| 黄河下游不同河段分组悬沙输移对河床冲淤的影响 |
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| 引用本文： | 程亦菲,夏军强,周美蓉,邓珊珊.黄河下游不同河段分组悬沙输移对河床冲淤的影响[J].水科学进展,2022,33(3):506-517. |
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| 作者姓名： | 程亦菲 夏军强 周美蓉 邓珊珊 |
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| 作者单位： | 武汉大学水资源与水电工程科学国家重点实验室, 湖北 武汉 430072 |
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| 基金项目： | 国家自然科学基金资助项目51725902国家自然科学基金资助项目51579186 |
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| 摘 要： | 小浪底水库运行后, 坝下游分组悬沙输移特点发生改变, 不同河段冲淤过程有所差别。基于1999—2018年坝下游实测水沙资料及固定淤积断面地形数据, 分析汛期分组悬沙输移的沿程调整特点, 建立分组悬沙输移及河床边界条件双重影响下不同河段河床累计冲淤量的计算关系。分析结果表明: ①汛期各组沙输沙率远小于蓄水前, 且中沙输沙率降幅最大, 在各水文断面平均降幅为85%;沿程上细沙输沙率基本不恢复, 而中沙和粗沙恢复距离分别到利津及艾山。②坝下游河床持续冲刷, 各河段河床组成均发生不同程度的粗化; 在拦沙后期(2007—2018年), 游荡段和过渡段床沙中细沙和中沙占比不足5%, 对悬沙几乎无补给作用, 而弯曲段床沙对中沙仍有一定的补给能力。③下游各河段以冲刷下切为主, 但调整幅度不同, 故对水流的约束能力有所差异。建立了各河段累计冲淤量与前期河相系数及进口断面分组来沙系数的经验关系, 并采用2019年下游水沙数据对公式进行了初步验证, 公式能合理反映断面形态与分组悬沙输移对河床累计冲淤过程的影响。
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| 关 键 词： | 分组悬沙 不平衡输移 床沙补给 河床冲淤 黄河下游 |
| 收稿时间： | 2021-06-28 |
Effects of grouped suspended sediment transport on channel evolution in the Lower Yellow River |
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| Affiliation: | State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China |
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| Abstract: | The operation of the Xiaolangdi Reservoir greatly changed the transport process of grouped suspended sediment in the Lower Yellow River (LYR), accompanied with the discrepancy in channel evolution of different reaches. Based on the measured hydrological data from 1999 to 2018, the transport characteristics of different grouped suspended sediment during flood seasons have been analyzed, and moreover an empirical function for calculating the cumulative channel evolution volume of each reach has been established. Results show that: ① Sediment discharge of each grain-size dramatically decreased after the reservoir operation, among which the sediment discharge of medium grain-size decreased most by 85%;from the spatial perspective, the sediment discharge of fine grain-size seldom increased along the channel, while that of medium and coarse grain-sizes increased to the stations of Lijin and Aishan respectively. ② The riverbed in the lower reaches became more coarsely grained owing to the continuous channel degradation, which resulted in the inadequate supply of fine and medium grain-size sediments to the suspended sediment in the braided and transitional reaches. While the mildly coarsened riverbed in the meandering reach could still supply the medium grain-size sediment to the suspended load. ③ Channel undercutting generally occurred in the LYR, accompanied by different channel adjustment characteristics in these reaches, which resultantly exerted different effects on the flow condition. A close correlation has been found between cumulative channel erosion and post-flood geomorphic coefficient in the last year and incoming sediment coefficients of the specified grain-sizes during flood seasons, which can reasonably account for the effects of channel boundary condition and non-equilibrium transport of grouped suspended sediment. Additionally, the verification process of the proposed empirical equation shows that the calculated values agreed with the measured channel evolution process. |
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