Hydrodynamic Flow and Sediment Transport in Bended River with the Presence of Islands

Abstract

【Objective】 Some rivers have islands. Their soil composition and geometrical shape influence water flow and sediment transport in the rivers. The purpose of this paper is to study the impact of flow rate and flowing duration on sediment erosion and hydrodynamic flow in a bended river. 【Method】 The study is based on two-dimensional average shallow water flow and sediment transport over riverbeds. Both water flow and sediment transport are solved using the MIKE 21. The model is applied to the section of Yellow River at Yongfeng Ferry in Ningxia province, where there are several small islands. 【Result】 When water flows for 3 hours at rate of 1 545 m3/s, sediment erosion reduces water velocity by 0.06~0.27 m/s and water depth by 0.02~0.32 m, compared with the results calculated without considering sediment erosion. Continuous erosion tends to stabilize water depth and flow rate. The deepest erosion depth is 0.16 m after water flows for 3 hours at rate 1 545 m3/s, and this increases to 0.24 m after the flow is increased to 6 hours at the same rate; their associated maximum deposition depth is 0.12 m and 0.23 m respectively. With the increase in flow rate and flow duration, the riverbed stabilizes, though erosion depth and deposition thickness continue to change. 【Conclusion】 Sediment erosion increases the stability of hydrodynamic flow in the river, and the riverbed morphology does not change after flow rate exceeds a critical rate. These simulated results are consistent and can be used to help improve river management.

Keywords

• yellow river
• sediment
• riverbed erosion
• continuous bend
• numerical simulation