长江口南槽泥沙输移和地貌冲淤机制研究

Estuarine channel is located in a sensitive zone under the hydrodynamic interaction of land and ocean. Its complicated sediment transportation and geomorphological evolution are directly related to the safety of the port engineering and waterways resources. Taking the South Passage of the Changjiang Estuary as an example, sediment transportation character, morphological factor variations and geomorphological evolution processes along the channel are expounded by analyzing the historical records on hydrology, sediment and geomorphology as well as additional observation data and interpreting remote sensing images. Thereafter, Delft3D numerical model is adopted to simulate the water and sediment variations in the South Passage, which can be further used to study the channel water and sediment distribution patterns, to identify the driving mechanism of the sediment transportation and to clarify the coupling relationship between the erosion/deposition of the topography and sediment transportation variation. Furtherly, the process-based analytical model that coupling the dynamic-sediment-geomorphological evolution of the South Passage is established. Through the model, the hydrodynamic mechanism that dominate the channel geomorphological variation can be revealed and the tendency of the channel geomorphology can be predicted. The expected results can enrich the estuary theory system and provide some scientific supports for the channel and port engineering construction.

河口河槽地处陆海动力交互的敏感地带，其复杂的泥沙输移和地貌冲淤直接关乎港工建筑与水运资源的安全运行。本项申请拟以长江口主要入海水道南槽为研究对象，通过对区域历史水、沙及地貌资料和补充强化观测数据等的统计分析，辅之以遥感影像解译，阐明河槽泥沙输移特征、形态要素变化和地貌冲淤过程；然后构建适用于南槽水沙变化的Delft3D数值模型，由此深入研究河槽水沙时空格局，进而甄别影响南槽泥沙输移的驱动机制，弄清河床冲淤和泥沙输移变化的耦合关系；最终提出基于过程的动力-泥沙-河槽地貌演变的解析模型，揭示河槽地貌变化的动力机制，以预测河槽地貌的发展趋势。预期研究成果可丰富河口学理论体系，为长江出海航槽及沿岸港工建设提供部分科学支撑。

河口河槽地处陆海动力交互的敏感地带，是三角洲形成与演变的重要标志，有力地支撑全球河口大型城市社会与经济的发展。本项目以长江口主要入海水道南槽及周边区域为研究区，基于历史水、沙及地貌资料和原型观测数据，将统计技术和数值模拟结合，阐明河槽泥沙输移特征和地貌冲淤过程；甄别影响南槽泥沙输移的驱动机制；最终揭示河槽地貌变化的动力机制。主要结果包括：1）探析长江流域感潮河段动力沉积过程，深化对入海水沙来源的认知。发现感潮河段流量收支显著改变长江入海流量且淤积中心上移100公里，这将对河口动力地貌产生显著影响；2）探索河口地貌对气候变化及人类活动的响应，发现长江口拦门沙动力沉积地貌演变受波浪作用明显，具有“夏季储沙，冬季侵蚀”的季节性特征；极端洪水可冲刷整个河口河槽，进而使其地貌彻底改变；河口区域滩槽系统动力演化亦显著响应于极端洪水事件；3）探明长江口南槽在径潮流动力作用下的泥沙输移和地貌冲淤特征，发现槽内拦门沙演化过程可分为五个阶段，即成长期（1959-1979年）；局部调整期（1999-2003年）；稳定期（2004-2010年）；局部调整期（2011-2017年），并在2018年最终演化为稳定期；4）揭示南槽边滩滩涂地貌形态尺度不变性及地貌行为转换。发现南槽边滩系统通过自我调节向平衡态回归；尽管边滩区域潮流结构与沉积模式基本稳定，但其地貌行为经历明显的状态转换。研究成果丰富了河口学理论体系，为长江出海航槽及沿岸港工建设提供了部分科学支撑，对自然及人类活动影响下河口河槽可持续管理有重要意义。