A spatially distributed Xinanjiang model (DXAJ) has been developed to simulate the hourly hydrological process of a storm event caused by Typhoon No. 11 during the period of the 22–23 August 2001 in the Kamafusa Lake catchment, Miyagi Prefecture, Japan. The catchment is divided into 50 × 50 m2 grid cells, and the runoff generation component of the Xinanjiang rainfall-runoff model is applied to each grid cell. An optimal routing order approach is used to implement the distributed routing, i.e. the runoff generated in each grid cell is routed together with upstream inflow from upstream grid cells to downstream grid cells according to the optimal routing order, which is derived from a simulated stream network. One process-based soil erosion model is coupled onto this distributed hydrological model to simulate suspended solids generation in each grid cell and generated suspended solids are routed together with runoff from upstream grid cells to downstream grid cells. The simulation results are in good agreement with the observed hydrograph and pollutograph. The soil erosion simulation was improved through the consideration of rainfall intensity in the soil erosion model. Copyright © 2003 John Wiley & Sons, Ltd.