来水来沙与侵蚀基准面对河床演变的协同作用机制

Integrated impacts of flow discharge and sediment load and base level on fluvial processes are significant characteristic of rivers under complex upstream and downstream disturbances. Previous studies generally consider the impact of the upstream or downstream factors on channel evolution separately. The mechanism of the integrated impacts of upstream and downstream conditions on fluvial processes has yet been studied comprehensively. By adopting multiple study methods of data analysis, flume experiment and theoretical study, this project aims to investigate the integrated impacts of water and sediment conditions and base level on fluvial processes in different time scales. Flume experiments with the changes of flow discharge and sediment load and/or base level will be carried out. A general physical mode for the propagation and superposition of progressive and retrogressive erosion and deposition will be proposed. Moreover, based on the delayed response model for the evolution of rivers in non-equilibrium, a calculation method for channel adjustment under the integrated impacts of upstream and downstream conditions will be proposed. The proposed method will be used to simulate the spatial and temporal evolution of the Xiaobeiganliu reach of the Yellow River and lower Wei River, which have been impacted by the operation of Sanmenxia Dam and varying water and sediment conditions, and the lower Yellow River impacted by estuary evolution and flow discharge and sediment load. The impacts of upstream and downstream conditions on channel adjustment will be estimated and compared quantitatively. This project helps to deepen the understanding of the self-adjustment behavior of the fluvial system in different spatial and temporal scales, and provides technical support for river management, dam operation, estuary training and management, etc.

来水来沙与侵蚀基准面对河床演变的协同作用是上、下游复杂扰动下冲积河流自动调整作用的重要特征，但以往研究往往孤立地看待来水来沙和侵蚀基准面对河床演变的影响，缺乏对二者协同作用机制的深入探讨。本项目拟采用资料分析、水槽实验与理论研究相结合的手段，探讨不同时间尺度内上、下游控制因素对河床演变的协同作用；开展来水来沙与侵蚀基准面单独与共同变化的水槽实验，观测沿程与溯源冲淤随时空的传播及叠加过程，提出二者的协同作用模式；采用模拟非平衡态河床演变过程的滞后响应模型，建立考虑上、下游控制因素协同作用机制的河床演变计算方法；选取受三门峡水库运用和水沙条件影响的黄河小北干流和渭河下游，以及受来水来沙和河口影响的黄河下游为典型河段，模拟河床的时空冲淤演变过程，定量计算上、下游扰动对河床演变的影响。研究成果有助于深入认识不同时空尺度下冲积河流的自动调整作用规律，为河流管理、水库运用、河口治理等提供技术参考。

来水来沙与侵蚀基准面对河床演变的协同作用是上、下游复杂扰动下冲积河流自动调整作用的重要特征。本项目采用实测资料分析、水槽实验与理论研究相结合的手段，以黄河口及下游河道、美国图特河北汊为研究对象开展研究。以黄河口及下游河道为主要研究对象，辅助河口河道演变的概化水槽试验，分析河口改道与演变规律，研究黄河口冲淤变化对下游河道演变的影响，建立黄河下游河道侵蚀基准面的计算方法，探讨黄河下游河道在来水来沙与侵蚀基准面共同作用下的冲淤演变规律，并采用河床演变的滞后响应模型，建立了其长时段冲淤计算方法。以美国华盛顿州图特河北汊为研究对象，研究来水来沙急剧变化导致的河床演变的滞后响应规律，引入国际上应用较广的河道演变阶段模型（Stream Evolution Model），分析图特河北汊河道不同演变阶段的时空变化特征，结果表明，河道演变阶段模型适用于图特河的演变过程，反映了研究河段的时空滞后响应规律，揭示了时间和空间尺度上河床演变的联系与时滞关系。研究成果发表在《International Journal of Sediment Research》、《River Research and Application》、《水利学报》、《泥沙研究》等国内外重要期刊。