## 1 Introduction  
Rivers, as highly dynamic constituents of the Earth's hydrological cycle, possess intrinsic economic and ecological value, playing a crucial role in the advancement of human societies [1], ecosystem sustainability [2], and regional climate [3]. Yet, their natural balance has been threatened by a wide range of anthropogenic stressors such as the construction of dams, which now number in the tens of thousands globally, and this number is growing [4]. Dams are often engineered to generate hydropower and alleviate flooding events [5, 6]; however, they concurrently interrupt riverine continuity and engender considerable spatiotemporal modifications in fluvial flow and sedimentary patterns [7, 8, 9]. Such drastically changed flow-sediment regimes subsequent to dam development have precipitated significant downstream consequences, encompassing geomorphological, ecological, and societal domains [10, 11]. The Three Gorges Dam (TGD; 30\({}^{\circ}\)44\({}^{\prime}\)18\({}^{\circ}\)N, 111\({}^{\circ}\)16\({}^{\circ}\)29\({}^{\circ}\)E), the world's most expansive dam, is strategically constructed within the upper reaches of the Yangtze River, which holds the distinction of being Asia's preeminent river (Figure 1). Commencing with the impoundment in 2003, the TGD has exerted considerable influence on the environmental dynamics of the middle and lower reaches of the river (e.g., a sharp reduction of \(\sim\)90% in sediment loads from 1950-2002 to 2003-2020). The Middle Yangtze River (MYR), being the proximate reach downstream of the TGD, has consequently experienced substantial alterations to its riverine ecosystem, primarily attributable to the regulation of flow and sediment regimes. Recent studies suggest that the TGD could exacerbate floods in certain river systems by triggering enhanced vegetation resistance [12]. Changes in bar and vegetation characteristics reflect the dynamics and geometry of rivers and have consequently been studied for the purposes of flood control, water supply, waterway navigation, aquatic ecosystems, and biogeography [13; 14; 15; 16; 17]. Variations in bar and vegetation downstream of dams have been documented in many rivers worldwide, and variation trends are different mainly due to runoff regimes, sediment transport, vegetation colonization, and so on [18; 19]. For example, a marked degradation of bars in the lower Trinity River (USA) following the Livingston Dam construction was corroborated, a phenomenon precipitated by a considerable diminution in sediment load [20]. In addition, the vegetation growth in the Sauce Grande River (Argentina) subsequent to damming has been facilitated by the conservation of base flow levels and the diminution of flood-induced disruptions [21]. Furthermore, the downstream environmental perturbation resulting from the Balbina Dam (Brazil) spans in excess of 100 km, with vegetation experiencing mortality up to two decades following its establishment, attributable to the repercussions of hydropower plants on hydrological regimes [22]. Recently, the morphodynamic evolu  
Figure 1: Sketch map of the study area: the Yangtze River Basin and the Middle Yangtze River with locations of sub-reaches, hydrometric stations, bars, and diversion inlets. tion of large bars in the Yangtze River and their responses to anthropogenic interferences have been investigated [23; 24]. For example, the bar surface area in the Jianli reach exhibited greater dynamism under natural flow (1985-2003) as opposed to the regulated flow (2003-2012) [16]; the sandbars in the Yichang-Chenglingji reach were found to have primarily shrank due to the reduction in suspended sediment concentration following the TGD operation [25]; the river bar erosion and deposition patterns of the Shashi reach transitioned from \"low bar erosion-high bar deposition\" to \"both low and high bar erosion\" since the TGD damming [26; 27].