UAV-based topography and RAMMS-DF simulation for debris flow impact assessment: Insights from the typhoon Molave in Phuoc Thanh commune of Vietnam

Debris flows are among the most destructive hazards in mountainous regions, causing sudden and severe damage to people, infrastructure, and land. However, assessing their impacts remains challenging due to complex terrain conditions, limited ground observations, and the need for integrated spatial analysis. This study addresses these gaps by combining UAV-derived DEM, the RAMMS-DF model, and social infrastructure data to assess the debris flow event on October 28, 2020, in Phuoc Thanh commune, Da Nang City, Vietnam. RAMMS simulation produced maximum flow height, velocity, pressure, and deposition patterns, which were overlaid with infrastructure data in GIS. The results indicate that 22 houses, 6.64 hectares of agricultural land, 28.15 hectares of forest land, and 846.95 meters of road were affected, providing essential evidence for disaster planning. To resolve these issues, we implement a combined UAV-based topographic analysis and debris-flow modelling workflow. • UAV-derived DEM and RAMMS used to model 2020 debris flow in Phuoc Thanh. • Simulation reveals debris flow height, velocity, and deposition zones. • GIS overlay identifies impacts on homes, farmland, forests, and roads. • Findings support disaster planning and safer land-use in mountain regions.