Numerical modeling of high-magnitude mass movement in data-scarce Himalayan terrain: a study using Lagrangian based modified DualSPHysics tool

Abstract

This study presents a high-resolution numerical simulation of the 2017 Kotrupi debris flow in Mandi, (India) using the fully Lagrangian Smoothed Particle Hydrodynamics (SPH) method implemented in DualSPHysics. To better capture the complex behavior of granular debris flows in steep Himalayan terrain, a modified Herschel–Bulkley–Papanastasiou (HBP) rheological model was employed, incorporating a pressure-dependent yield stress based solely on the internal friction angle (ϕ), while cohesion (c) was set to zero in accordance with the predominantly coarse, non-cohesive material observed at the site. The simulation reproduced key flow characteristics including runout distance, flow depth, and infrastructure impact, notably aligning with field reports of damage to National Highway NH-154. Temporal evolution of velocity, hydrodynamic pressure, and energy distribution revealed strong agreement with post-event assessments and improved fidelity over previous mesh-based or semi-empirical models. These findings underscore the value of frictionally calibrated SPH models for debris flow hazard assessment in data-scarce mountain regions. The work offers a reproducible, open-source framework that supports future integration with rainfall triggers, automated source area extraction, and regional-scale risk analysis for infrastructure planning. © The Author(s), under exclusive licence to Springer Nature B.V. 2026.