A multiscale framework for simulating landslide runout and impact with barriers

This study proposes a multiscale framework for simulating landslide runout and its impact on mitigation structures, particularly focusing on debris flows. The proposed methodology combines depth-averaged (DA) models for basin-scale flow propagation with three-dimensional (3D) models for detailed impact analysis. This multiscale approach effectively balances computational efficiency with the need for detailed simulation in critical areas, such as the barrier near-field. Validation is conducted using both laboratory-scale experiments and a real-world case study in the Italian Alps. The results demonstrate the capability of the framework to accurately replicate flow dynamics, including run-up, velocity profiles, and flow lamination operated by barriers. To our knowledge, this represents the first validated application of a DA-3D multiscale framework for debris flow-barrier interactions at the site scale. The study also introduces a novel 3D adaptation of the widely used Voellmy rheology, which allows consistent cross-scale parameterisation. This framework enables simulating debris flows at the site scale with a precision previously confined to the laboratory scale.