Abstract. In 1996 typhoon Herb struck the central Taiwan area, causing severe debris flow in many subwatersheds of the Chen-You-Lan river watershed. More severe cases of debris flow occurred following Chi-Chi earthquake, 1999. In order to identify the potentially affected area and its severity, the ability to simulate the flow route of debris is desirable. In this research numerical simulation of debris flow deposition process had been carried out using FLO-2D adopting Chui-Sue river watershed as the study area. Sensitivity study of parameters used in the numerical model was conducted and adjustments were made empirically. The micro-geomorphic database of Chui-Sue river watershed was generated and analyzed to understand the terrain variations caused by the debris flow. Based on the micro-geomorphic analysis, the debris deposition in the Chui-Sue river watershed in the downstream area, and the position and volume of debris deposition were determined. The simulated results appeared to agree fairly well with the results of micro-geomorphic study of the area when not affected by other inflow rivers, and the trends of debris distribution in the study area appeared to be fairly consistent.