Numerous river deltas have been extremely altered by anthropic activities, where a regime shift from net accretion into net erosion may have occurred. In this study, subtidal morphodynamic variations in the Yangtze Estuary (YE) are elaborately analyzed for their causes using high resolution DEM data from bathymetric surveys conducted every two years from 2007 to 2019, and sediment budgetary balance in this highly altered estuary is updated accordingly with mean annual depositional/erosional sediment amounts. The results show that subtidal channel erosion has occurred almost over the whole YE with a mean annual erosion rate of −5.59 cm/yr during the study period. Peak erosion occurred both in the South Branch and the delta front with mean annual erosion rates of −12.64 cm/yr and − 8.11 cm/yr, respectively. The erosion lessened toward the middle estuary where sandy shoals prevail, and a net accretion rate of 3.13 cm/yr was solely measured at the Chongming shoal. Negative correlation between estuarine erosion volume and riverine sediment discharge demonstrates the great impact of upstream hydro-engineering projects on estuarine morphodynamic change, but large-scale estuarine engineering projects also exert remarkable influence on local morphodynamics. Annually eroded sediment amount were estimated as 166 Mt./yr and 206 Mt./yr in the distributary channels and the delta front during the period 2007–2019, respectively, and the former was almost offset by recent sand mining amount of 143 Mt./yr from the distributary channels for land reclamation. Moreover, contemporary eroded sediment mass and sand mining amount from the tidal river reach between Datong and Xuliujing were reckoned as 77 Mt./yr and 44 Mt./yr, respectively. In comparison, recently 124 Mt./yr and 153 Mt./yr of sediment discharge into the tidal river reach at Datong station and the YE at Xuliujing station account for merely 27.5% and 37.7% of their corresponding values before the 1990s, respectively. Annual sediment amount bypassing the estuary into the open sea has decreased by 37.8% from pre-1990s 370 Mt./yr to recent 140 Mt./yr, leading to recently severe erosion in the delta front. It is therefore highlighted that the estuarine system in response to natural and anthropogenic pressures is very dynamic, and the impacts of various engineering projects in the source-to-sink system should be fully taken into consideration when predicting its morphodynamic response in the estuary.

许多河流三角洲已被人类活动极大地改变，其中可能发生了从净增加到净侵蚀的制度转变。在这项研究中，利用 2007 年至 2019 年每两年一次的测深 DEM 数据，详细分析了长江口 (YE) 潮下带形态动力学变化的原因，并相应地更新了这个高度改变的河口的沉积物预算平衡年平均沉积/侵蚀沉积量。结果表明，潮下水道侵蚀几乎发生在整个YE，研究期间年平均侵蚀率为-5.59 cm/yr。南支和三角洲前沿均出现侵蚀峰值，年平均侵蚀速率分别为 -12.64 厘米/年和 - 8.11 厘米/年。中河口以沙质浅滩为主，侵蚀减弱，仅在崇明浅滩测得的净增加率为3.13 cm/yr。河口侵蚀量与河流泥沙排放量呈负相关，表明上游水利工程对河口地貌动力变化影响较大，但大型河口工程对当地地貌动力变化也有显着影响。2007-2019 年间，分流河道和三角洲前缘的年侵蚀泥沙量估计分别为 166 Mt./yr 和 206 Mt./yr，前者几乎被近期 143 Mt 的采砂量所抵消。 /yr 来自开垦分流渠道。而且，大同和徐六井之间潮汐河段的当代侵蚀泥沙量和采砂量分别为77 Mt./yr和44 Mt./yr。相比之下，大同站和徐流泾站河段最近排入潮汐河段的泥沙分别为124 Mt./yr和153 Mt./yr，分别仅占1990年代前相应值的27.5%和37.7%。绕过河口进入公海的年泥沙量从 1990 年代之前的 370 Mt./yr 下降到最近的 140 Mt./yr，减少了 37.8%，导致最近三角洲前缘遭受严重侵蚀。因此要强调的是，河口系统对自然和人为压力的反应是非常动态的，