Reconstructing human-induced geomorphic changes through historical maps and multitemporal remote sensing data in the Cancano–San Giacomo di Fraele reservoirs (Central Alps, Italy)

This paper investigates human-induced geomorphological transformation along the Fraele Valley (Central Alps, Northern Italy) following the construction and operation of the Cancano I, San Giacomo di Fraele and Cancano II hydroelectric dams. By integrating historical maps (1866-1931), aerial imagery (1945-1954), declassified satellite data, recent remote sensing products and field geomorphological mapping, we reconstruct the evolution of the Adda River corridor from a natural braided river system to a regulated and largely submerged hydrographic network. The results show that the original fluvial landforms, characterized by debris-flow fans, gravel bars and dynamic channels, were progressively submerged and reworked by reservoir development and seasonal water-level fluctuations, promoting the formation of fan deltas, shoreline gullies and subaqueous landforms and redirecting sediment fluxes into the artificial basins. Field surveys during an exceptional low-lake level in 2023 improved remote-sensing interpretations, revealing submerged landforms, reactivated drainage pathways and localized shoreline erosion. These multiscale observations highlight how repeated water-level oscillations act as a key morphodynamic driver, enhancing sediment reworking and slope-reservoir nexus. This work contributes to the understanding of anthropogenic geomorphology in high-mountain regions, underscoring the value of combining remote sensing data, historical cartography and field evidence to assess large-scale and subtle diachronic transformations of the Alpine catchment. The study highlights the need for integrated approaches to evaluate long-term landscape change and geomorphic feedbacks in regulated mountain catchments.