The degree of complexity in sediment cascades in relation to bedrock features in small mountain catchments - The case of the Buscagna catchment (Lepontine Alps)

The multiscalarity of mountain systems is mainly related to their complex structural settings that lead to the geological and geomorphological units fragmentation. This may have strong implications for the geomorphological evolution of the hydrographic basins, and the related sediment cascades. In the framework of this research, we characterized a small mountain catchment in the Lepontine Alps (North-Western Italy) through different techniques: geomorphological mapping, sediment connectivity assessment, and geomorphodiversity indexing. All these techniques allowed to obtain thematic maps to depict the influence of bedrock features on geomorphological evolution. The selected mountain catchment is drained by the Buscagna stream, which runs along the valley bottom separating two deeply different slopes. The northern slope (on the left hydrographic side) is constituted by very resistant gneissic rocks, while along the southern slope (on the right hydrographic side) soluble and fractured rocks (i.e., calcschist and marble) outcrop. The diversification of geomorphological processes is very evident and mirrored in the Geomorphodiversity and Fragmentation Index Maps. These properties of the relief proved to influence sediment connectivity patterns on the two slopes, as it emerges from the Index of Connectivity Map. The database of the geomorphological map realized at 1:10000 scale is set to include attribute fields for labelling each unit as source or sink elements, in order to create also a thematic map. The aim is to evaluate the degree of connectivity comparing morphometric indexing with geomorphological mapping and the other thematic map realized for the watershed, enhancing the role of bedrock in influencing structural and functional connectivity in a small mountain catchment.