Linking spatial patterns of catchment-averaged denudation rates with sediment connectivity in Alpine catchments

Landscape evolution is driven by the patterns and rates of sediment transfer between the hillslope and the fluvial domains, and along the river network. The efficiency of sediment transport through the sediment cascade is controlled by the spatial configuration of landforms and the sediment connectivity between the geomorphic domains. In mountainous environments, large volumes of sediment are mobilized on hillslopes by e.g. mass-wasting and glacial processes. However, the mobilized sediment will be efficiently transported downstream only if sediment connectivity within river catchments is high. The latter therefore has potential impacts on denudation rates quantified at the catchment scale.

In this contribution, we explore the potential link between sediment connectivity and catchment-wide denudation rates in the Upper Rhone valley. To achieve this goal, we implemented an automatic workflow to compute the topography-based sediment connectivity index from Cavalli et al. (2013) using digital terrain models with a spatial resolution of 2 m, and to process spatial information on connectivity at the regional scale. We quantified sediment connectivity for 32 tributary catchments of the Upper Rhone, for which catchment-wide denudation rates are reported in the literature. We then contrasted sediment connectivity with denudation rates and discuss the spatial pattern of our results with data on mass-wasting processes.