The Sediment Sources Availability Index: Application of a new semi-quantitative index to assess the potential connectivity of sediment sources at the catchment scale

The study introduces and applies the Sediment Sources Availability Index (SSAI), a new semi-quantitative method designed to assess the structural availability of sediment sources within mountain catchments. The method is applied to the Aurona creek catchment (Alpe Veglia, north-western Italian Alps), a paraglacial evolving basin strongly affected by glacier retreat. The research highlights the region's sediment cascade features, emphasising its structural connectivity characteristics. This catchment area is characterised by a complex interplay between various deposit types, influenced by ongoing climate change and permafrost degradation. Combining geomorphological mapping, field surveys, and high-resolution Digital Elevation Models, the SSAI integrates structural connectivity assessments and deposit characteristics to evaluate possible sediment sources and transport pathways. The framework combines the Index of Connectivity (IC) with the newly developed Erodibility index (Ei), which accounts for sediment granulometry and cohesion. Results highlight that sediment- source availability cannot be inferred from morphometric connectivity alone, highlighting the dual role of proglacial area landforms as sediment stores, barriers, and potential sediment sources. The SSAI provides a rapid first-order assessment of structural sediment availability, supporting sediment-cascade analysis, river manage- ment and geoconservation, while providing a robust basis for further functional sediment-connectivity investigations.