This paper introduces a new high temporal resolution suspended sediment routing model that integrates fine sediment deposition and re-entrainment processes of individual size fractions with suspended sediment transport throughout the river network. This multi-size fraction model provides unique insights into the effects of sediment size classes on key sediment attributes, including suspended sediment size distribution and total concentration, sediment load, and changes in riverbed deposited fine sediment throughout the river network. Data from three high-frequency flow and sediment monitoring sites on the Manawatū River, New Zealand, were used to test the model. After calibrating the model using data from one flood event, it showed good agreement between observed and modelled fine sediment concentration and event load for five subsequent test events. When coupled with catchment erosion predictions, this new sediment routing model should provide valuable information on sediment sources and connectivity within catchments for informing catchment management.