In the section of the Middle Yellow River from Longmen to the Sanmenxia Dam, the prediction to hyperconcentrated flood processes is difficult because of the abrupt change of channel geometry along the river and the high variability of the amount of flood water and sediment load from the main river and tributaries. A river network model based on a Godunov-type FVM scheme is proposed in order to investigate the flow dynamics, sediment transport and bed evolution during hyperconcentrated floods. A quasi 2D algorithm is adopted to calculate the velocity at the junction cell, which is then used for providing the interior boundary conditions. The computation for each reach can be executed simultaneously and the solution procedure is parallelized using OpenMP. The speedup factor compared with a serial program increases linearly in theory with the number of reaches in the river network. Two flood events, featuring significant erosion and deposition respectively, were simulated to validate the model. The calculated water levels, discharges and fractional concentrations of non-uniform suspended load were in agreement with the measurements. A comparison was made between the proposed model and an existing model neglecting the momentum conservation principle at the junction, with the former showing better prediction of the peak water levels near the confluence. Numerical experiments were conducted to analyze the influences of reservoir operation and discharge capacity of the dam on flood routing and bed evolution in the river network. It is demonstrated that decreasing pool level during flood season and increasing discharge capacity are both valid measures to alleviate sedimentation in the Sanmenxia Reservoir, and the former measure is a prerequisite. Therefore, the model presented here can help to enhance the understanding of river network system subject to high sediment input and inspire better strategies on sustainable reservoir management.

从龙门到三门峡大坝的黄河中段，由于沿河水道的几何形状突然变化以及洪水和底泥的水量变化较大，因此难以预测高浓度洪水过程。河流和支流。提出了一种基于Godunov型FVM方案的河网模型，以研究高浓度洪水期间的水流动力学，泥沙输送和河床演变。采用准二维算法来计算结点单元处的速度，然后将其用于提供内部边界条件。可以同时执行每个范围的计算，并且可以使用OpenMP并行化解过程。与串行程序相比，加速因子在理论上随着河网的到达数量线性增加。模拟了两个洪水事件，分别具有明显的侵蚀和沉积，以验证该模型。计算出的水位，流量和非均匀悬浮负荷的分数浓度与测量值一致。比较了所提出的模型和忽略交界处动量守恒原理的现有模型，其中前者显示出对汇合处峰值水位的更好预测。进行了数值实验，分析了水库大坝的运行和排洪能力对河网洪水演进和河床演变的影响。结果表明，汛期库水位下降和流量增加是缓解三门峡水库泥沙淤积的有效措施，前者是先决条件。因此，这里提出的模型可以帮助加深对高沉积物输入的河网系统的理解，并激发出更好的可持续水库管理策略。