Abstract: In this study, we examine a physical raster-based distributed-parameter flood simulation model combining one-dimensional (1D) channel flow and two-dimensional (2D) overland flow. Continuity equations based on the water budget concept and momentum equations based on Manning’s formula are included. The Shihmen reservoir watershed, situated in northern Taiwan, is selected as the study site, and data regarding the passage of Typhoons Xangsane  and Nari  are utilized to test the model. Comparative analysis shows that the description of the riverbed obtained by the gradient method is superior to that obtained by the GIS approach. This study suggests the Thiessen polygon method to interpolate spatial precipitation. The best calibrations are obtained at a spatial resolution of 160 m × 160 m, with a simulated time step of less than 5 s. The case study indicates that the proposed model has a good potential for inflow description, but does not accurately simulate the inflow amount. The proposed model is a flash reacting event-based watershed model. To improve simulation accuracy, a good infiltration model and soil moisture model are needed, and their formulation could be our next task.