Regional Mountain Conference

Alpine catchments are characterized by steep topography and high relief energy, favouring active sediment transfer and natural hazards such as debris flows. Sediment connectivity theories provide a promising framework for understanding geomorphological processes and dynamics, making structural sediment connectivity a key indicator for sediment flux patterns at the catchment scale. DEM‑based indices such as the Index of Connectivity (IC) are widely used to map sediment pathways, but their empirical validation against field‑based connectivity assessments remains has hardly been investigated to date, which represents a relevant research gap within sediment connectivity theories.

In this study, a new field index for structural sediment connectivity is developed to provide a rapid, simple, robust and reproducible method for mapping sediment connectivity patterns in alpine environments. The index is designed for application along transects within alpine catchments and captures key topographic and sedimentary features that control sediment transfer over steep slopes and channels. It is implemented in two alpine catchments in Tyrol, both characterized by similar land use and surface cover and documented to have experienced debris flows in recent years, providing a suitable setting to test the method under comparable morphological conditions.

The field index is compared with the IC calculated from a 2018 high‑resolution DEM using the SedInConnect Tool, with the aim of assessing whether the field‑based method can serve as a potential “ground truth” for remotely derived connectivity patterns. Results indicate broadly consistent spatial patterns in steep terrain, whereas the field index highlights local sediment traps and depositional features that are not always reflected in the IC. Overall, it confirmed the patterns identified by the IC, which represents a decisive step in the validation of such indices.

The study demonstrates that the proposed field index offers a practical, standardized and reproducible approach for assessing structural sediment connectivity at the catchment scale in alpine catchments. It provides a methodological basis for further validation and refinement of remote‑sensing‑based connectivity indicators and contributes to improving the empirical foundation of sediment connectivity and hazard assessments in mountain regions.