Post-mobilization experimental evaluation of Tangni Debris flow in Garhwal Himalaya, India

This study investigates the runout and depositional behavior of the Tangni debris flow in the Garhwal Himalaya, India, through a series of controlled experiments conducted at the newly developed facility at CSIR-Central Building Research Institute, Roorkee. The experiments focused on evaluating the influence of water content, initial volume, and grain size distribution on debris flow dynamics. Debris flow experiments reveal that small changes in water content can trigger abrupt transitions in flow regimes, significantly altering runout distances and deposition patterns. Additionally, dimensionless parameters were calculated to characterize flow regimes, and granulometric analysis was performed on the deposited material. The results show that runout distance and deposition area increase with higher water content and larger initial volumes, whereas finer content reduces runout. Granulometric analysis revealed a clear segregation of coarse particles, with enrichment at the margins and towards the flow front, indicating that coarse particles enhance the destructive potential of debris flows. Dimensionless analysis identified the experimental flows as predominantly frictional in nature. The findings demonstrate consistency with natural debris flows and align with global experimental studies, providing valuable insights into the behavior of debris flows in the Indian Himalayas. Despite limitations due to scaling effects and reconstruction challenges, this study highlights the importance of experimental approaches in advancing our understanding of debris flows, particularly in regions lacking extensive historical data and monitoring infrastructure.