Reconstructing Debris Flow Events and Dynamics in the Northern Apennines, Italy: A Multi-Disciplinary Approach Linking Ground Evidence with Climatic Triggers

Debris flows are among the most common natural hazards in mountainous regions, with the potential to severely impact human lives and infrastructure. In the vicinity of the Alpe di Succiso Mountain (Northern Apennines, Italy), several debris flows have been documented, impacting trees in the upper portion of the forest. As the precipitation events can become more intense in relation to climate change, assessing the spatial distribution through time of these debris flows is essential for modeling their occurrence and for effective hazard assessment. In the context of the DECC project (2023), on the N-facing slope of the Alpe di Succiso we set up a multidisciplinary research comprising geomorphology, dendrochronology, geopedology, hydrological monitoring and climatology. Geomorphic processes of different types (glacial, gravitational and torrential) characterize the area and have shaped landforms and deposits since the late Quaternary (Rashid et al., 2024). Being the soil a useful archive of forming factors leading to its development, two different soil toposequences (one along a stable slope and one along the slope affected by debris flow) have been selected and analysed using a geopedological approach. The study of the spatial variation of soil profiles in relation to their position along the slope allows the reconstruction of both the stability and instability phases that characterise the slope over time and the impact of debris flows on soil development. The first results coming from the four hydro-pedological stations show that all the monitoring points respond quickly to precipitation, highlighting the presence of a highly permeable soil. During the summer season, thanks to high temperatures and relatively sparse rainfall events, the soil tends to dry out after rain. However, in early autumn, due to the drop in air temperatures and more frequent and intense rainfall events, it consistently exhibits conditions of complete saturation for extended periods. Based on dendrogeomorphological analysis and orthophotos, the debris flow events were classified into major and minor categories. The 1975 and 1987 events were classified as major, while the 1997, 2003, and 2013 events were considered minor. Debris flow events were further correlated with precipitation records from various sources, including hydrological yearbooks, nearby weather stations, and rain gauge based and reanalysis gridded datasets. In this context we are investigating several rainfall events which could have triggered debris flows through time.