Abstract: 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 medium-grained 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.

Key words: non-uniform suspended sediment, sediment transport rate, sediment discharge ratio (SDR), braided reach, the Lower Yellow River (LYR)