黄河下游河道滩岸崩退与淤长过程的耦合模拟

黄河下游滩岸变形时常发生，对河床稳定、防洪安全、滩区耕地保护等方面产生诸多不利影响，因此有必要在河道水沙数学模型中考虑滩岸变形计算。以一维水沙输移及床面冲淤计算模型为基础，结合滩岸崩退与淤长计算模块，建立了能同时模拟河床纵向冲淤与滩岸横向变形的耦合模型。采用该模型计算了黄河全下游（755 km长河道）的河床纵向与横向变形过程，选取2018年及2020年作为率定及验证年份对该模型进行测试。计算结果表明：该模型可以很好地模拟黄河下游滩岸崩退及淤长过程，黄河下游游荡段、过渡段、弯曲段河段平滩宽度的计算误差在2018年分别为4 m、5 m、1 m，三河段误差在2020年分别为12 m、14 m、4 m；黄河下游三河段滩岸变形程度差异较大，游荡段滩岸变形幅度远大于过渡段与弯曲段，过渡段与弯曲段变形幅度相差不大；三河段滩岸崩退幅度均大于淤长幅度，体现出下游河床呈现展宽的趋势；黄河下游滩岸崩退与淤长会对河床冲淤产生重要影响，其中游荡段滩岸变形对于河床冲淤影响较大，而过渡段及弯曲段的河床变形主要表现为水沙不平衡输移引起的床面冲淤。

Coupled Modelling of Bank Erosion and Accretion in the Lower Yellow River

Bank erosion and accretion often occurred in the Lower Yellow River (LYR), which led to several negative effects such as channel migration, safety of flood control, land loss. Therefore, it is essential to take the modules of bank erosion and bank accretion into account when calculating flow-sediment transport and channel evolution. A coupled one-dimensional model was proposed to simulate both bed evolution and bank deformation, including three modules of flow-sediment transport, bed deformation and bank erosion and accretion. The proposed model was applied to simulate the longitudinal and lateral channel deformations in the LYR with a length of 755 km, with the years of 2018 and 2020 being selected as the calibration and verification years to evaluate the model. The results indicate that: the proposed model can accurately simulate the processes of bank erosion and accretion, and the absolute errors between the calculated and measured post-flood reach-scale channel widths in the braided reach, transitional reach and meandering reach of the LYR were respectively 4 m, 5 m and 1 m in 2018 and 12 m, 14 m and 4 m in 2020; the bank deformation characteristics of the three reaches in the LYR were diverse from each other, with the deformation amplitude of the braided reach being much greater than that of the transitional reach and the meandering reach, and the deformation amplitude of the transitional reach and the meandering reach being almost the same. However, the amplitude of bank erosion in the three reaches was greater than that of the bank accretion, which reflects the trend of the channel widening in the LYR. The amounts of bank erosion and accretion were large in the LYR, and bank erosion and accretion had an important influence on channel evolution, among which bank deformation in the braided reach had an obvious contribution to channel evolution, whereas channel evolution in the transitional reach and meandering reach mainly came from the flow and sediment transport.