<p>The estimate of suspended sediment load in rivers is often highly problematic because of the strong variability in suspended sediment concentrations with discharge. Previous studies that investigated the sources of this variability highlight the need to explicitly account for the main hydrological processes controlling sediment erosion and transport at the catchment scale, their spatio-temporal variability and interactions with the topography and surface characteristics of the basin. In this paper we propose a novel physically explicit spatially distributed hillslope erosion and sediment transport model including these erosion drivers, based on the computationally efficient hydrological model TOPKAPI-ETH. We investigate its suitability to reproduce the variability of sediment concentrations at the outlet of a pre-alpine river basin in Switzerland and quantify the impacts of key spatially variable erosion drivers – rainfall and surface erodibility – on sediment dynamics. Our analysis shows that deterministic modelling can capture a significant part of the variability in suspended sediment concentrations. Spatial variability of erosion drivers affects sediment yield by (i) increasing sediment production due to a spatially variable precipitation, while decreasing it due to a spatially variable surface erodibility, (ii) favoring the clustering of sediment source areas, and (iii) decreasing their connectivity to the river network by magnifying sediment buffers. Finally, we discuss the results in the context of the geomorphology and landscape characteristics of our study area and compare our findings with other modelling and empirical studies on sources of sediment concentration variability.</p>