Aquatic vegetation in rivers influences the flow structure, impacting the sediment transport in the river and further changing the ecosystem and geomorphologic evolution of the river. In this paper, an improved random displacement model (RDM) is proposed to investigate the concentration of suspended sediment (CSS) in flows with flexible submerged vegetation. Considering the effect of sediment resuspension on sediment transport, a probability model of sediment resuspension is embedded into the RDM so that the simulation process is more consistent with the natural cases. For the streamwise development of flow with flexible submerged vegetation, the flow is divided into a flow adjustment region and a fully developed region in the longitudinal direction. The vertical distributions of the flow velocity and turbulence diffusion coefficient were analyzed in these two regions, and they were incorporated into the RDM to simulate the along-flow development of the CSS. The simulated concentrations were compared with the experimental data. The mean relative errors (MREs) were below 15%, the root mean square errors (RMSEs) were below 0.20, and the Nash–Sutcliffe efficiencies (NSEs) ranged from 0.71 to 0.99, indicating that the improved RDM is plausible and reliable. In addition, the along-flow distribution of the sediment transport rate (STR) was analyzed. The rate exhibited a decreasing trend during the flow adjustment region and tended to stabilize during the fully developed region. This study provides a new way of thinking for research on sediment transport in rivers with aquatic vegetation, which is of great significance for achieving the sustainable development of river ecosystems and the optimal design of river channels.

中文翻译：

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淹没植被生态流中悬浮沉积物的迁移和混合建模：基于随机位移模型的分析


河流中的水生植被影响水流结构，影响河流中的沉积物运输，并进一步改变河流的生态系统和地貌演变。本文提出了一种改进的随机位移模型 （RDM） 来研究具有柔性淹没植被的流动中悬浮沉积物 （CSS） 的浓度。考虑到泥沙重悬对泥沙运移的影响，将泥沙重悬的概率模型嵌入到 RDM 中，使模拟过程与自然情况更加一致。对于具有柔性沉没植被的水流的流向发展，将流向分为流量调节区和纵向完全发育区。分析了这两个区域的流速和湍流扩散系数的垂直分布，并将其纳入 RDM 以模拟 CSS 的顺流发展。将模拟浓度与实验数据进行比较。平均相对误差 （MRE） 低于 15%，均方根误差 （RMSE） 低于 0.20，Nash-Sutcliffe 效率 （NSE） 在 0.71 到 0.99 之间，表明改进的 RDM 是合理和可靠的。此外，还分析了沉积物传输速率 （STR） 的沿流分布。速率在流量调整区呈下降趋势，在充分开发区趋于稳定。本研究为水生植被河流泥沙运移研究提供了新的思路，对实现河流生态系统的可持续发展和河道的优化设计具有重要意义。