JiJi Weir was built across a mountain river, Chuoshui Creek, Taiwan. Because of deep slope, abundant sediment supply and tropical Typhoon climate, channel changes are very fast and occur in Typhoon seasons. Since its normal operation in 2002, the shallow reservoir of the JiJi Weir had a serious sediment problem: it could be filled up in just one strong typhoon event. Sediment will be completely carried through the reservoir and the spillway of the Weir. In this paper, a computational model, CCHE2D, was used to simulate the sediment transport of the JiJi Weir Reservoir. Transport of both suspended load and bedload sediments with multiple grain-sizes was simulated, and the geomorphology changes were studied within the reservoir during nine typhoon events. Simulation results were compared with the measurements of morphological change, and it shows that the CCHE2D model is capable of producing reasonable and realistic morphological changes.