黄河内蒙古河段河道演变及水力几何形态研究

Study on channel evolution and hydraulic geometry in the Inner Mongolia reach of the Yellow River

黄河内蒙古河段的凌汛年年发生,多次引起河道决口导致洪水灾害。为了提供有效的防洪措施,选取不同河型段中的代表性河道断面,来研究其河道演变特征及其主要影响因素,并从水力几何形态关系上剖析其内在驱动因子。结果表明,河岸组成物质的极大不同决定了各个断面的演变特性及其所在河段的河型差别。以基岩河岸为主的磴口河段的河道最为稳定;以泥质河岸为特征的头道拐断面所在的顺直河段次之;以泥质砂质二元河岸结构为主的三湖河口断面所在的弯曲河流段很不稳定;而以砂质河岸为主的巴彦高勒断面所在的辫状河段最不稳定。河道的演变势必引起其水力几何形态关系的调整,在黄河内蒙古河段,随着流量的变化其水力几何形态的调整主要是通过影响水深和流速来实现的。巴彦高勒断面是上述调整中表现最明显的断面,因此,它所在的河段也是容易决口的河段。三湖河口所在河段的一系列凹岸的强烈冲刷引起河道大幅度摆动,从而也是河道决口的潜在河段。黄河内蒙古河段的河流治理的侧重点应该针对巴彦高勒断面所在的辫状河段和三湖河口断面所在的弯曲河段。对辫状河段要加强整个河段的河岸防护,对弯曲河段以工程防护手段侧重遏制其凹岸的坍塌后退。

The ice flood occurred in the Inner Mongolia reach of the Yellow River yearly and has brought channel breach frequently which resulted in flood disasters.To provide some effective flood control measures,four representative crosssections（Dengkou,Bayangaole,Sanhuhekou and Toudaoguai） which are located in different channel pattern reaches were selected to research the characteristics of channel evolution and its influencing factors,and analyze its driving forces from the view of hydraulic geometry.The results showed that the huge difference of sediment component of river banks determined the evolution traits of the different cross-sections and the distinctions among the different river reaches.The channel of Dengkou reach,mainly formed by bedrock banks,is in the most stable level.The channel of the straight reach（the Toudaoguai located） with muddy banks is stable.The meandering reach,in which Sanhuhekou located,with upper muddy and lower sandy stratum in banks is considerably unstable.The braided reach（Bayangaole located） with sandy banks is also unstable.Any channel evolutions will inevitably lead their hydraulic geometry to adjust accordingly,with the discharge change.The adjustments of hydraulic geometry in the Inner Mongolia reach were conducted by influencing water depth and flow velocity.The Bayangaole cross-section was the most obvious one in the process of adjustment among the four cross-sections,so the reach it located was the most vulnerable one to flood disasters.The channel of the reach Sanhuhekou located experienced evident migration especially along concave bank,so it was also a dangerous reach to potential flood disasters.Considering the analysis mentioned above,some conclusions were put forward as below： the river management should be paid more attention to the braided and meandering reaches.River bank protection should be stressed to the whole braided reaches,and collapse prevention to the concave banks of the meandering reach using engineering means.