黄河下游河型转换及弯曲变化机理

Theory of river pattern transformation and change of channel sinuosity ratio in Lower Yellow River

冲积河流河型转换及弯曲变化机理是一个有争议的自然科学难题,根据河道卫星图片量测结果,分析了黄河下游各河段的主河槽弯曲系数变化,各河段的主河槽弯曲系数对比表明,小浪底水库运用后,黄河下游各河段的主河槽弯曲系数有所增大,其中游荡型河段主河槽弯曲系数由1.12增大到1.29,游荡型有向弯曲型转化的趋势;过渡性河段的主河槽弯曲系数由1.23增大到1.35,过渡性河段基本转变为弯曲型;弯曲型河段的主河槽弯曲系数由1.19增大到1.25。探讨了河道形态弯曲变化的机理,从理论上解释了水库的滞洪沉沙作用使下泄水流含沙量减小、泥沙粒径变细、洪峰调平,使下游游荡型有向弯曲型转化的趋势,主河槽弯曲系数增大。

The theory of river pattern transformation and change of sinuosity ratio of alluvial channels is a diffi- cult problem disputed in physical science. Based on the results of satellite images, the change of sinuosity ratio of the main channel of each reach in the Lower Yellow River is analysed. The results indicate that the sinuosity ratio is increasing after the Xiaolangdi reservoir was operated. The braided pattern tends to be trans- formed to meandering pattern for its sinuosity ratio increased from 1.12 to 1.29, the transitional pattern has been transformed to meandering pattern for its sinuosity ratio increased from 1.23 to 1.35, and the sinuosity ratio of meandering reach is increased from 1.19 to 1.25. The theory explains theoretically pattern transforma- tion and change in sinuosity ratio of river channel for sediment concentration decreased, grain size attenuated, and flood peak reduced due to the flood detention and sediment siltation in the reservoir.