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In response to recent adjustments in the fluvial shoal~channel pattern of the Tongzhou Shoal Reach in the lower Yangtze River caused by upstream reservoir operations and natural evolution, which threaten the stability of the 12.5-m deep-draft channel, this study investigates the characteristics of recent river regime evolution and the corresponding channel response mechanisms based on measured hydrological, sediment, and topographic data from 2018 to 2024. Spatiotemporal comparison, cross-section analysis, and erosion-deposition calculation were employed. The shoal-channel adjustments in the reach are pronounced and exhibit systematic spatial differences. The annual swing amplitude of the thalweg in Nantong Waterway reaches 0.4 km, and its navigation-obstructing shoal undergoes a three-stage dynamic evolution of "downstream incision-disconnection-aggregation," characterized by channel erosion and bar deposition, together with seasonal patterns of flood-season deposition and dry-season erosion. In contrast, the Tongzhou Shoal Waterway is mainly characterized by continuous retreat along the right margin of Xinkaisha and the development of chutes, which drive the entire Kuzigangsha to migrate southeastward and squeeze the navigation channel. The study further quantifies the key regulatory role of hydrodynamic forcing. During high-flow years, enhanced hydrodynamics induce approximately 30% reduction in the shoal area in the Nantong Waterway, improving channel conditions, but simultaneously intensify chute development and sandbody migration in the Tongzhou Shoal Waterway. During low-flow years, shoal deposition intrude into the navigation channel, deteriorating channel conditions, while the Tongzhou Shoal Waterway exhibits localized adjustments. These findings provide critical scientific basis for predicting the evolution of deep-draft channels and for optimizing the design of dredging and regulation projects, thereby establishing an important theoretical foundation for the long-term stability and sustainable management of the channel.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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