Abstract:  

Bedforms were observed in February 2015 with the acoustic multibeam bathymetric. Chart data and surface sediment samples were collected. Based on these data, the recent morphological changes and microtopography features in the Hengsha Passage of the Yangtze River Estuary were studied in this paper. The correlation between the morphological changes and microtopography in the Hengsha Passage was explored in this paper, and the response of the morphological changes and bedforms of the channel beds to the human activities was also explored. Results showed the channel of Hengsha Passage experienced significant erosion because the construction of Three Gorge Dam, the Qingcaosha Reservoir project and the Deepening Waterway Project may have indirectly affected the morphology of the Hengsha Passage. From 2002 to 2013, net volume loss and average annual net volume loss reached 0.86 × 108 m3 and 0.08 × 108 m3 yr-1 in the Hengsha Passage, respectively. A large amount of the eroded sediment from the south entrance of the Hengsha Passage was trapped, resulting in substantial accretion in the Yuanyuansha Waterway and the upper reach of the North Passage. In addition to smooth bed floors, there were erosive microtopography in the Hengsha Passage, such as hollow and scour mark etc.. Due to the channel experienced erosion will lead to enhanced of bed load movement, which can promote the development of dunes. Consequently, there was a large area of dunes developed in the Hengsha Passage.