黄河下游游荡段非均匀悬沙输移特点

黄河下游水流含沙量大，河床调整迅速，河道输沙能力变幅大，输沙过程与规律复杂。因此研究黄河下游泥沙输移规律，是研究河床变形过程、预测河道发展趋势的基础，对水沙治理与河道整治规划具有重要的现实意义。本文以黄河下游游荡段为对象，基于1986—2015年游荡段实测水沙资料与地形资料，分析了花园口-夹河滩河段与夹河滩-高村河段的非均匀沙输移特点。研究结果表明：①输沙率经验公式的相关性与泥沙粒径有关，泥沙粒径越小，输沙率经验公式的相关性越好，细沙的相关系数可达0.99。②排沙比与来沙系数、河相系数均呈负相关，且河相系数较大时，排沙比变幅较小。夹河滩-高村河段的中沙排沙比与来沙系数、河相系数的相关关系较其他粒径组泥沙更为密切，花园口-夹河滩河段则分别为细沙和粗沙排沙比。③在同时考虑了水沙条件与断面形态对河段排沙比的影响之后，输沙率经验公式的精度明显提高，相关系数在0.48 ~ 0.65之间。

Characteristics of non-uniform sediment transport in braided reach of the Lower Yellow River

The Lower Yellow River(LYR)is featured with complicated processes and trends of sediment transport due to its high sediment concentration and rapid channel adjustment.Its sediment transport characteristics are an essential factor for flow-sediment control and river planning.This study examines non-uniform sediment transport in the Huayuankou-Jiahetan reach(HJR)and Jiahetan-Gaocun reach(JGR)based on the 1986-2015 survey data of flow,sediment,and cross-sectional profiles,achieving the following results.(i)For fine sediment,an empirical formula of its transport rate manifests an excellent correlation coefficient of 0.99.(ii)The sediment discharge ratio(SDR)is negatively correlated with both the sediment coefficient of incoming flow and hydraulic geometry,but its variation becomes very mild when the latter factor is increased up to a rather large value(30 m^-1/2).In JGR,the SDR of mediumgrained sediment is more correlated to these two factors than fine or course sediment,while in HJR,the SDR of its fine sediment and coarse sediment more correlated.(iii)When the influences of both the flow and sediment conditions and the channel geometry are considered,all the empirical formulae are improved greatly,offering much better prediction accuracy and higher correlation coefficients in the range of 0.48-0.65.