© Proceeding of the 21st LAHR-APD Congress 2018. All rights reserved. Debris flow simulation is an effective method for understanding the behavior and influence of debris flows. This simulation allows for effective countermeasures such as sabo facilities and evacuation planning. This study focuses on the Mt. Sinabung volcanic region of North Sumatra, which has recently experienced increased eruptive activity. Given that a landslide dam was formed upstream of the main torrent at Mt. Sinabung, debris flow scenarios arising from the outburst need to be considered to predict and prevent damage in downstream regions. For the simulation, we applied KANAKO system with a 2 m resolution DEM for landform setting. To set the supplied discharge, we applied a rational formula using recorded rainfall data. We observed that the constituent material of the riverbed was relatively small-sized with regard to the field surveys. The larger portion of the sediment constituting approximately 35% of the riverbed ranged in particles sized from 0.05 to 0.3 m. The other 65% of the sediment was fine-grained smaller than 0.1 mm. Recent studies have indicated that the debris flows that contained a high concentration of fine particles had a higher flow-ability and larger fluid phase density than stony debris flows. Therefore, we considered scenarios involving fine materials that contributed toward a larger fluid phase density. We also considered scenarios without considering the effect of fine materials. Based on the results, the debris flow scenario considering the fine material effect appeared to flow down for a long distance and exhibited a higher risk at the downstream side.