EDDA 1.0: integrated simulation of debris flow erosion, deposition and property changes

Abstract

Abstract. Debris flow material properties change during the initiation, transportation and deposition processes, which influences the runout characteristics of the debris flow. A quasi-three-dimensional depth-integrated numerical model, EDDA (Erosion–Deposition Debris flow Analysis), is presented in this paper to simulate debris flow erosion, deposition and induced material property changes. The model considers changes in debris flow density, yield stress and dynamic viscosity during the flow process. The yield stress of the debris flow mixture determined at limit equilibrium using the Mohr–Coulomb equation is applicable to clear water flow, hyper-concentrated flow and fully developed debris flow. To assure numerical stability and computational efficiency at the same time, an adaptive time stepping algorithm is developed to solve the governing differential equations. Four numerical tests are conducted to validate the model. The first two tests involve a one-dimensional debris flow with constant properties and a two-dimensional dam-break water flow. The last two tests involve erosion and deposition, and the movement of multi-directional debris flows. The changes in debris flow mass and properties due to either erosion or deposition are shown to affect the runout characteristics significantly. The model is also applied to simulate a large-scale debris flow in Xiaojiagou Ravine to test the performance of the model in catchment-scale simulations. The results suggest that the model estimates well the volume, inundated area, and runout distance of the debris flow. The model is intended for use as a module in a real-time debris flow warning system.

Deciphering controls for debris‐flow erosion derived from a LiDAR‐recorded extreme event and a calibrated numerical model (Roßbichelbach, Germany)

“…Begueria et al, 2009;Hussin et al, 2012). The explanatory power of physical debris-flow properties has been implemented in predictive models using flow velocity (Takahashi et al, 1992) and shear stresses (Chen and Zhang, 2015;Frank et al, 2015), but these are rarely validated by real events. A momentum-dependent erosion rate has been described for ice-rock avalanches (Schneider et al, 2010), but the transfer to debris-flow erosion processes is not straightforward.…”

EDDA 2.0: integrated simulation of debris flow initiation and dynamics considering two initiation mechanisms

“…10a. The most eroded areas during the Xiaojiagou debris flow event were in channels, where a huge amount of loose solid material was present (Chen et al, 2012). Loose deposits on the hillslopes also eroded after the landslide bodies detached from their original locations and slid down the slopes.…”

“…1). After the Xiaojiagou debris flow, detailed field investigations and laboratory tests were conducted (Chen et al, 2012), as well as numerical back analysis . The study area is divided into four zones .…”

“…As the surface runoff accumulates the landslide dam formed earlier in the channel may break, initiating a channelized debris flow (e.g. Liu et al, 2009;Chen et al, 2012;Peng and Zhang, 2012). At the same time, the surface runoff may cause bed erosion and initiate hillslope debris flows (e.g.…”

“…The final magnitude of a debris flow could be many times that of its initial volume due to entrainment of materials along the path from additional slope failures, bed erosion, or bank collapses (e.g. Iverson et al, 2011;Chen et al, 2012;Ouyang et al, 2015). If the debris flow reaches a flat residential area downstream in the basin, it can cause severe loss of life and property.…”