Author(s): Matteo Barbini; Stefano Lanzoni; Carlo Gregoretti
Linked Author(s): Carlo Gregoretti
Keywords: Debris flow; Entrain and deposition process
Abstract: Stony debris flow is one of mountain areas' most hazardous natural phenomena. It is characterised by a solid-liquid surge that moves downstream under the effect of gravity. The hazard is due to the high velocity and the transport of a large amount of sediment, mainly gravel and sand, with boulders of large size up to 5 m and more. Therefore, stony debris flows have a significant destructive potential that threatens human lives and infrastructure. Stony debris flows usually initiate in the high-sloping reach of channels incising the slopes, where abundant runoff following short duration and high-intensity rainfalls can entrain a large quantity of sediments along the channels, forming a surge with a solid-liquid head and a fluid body. The surge routes downstream, entraining sediments, and forming a solid-liquid current. Any hazard assessment or mitigation works planning requires determining the impact of stony debris flows, which can be achieved using numerical models. The literature includes several models to simulate debris flow propagation, each emphasizing specific aspects or types of debris flow. This research presents a hydraulic bi-phase 2D model for the stony debris-flow propagation based on the Shallow Water Equations, that adopt a collisional rheology typical of stony debris flows. The model simulates the deposition and entrainment processes using an empirical equation proposed by Egashira et al. (2001) and amended later by Gregoretti et al. (2019). In each time step, the numerical scheme implemented to solve the equations is a first-order central finite volume scheme. The system of equations (1) is composed of five equations: two mass conservation equations, one for the total volume and one for the solid volume; two momentum conservation energy equations along the x and y directions; the Exner equation for mass conservation of the exchange of sediment with the bed.
Year: 2025