Deltaic channels are key pathways connecting rivers and the ocean, which is of significance for in maintaining estuarine stability and material transport processes between land and sea. However, deltaic channels have experienced dramatic variations in the Anthropocene era, including seriously scouring induced by decline of riverine sediment delivered to the ocean, trenching caused by dredged works and episodic filling by storm events. Here, a series of hydrology, sediment as well as elevation data between 1979 and 2020 of North Passage (NP), one of most important navigated channels over the Changjiang Estuary Delta, were used to analyze its long-term morphodynamic processes. Results show that during 1979–2020, NP capacity presented stage changes: gentle increase stage between 1979 and 1997, fluctuation stage between 1997 and 2002, fast-descend stage between 2002 and 2007, slow growth stage between 2007 and 2020, and periodic signals of 13 and 25 months can be detected in NP volume. Meanwhile, the shoal zone and the deep channel showed long-term decrease and increase trend respectively, making NP turn into a narrow and deep deltaic channel. Moreover, NP exhibited two major morphodynamic patterns. The first mode indicates the long-term continuous erosion of the main-channel region and persistent deposition in the groin region. The second mode explains the transition of the erosion/deposition state of NP, where the huge mouth bar system in NP was shifted seaward accompanied by a decrease of its extent. The periodic changes of fluvial water and sediment may contribute the oscillation of erosion and accretion process of NP. The construction of engineering structures and long-term dredging works resulted in constant deposition in the groin region with continuous erosion in main-channel region. The existence of estuarine turbidity maximum was conductive to deposition in the main-channel region.

中文翻译：

---

大型河流潮汐三角洲疏浚河道的形态动力学


三角洲河道是连接河流和海洋的重要通道，对于维持河口稳定和陆地与海洋之间的物质输送过程具有重要意义。然而，三角洲河道在人类世时期经历了巨大的变化，包括流入海洋的河流沉积物减少引起的严重冲刷、疏浚工程造成的沟渠以及风暴事件造成的间歇性充填。这里，利用长江口三角洲最重要的航道之一北航道（NP）1979年至2020年的一系列水文、沉积物和高程数据来分析其长期形态动力学过程。结果表明，1979—2020年，NP容量呈现阶段性变化：1979—1997年平缓增长阶段、1997—2002年波动阶段、2002—2007年快速下降阶段、2007—2020年缓慢增长阶段、2007—2020年呈现周期性信号。 13个月和25个月可检测到NP量。同时，浅滩带和深水河道分别呈现出长期减少和增加的趋势，使北太平洋变成了窄而深的三角洲河道。此外，NP 表现出两种主要的形态动力学模式。第一种模态表明主河道区域长期持续侵蚀，腹股沟区域持续沉积。第二种模式解释了NP的侵蚀/沉积状态的转变，其中NP的巨大河口坝系统向海移动并伴随着其范围的减小。河流水体和沉积物的周期性变化可能导致纳米粒子侵蚀和增生过程的振荡。 由于工程构筑物的建设和长期的疏浚工程，导致腹股沟地区不断淤积，主河道地区不断受到侵蚀。河口浊度最大值的存在有利于主河道区的沉积。