Abstract
Predicting bedload fluxes in Alpine river systems is extremely challenging due to the complexity of sediment dynamics and the difficulty of quantifying bedload to support model development. Traditional methods to predict bedload rates and volumes rely on the calculation of bedload transport capacity at individual river sections, assuming unlimited sediment supply. This often leads to large overestimations of transported volumes and an inability to capture actual network-scale dynamics. To overcome these caveats, we have adapted the network-scale sediment transport model D-CASCADE for application to steep, coarse-bedded mountain river systems. We introduced different approaches to estimate flow hydraulics and sediment transport capacity. We evaluated the model at a single cross-section using 6 years of continuous bedload measurements at the outlet of the Sulden/Solda river basin (Italian Alps). The model was run using two different assumed channel widths; mean-flow and bankfull; resulting in over- and underestimations of measured bedload, respectively. Despite this, the adapted model predicted annual bedload volumes at the catchment outlet within one order of magnitude of the measured values, consistently better than using the traditional approach. We then used the model to assess longitudinal connectivity, transport rates, sediment storage dynamics and bedload budgets along the whole Sulden river network, comparing model predictions qualitatively against the available information on channel dynamics for the same period. These comparisons highlight the model’s ability to reproduce key geomorphic processes, supporting its value as a novel approach for estimating sediment fluxes in Alpine river systems. Data suggest that the adapted D-CASCADE model can provide realistic spatial and temporal patterns of sediment transport and storage, aligning well with observations across the network.