Abstract Since the construction of the Deepwater Navigation Channel Project in Yangtze River Estuary 1998, it is extremely imperative to clarify the sediment dynamics in Yangtze River Estuary to reduce deposition risks in the channel. However, the sediment deposition mechanism has not been well understood. Therefore, four mechanisms of sediment deposition in Yangtze River Estuary were simulated and another one was analyzed through discussion in this research. First, a two-dimensional mathematical model of Yangtze River Estuary and four conceptual estuary models were established. Through the comparison of the models in the flow field and the sediment deposition, the characteristics of each mechanism were analyzed. The results indicated that the flow expansion, residual currents, riverbed thalweg orientation and local circulation played important roles respectively in different areas of the Yangtze River Estuary. Specifically, in the river mouth, the sediment deposition is mainly considered related to the flow expansion. While, in zones where riverine discharge and tide meet, the residual current is the primary cause. In the South Branch and the North Channel with interlaced shoals, the riverbed thalweg orientation is the major factor of the channel deposition. In the Deepwater Navigation Channel of the North Passage, the local circulation is the main cause. Finally, the sediment density current was discussed and concluded to be one of the causes leading to the sediment deposition in the North Passage. It was clear that the conceptual estuary models can be applied in explaining the mechanisms of the sediment deposition qualitatively.

中文翻译：

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长江口泥沙沉积数值分析——从河口概念模型看

摘要 长江口深水航道自1998年开工建设以来，明确长江口泥沙动态，降低航道淤积风险迫在眉睫。然而，沉积物沉积机制尚未得到很好的理解。因此，本研究通过对长江口沉积物沉积的四种机制进行了模拟，并对另一种机制进行了讨论。首先，建立了长江口二维数学模型和四个河口概念模型。通过流场模型与沉积物沉积模型的对比，分析了各机理的特点。结果表明，流动膨胀、剩余电流、在长江口不同区域，河床浅层定向和局部环流分别发挥了重要作用。具体而言，在河口，主要考虑泥沙淤积与水流扩张有关。而在河流流量和潮汐交汇的地区，剩余电流是主要原因。在具有交错浅滩的南支和北航道中，河床浅层取向是航道沉积的主要因素。在北航道深水航道，局部环流是主因。最后讨论了沉积物密度流是导致北航道沉积物沉积的原因之一。