwater basin located in the Eastern Italian Alps. The aim of the 2016 inventory was to update an old sediment source areas dataset dating back to 2006, built using LiDAR-derived geomorphometric parameters interpretation and field survey, in order to evaluate the geomorphic changes occurred in the last 10 years in the catchment. The new inventory was realized by means of an extensive field survey campaign conducted with a mobile GIS mounted on a rugged notebook integrating a GPS receiver. Pictures of individual or collective sediment source areas were also acquired in order to integrate the GIS dataset and to better define their current status of activity. The images were also used for a comparison with the images acquired in 2006 to identify the evolution or stabilization of each sediment source area. The identification and delimitation of large and/or unreachable areas was carried out in the office by interpreting aerial photo images (Bing satellite images and Web Map Services for AGEA 2009-2012 aerial photographs, compared with the old LiDAR-derived high resolution images used for the 2006 sediment source inventory). The comparison with the previous inventory shows that several old sediment sources resulted totally stabilized indicating a general decrease of erosion processes in the catchment. In contrast, some new sediment source areas were identified. They were mainly related to a very recent rock fall that took place in July 2016 in the Lastoni di Formin group and many new shallow landslides were found in the upper part of small Rio Cordon tributary where a small debris flow event occurred in 2012. © Società Geologica Italiana, Roma 2017

Structure-from-Motion (SfM) photogrammetry is increasingly employed in geomorphological applications for change detection, but repeatability and reproducibility of this methodology are still insufficiently documented. This work aims to evaluate the influence of different survey acquisition and processing conditions, including the camera used for image collection, the number of Ground Control Points (GCPs) employed during Bundle Adjustment, GCP coordinate precision and Unmanned Aerial Vehicle flight mode. The investigation was carried out over three fluvial study areas characterized by distinct morphology, performing multiple flights consecutively and assessing possible differences among the resulting 3D models. We evaluated both residuals on check points and discrepancies between dense point clouds. Analyzing these metrics, we noticed high repeatability (Root Mean Square of signed cloud-to-cloud distances less than 2.1 cm) for surveys carried out under the same conditions. By varying the camera used, instead, contrasting results were obtained that appear to depend on the study site characteristics. In particular, lower reproducibility was highlighted for the surveys involving an area characterized by flat topography and homogeneous texturing. Moreover, this study confirms the importance of the number of GCPs entering in the processing workflow, with different impact depending on the camera used for the survey.