近期长江口北槽河段河槽演变对人类活动的响应

Multi-beam bathymetric measurements made during November 2014 were used to investigate micromorphology of the North Passage of the Yangtze River estuary. The physical properties of the micromorphology were assessed by grain size analysis of bottom sediment samples collected. The morphological changes of the riverbed channel were assessed by the digitized bathymetric data. Results show that channel erosion occurred in the North Passage from 1979 to 2019 because of human activities. net volume loss and mean annual net volume loss reached 0.36 × 10⁸ m³ and 0.009 × 10⁸m³ yr^-1 in the North Passage. Increase of depth water in the North Passage may aggravate the saltwater intrusion. The sediment supply at Datong Hydrological Gauging Station showed a declining trend because of the influence of the Three Gorge Dam (TGD), which may have contributed to channel erosion of the outer estuary. Channel erosion occurred in main channel and distinct accretion occurred in the northern side and southern side because of the Deepening Waterway Project. In addition to three kinds of common bedforms: smooth surface, gully and dune, there are also two kinds of micromorphology under the human intervention: hollow, low-lying land and dredging mark. The mean length and mean height of dunes in the middle reach is 39.41 and 0.48 m, respectively, and the mean length and mean height of dunes in the lower reach is 11.11 and 0.33 m, respectively. The value of bed roughness (ks) associated with the dunes in the middle reach and lower reach is 0.14 and 0.19, respectively. A small area of dunes in the middle and lower reaches of the North Passage was observed for the first time in the turbidity maximum zone of the Yangtze River Estuary.