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By use of bathymetric chart,recent change of the riverbed in the North Passage of the Yangtze Estuary has been studied in this paper.The main channel of the upper,middle and lower(section)in the North Passage has been successively eroded and its groin field significantly deposited.At the same time,sediment has been deposited on the entrance region.Erosion and deposition had responded rapidly to the construction of the regulation engineering.There was about one year duration of lagging between erosion in the deep channel and the construction of the regulation engineering.The siltation lag of time in the groin field varied with the initial depth,but the average deposited thickness was about 0.5 m per year.Volumetric analysis demonstrates that there is a increasing trend of siltation in the North Passage after 2002,because of the difference in duration and quantity between erosion in the deep channel and deposition in the groin field.The water volume of the North Passage was reduced by ≈9%(280 million m3)between 2002 and 2006.Sediment budget reveals that the main sediment deposited in the North Passage takes its source from the river and the ocean.The decreasing water volume was attributable to shoaling in the groin field.Its triggering factors for increased sedimentation are the navigational improvements(jetties and groins)after 1998,which altered the passage boundary and destroyed the equilibrium state on the average ebb and flood sediment fluxes.The establishment of a stable estuary is attributed to a reduction in depth of the groin field.The forecast on the sediment deposition quantity and continuous infilling time in the groin system is about 325×106m3 and 6～7 years,respectively.
By use of bathymetric chart, recent change of the riverbed in the North Passage of the Yangtze Estuary has been studied in this paper. The main channel of the upper, middle and lower (section) in the North Passage has been successively eroded and its groin field significantly deposited. At the same time, sediment has been deposited on the entrance region. Erosion and deposition had rapidly rapidly the construction of the regulation engineering. there was about one year duration of lagging between erosion in the deep channel and the construction of the regulation engineering.The siltation lag of time in the groin field varied with the initial depth, but the average deposition thickness was about 0.5 m per year. Volumetric analysis demonstrates that there is a increasing trend of siltation in the North Passage after 2002, because of the difference in duration and quantity between erosion in the deep channel and deposition in the groin field. The water volume of the North Passage was reduced by 9% (280 million m3) between 2002 and 2006. Sediment budget reveals that the main sediment deposited in the North Passage takes its source from the river and the ocean. Where decreasing water volume was attributable to shoaling in the groin field. Its triggering factors for increased sedimentation are the navigational improvements (jetties and groins) after 1998, which altered the passage boundary and destroyed the equilibrium state on the average ebb and flood sediment fluxes. the establishment of a stable estuary is attributed to a reduction in depth of the groin field. forecast on the sediment deposition quantity and continuous infilling time in the groin system is about 325 × 106m3 and 6 ~ 7 years, respectively.