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黄河下游滩地是蓄滞洪水的主要场所 ,滩区边界条件的变化对滩区水动力条件和阻力特性产生了较大影响。通过系统分析漫滩洪水期典型滩区实测资料表明 ,近年来滩区阻水建筑物增多 ,局部水头损失增大 ,水动力作用明显减弱 ,滩区水面比降仅为大河比降的 1/3～ 1/2 ;同时 ,滩区面积增大 ,植被增加 ,滩地阻力也增大。若直接采用大河比降反求滩区糙率系数 ,结果比实际糙率偏大很多。因此在用水文学和水动力学数学模型进行黄河下游排洪能力计算过程中 ,应注意滩区比降与糙率的率定及匹配
The beach land in the lower reaches of the Yellow River is the main site for flood storage and storage. The changes in the boundary conditions of the beach area have a significant impact on the hydrodynamic conditions and the resistance characteristics of the beach area. Through the systematic analysis of the data of typical floodplain floodplain period, the water blocking structures in the floodplain in recent years have been increased, the local head loss increased, and the hydrodynamic effect has been obviously weakened. The surface water ratio of the floodplain is only 1/3 of that of the large river ~ 1/2; the same time, the beach area increased, vegetation increased, beach resistance also increased. If directly using large river ratio to reverse beach roughness coefficient, the result is much larger than the actual rough rate. Therefore, in hydrology and hydrodynamics mathematical model for the calculation of discharge capacity of the lower Yellow River, we should pay attention to the rate of beach area ratio and roughness rate and matching