水库下游河道泥沙沿程恢复特征及恢复饱和系数理论研究进展

[Objective] After the construction of reservoirs, the sediment concentration in discharge flow has significantly decreased. The along-reach recovery of sediment leads to scour adjustments in the downstream river, potentially impacts downstream flood control, water resource utilization, and aquatic ecological environments. Meanwhile, this topic remains one of the key challenges in river sediment dynamics. [Methods] This paper summarizes the existing research results in the characteristics of sediment recovery and theoretical research, analyzes the deficiencies in the current research, and preliminarily discusses the future research directions. [Results] (1) The sediment recovery processes and patterns in the downstream reaches of different reservoirs show significant differences.The recovery varies among different grain-size groups of sediment.Factors such as riverbed composition, inflow of water and sediment from lakes and tributaries all have an impact on the recovery rates of different grain-size groups of sediment. However, there is no consensus on whether there is an exchange between coarse and fine sediment during the along-reach recovery process. (2) Scholars derive the sediment recovery saturation coefficient through back-calculation based on measured data or constructed empirical formulas. The calculation results show a high degree of consistency with actual data. However, due to the differences in measured data, the applicable scope of the empirical formulas is limited. There is not yet a unified understanding on its physical meaning, calculation formulations, and value selection. Among them, some parameters in the expression derived by Han Qiwei are relatively complex, and some key parameters still rely on empirical formulas or empirical values, which to a certain extent restricts its wide application in mathematical models. (3) Abundant achievements have been made in key influencing factors of the sediment recovery saturation coefficient.Theoretical formulas and improved formulas for the vertical distribution of equilibrium sediment transport concentration. Basically meet the current requirements of calculation accuracy. The main difficulty of the research lies in the vertical distribution of sediment concentration under the unsaturated flow condition. Although scholars such as Han Qiwei have proposed effective methods, the calculation and value selection of some key parameters, such as the unsaturated coefficient c, the weight coefficient μ, and the bottom sediment concentration S b, have not yet been well resolved.[Conclusion] Future research can be advanced in the following aspects: 1) strengthen prototype observations, particularly targeted observations of the vertical distribution of sediment concentration, and utilize advanced technologies such as artificial intelligence to integrate and analyze observational data; 2) use advanced and precise measuring instruments to conduct in-depth flume experiments, provide accurate, comprehensive and systematic observational data for theoretical research;3) combine the analysis of measured data and the results of flume experiments for research on the basic theory of along-reach sediment recovery,and deepen research on directions such as the vertical distribution of sediment concentration in unsaturated flows.