The use of spatially distributed erosion and sediment yield models has become a common method to assess the impacts of land-use changes within catchments and determine appropriate management options. Lack of model validation is, however, increasingly recognised as an issue, especially for models applied at the large-catchment or regional scale. The present study applies the spatially distributed erosion and sediment yield model SedNet to a 6000-km2 subcatchment of the Fitzroy River in central Queensland, Australia. Model outputs are compared with the results from sediment-source tracing, measured floodplain deposition rates and available hydrometric station data. Results indicated that significant improvement can be made to model predictions when catchment-specific observations (such as river bank and gully geometry and gully erosion history) are used to refine model-input parameters. It was also shown that the use of generic input parameters used by previous SedNet applications within the Great Barrier Reef catchment area resulted in overestimates of sediment yields. Previous model applications may have overestimated the significance of post-European catchment disturbance on the sediment yields of the dry-tropical catchments draining to the Great Barrier Reef. Our findings illustrated the value of obtaining empirically derived data to validate spatially distributed models applied at large scales.