Predicting debris flow pathways using volume-based thresholds for effective risk assessment
A. Rajaneesh, V. K. Krishnapriya, K. S. Sajinkumar, Nikhil Nedumpallile Vasu, Cees van Westen, Thomas Oommen, Ali P. Yunus, Vanessa Banks, A.P. Pradeepkumar
Abstract
Investigating the preferential flow path of a debris flow is crucial for quantifying the risk and developing mitigation strategies. Here, we examined 66 debris flows from the Western Ghats in India employing Rapid Mass Movement Simulation (RAMMS)::Debris Flow software to understand the kinematics of run-out. Our analysis revealed that the debris flow run-out in the study area follow two main routes: 60 along the existing stream channels (SC) and six following the steepest hill slope (SH). We further simulated these debris flows to identify their drivers, and derived a threshold that distinguishes between SC and SH-type debris flows. Our results indicate that the debris flow volumes greater than 7072 cu. m is SH-type, whereas those with smaller volumes are more likely to follow SC paths. The model’s accuracy was validated against field observations, achieving a success rate of 93% for SH-type flows and 85% for SC.