Debris flow simulation 2D (DFS 2D): Numerical modelling of debris flows and calibration of friction parameters

Debris flows are rapid mass movements with a mixture of rock, soil and water. High-intensity rainfall events have triggered multiple debris flows around the globe, making it an important concern from the disaster management perspective. This study presents a numerical model called debris flow simulation 2D (DFS 2D) and applicability of the proposed model is investigated through the values of the model parameters used for the reproduction of an occurred debris flow at Yindongzi gully in China on 13 August 2010. The model can be used to simulate debris flows using three different rheologies and has a user-friendly interface for providing the inputs. Using DFS 2D, flow parameters can be estimated with respect to space and time. The values of the flow resistance parameters of model, dry-Coulomb and turbulent friction, were calibrated through the back analysis and the values obtained are 0.1 and 1000 m/s², respectively. Two new methods of calibration are proposed in this study, considering the cross-sectional area of flow and topographical changes induced by the debris flow. The proposed methods of calibration provide an effective solution to the cumulative errors induced by coarse-resolution digital elevation models (DEMs) in numerical modelling of debris flows. The statistical indices such as Willmott's index of agreement, mean-absolute-error, and normalized-root-mean-square-error of the calibrated model are 0.5, 1.02 and 1.44, respectively. The comparison between simulated and observed values of topographic changes indicates that DFS 2D provides satisfactory results and can be used for dynamic modelling of debris flows.