Numerical simulation for braided rivers with erodible banks

Abstract

Understanding the process and mechanism of morphological behavior in braided rivers is very important for river engineering purposes to manage hydraulic structures and prevent disaster from flood, and environmental purposes to maintain river ecosystem and landscape. A two-dimensional numerical model was developed to simulate braided rivers with erodible bed and banks composed of well sorted-sandy materials. A moving boundary-fitted coordinate system was employed to calculate water flow, bed change, and bank erosion. CIP (Cubic Interpolated Pseudo-particle) method was used to calculate flow, which introduced little numerical diffusion. Sediment transport equation in the streamline and transverse wise, considering the secondary flow, was used to estim ate bed and bank evolution in time. Bank erosion was simulated when the gradient in the cross-sectional direction of the banks was steeper than the submerged angle of repose because of the bed erosion in the vicinity of banks. Braided river in laboratory was reproduced for verifying the numerical model in the channel filled with nearly uniform sandy materials. Comparison of numerical results and experimental data has shown relatively good agreements.