Coupled modeling of bed evolution and bank deformation in the braided reach of the Lower Yellow River

Abstract

<p indent=0mm>Floodplains on both sides of the braided reach in Lower Yellow River (LYR) are extremely wide, accounting for 80% of the total channel area, and large channel deformation occurs during the flood season in this reach. Thus, bed evolution and riverbank deformation are typical characteristics of channel evolution in the braided reach of LYR. To calculate riverbed evolution and riverbank deformation, a one-dimensional coupled model, which includes three modules for hydrodynamics, sediment dynamics, and bed evolution, bank erosion, and accretion, is proposed. The proposed model was used to simulate the longitudinal and lateral deformation in the braided reach of LYR in 2006 and 2018 to conduct detailed processes of model calibration and verification. Results indicate the following. (1) The proposed model can accurately simulate flow and sediment transport processes. The Nash-Sutcliffe efficiency coefficient (NSE) between calculated and measured values of water discharges, water levels, and sediment concentrations was above 0.6, with a maximum value of 0.97. (2) The riverbank accretion and erosion widths were roughly calculated, and the relative errors between the calculated and measured reach-scale riverbank widths were less than 1.5%. (3) Analysis of the effect of riverbank deformation on longitudinal deformation revealed that riverbank accretion and erosion calculation modules played an important role in the calculation of flow, sediment transport, and riverbed evolution in the braided reach of LYR.