Large-scale landslides often cause severe damage due to their long run-out distances and having disaster chain effects. Scenario simulation has been adopted in the current work to analyze the Xiaomojiu landslide dynamic processes, such as sliding velocity, deposition characteristics, and flood outburst after a landslide-dam failure using Particle Flow Code (PFC-3D) which introduced the changeable friction coefficient and the HEC-RAS software. The landslide characteristics and topography data were obtained via field investigation, whereas high-resolution topographic data (0.17 m) was obtained using an Unmanned Aerial Vehicle (UAV). The results showed that: 1. The landslide presents a scallop shape with a length of 1566 m, a width ranging from 809~1124 m, and an area of 1.34×10 6 m 2 . The average thickness and volume of the sliding body is approximately 40 m, 5.1×10 7 m 3 . The InSAR deformation analysis showed that the Xiaomojiu landslide has a maximum annual displacement rate of 60 mm/y, and a maximum accumulation deformation of 180 mm since November 25, 2017. 2. From the landslide simulation results, the failure process of the Xiaomojiu landslide lasted for 65 s with a maximum velocity of 78.2 m/s. The deposited area is approximately 2023 m long, 900 m wide, with a maximum height of approximately 149 m. 3. After the landslide blocks the Jinsha River, a landslide-dammed lake with an elevation of 2940 m and a storage capacity of 4.13×109 m 3 is formed. The maximum peak flow rate of the breach is 12051.7 m 3 /s, 43451.4 m 3 /s, 148635.6 m 3 /s, and 304544.7 m 3 /s for the landslide-dammed failure degrees of 15%, 25%, 50%, and 75%, respectively. These results provide a scientific reference for the risk analysis and mitigation of the landslide. KeywordsScenario simulation • Geohazards chains • Landslide failure • Flood simulation • Xiaomojiu landslide

Large-scale landslides often cause severe damage due to their long run-out distances and having disaster chain effects. Scenario simulation has been adopted in the current work to analyze the Xiaomojiu landslide dynamic processes, such as sliding velocity, deposition characteristics, and flood outburst after a landslide-dam failure using Particle Flow Code (PFC-3D) which introduced the changeable friction coefficient and the HEC-RAS software. The landslide characteristics and topography data were obtained via field investigation, whereas high-resolution topographic data (0.17 m) was obtained using an Unmanned Aerial Vehicle (UAV). The results showed that: 1. The landslide presents a scallop shape with a length of 1566 m, a width ranging from 809~1124 m, and an area of 1.34×106 m2. The average thickness and volume of the sliding body is approximately 40 m, 5.1×107 m3. The InSAR deformation analysis showed that the Xiaomojiu landslide has a maximum annual displacement rate of 60 mm/y, and a maximum accumulation deformation of 180 mm since November 25, 2017. 2. From the landslide simulation results, the failure process of the Xiaomojiu landslide lasted for 65 s with a maximum velocity of 78.2 m/s. The deposited area is approximately 2023 m long, 900 m wide, with a maximum height of approximately 149 m. 3. After the landslide blocks the Jinsha River, a landslide-dammed lake with an elevation of 2940 m and a storage capacity of 4.13×109 m3 is formed. The maximum peak flow rate of the breach is 12051.7 m3/s, 43451.4 m3/s, 148635.6 m3/s, and 304544.7 m3/s for the landslide-dammed failure degrees of 15%, 25%, 50%, and 75%, respectively. These results provide a scientific reference for the risk analysis and mitigation of the landslide.