PRELIMINARY STUDY OF THE RIVER BED REGULATION IN THE PROCESS OF THE CONSTRUCTION OF THE YANGTZE ESTUARY DEEPWATER CHANNEL PROJECT

摘要

By analyzing the topographical features of the south channel, the bifurcation section, the south passage, and the north passage, and investigates on the riverbed regulation during the course of the construction of the Yangtze Estuary deepwater channel project are presented in this paper. There are large quantities of bed load sediment moving from upstream to the south channel. These bed load sediment is mainly relevant to two flood of Yangtze River taken placed in 1998 and 1999. The sediment in the South channel often goes downstream, and the entry of the South Passage will inevitably be in deposition if scour occurs in the South channel, which indicates that the South Passage is the main access of bed load sediment in the Yangtze Estuary. During the course of the deepwater channel regulation, the ebb flow ration of the North Passage will decrease whereas the ebb flow ration of the South Passage will increase because the regulation structures give rise to the resistance of the flow in the North Passage. And there occurs scour in the entry of the South Passage and deposition in the upper section of the North Passage. The flow momentum in the spur-dike section will increase and the topography will be washed out dramatically after the spur-dike project, which indicate the spur dike begin to play an important role in water diversion, sand retaining and deposition reduction. The topography transform in the lower section of the South Passage depends on the transform in the upper section of the South Passage. The lower section is subjected to deposition if there is a scour in the upper section. The balances of scour and deposition in the spur-dike section and middle section of the North Passage are maintained in May 2001, and the riverbed regulation came to be stable. The flow ration of north passage must be controlled to guarantee that it will not continuously be reduced so severe that the beyond retrieve change will occur between south passage and north passage during the second stage of Yangtze estuary deepwater channel regulation project.