Quantifying altimetric and volumetric changes of the Belvedere Glacier (2009–2023) using Pleiades and Pleiades Neo data

Abstract. The study presents a detailed photogrammetric analysis of the evolution of the Belvedere Glacier over the periods 2009–2017 and 2017–2023, with particular focus on the impact of the debris flow triggered by the flood event of August 27, 2023. High-resolution Pléiades and Pléiades Neo satellite imagery was used to generate point clouds and Digital Elevation Models, enabling the quantification of altimetric and volumetric changes and a detailed assessment of the morphological modifications caused by the debris flow. The results show a recent significant glacier retreat, with an average annual volume loss of 2.3 × 10⁶ m³/year between 2009 and 2017, increasing to 2.7 × 10⁶ m³/year between 2017 and 2023. The 2023 debris flow produced marked morphological changes, including the formation of two accumulation zones on the western tongue and the development of two erosional channels approximately 4–5 meters deep. These channels resulted from the new course of the Castelfranco Stream, which incised directly into the glacier surface. Overall, the findings confirm trends reported in previous studies on the Belvedere Glacier and other Alpine glaciers, highlighting the importance and advantages of satellite-based monitoring for assessing the impacts of climate change and extreme events on glacier dynamics.