长江口深水航道治理工程实施后南北槽分汊段河床演变

River-bed evolution in the braided reach of the south and north passage after implementing Yangtze estuary deepwater navigational improvements

利用1998-2006年的水深测图和南北槽分流、分沙比测量资料,研究了长江口深水航道治理工程实施后南、北槽分流比的变化过程、原因及其与分汊口河床冲淤演变的关系。结果表明,随着长江口深水航道治理工程的实施,北槽落潮分流比总体呈减小的趋势,南槽落潮分流比呈增加的趋势。伴随着南、北槽落潮分流比的南增、北减,南槽进口段(长约18 km)的主槽发生了冲刷,北槽进口段(长约12 km)的主槽发生了淤积,南、北槽进口段河槽总过水断面面积呈下降趋势。北槽落潮分流比与北槽河槽总容积、南北槽落潮分流比与各自进口段的河槽断面平均水深之间均具有较好的相关性,据此,预测了未来南、北槽的落潮分流比和进口段河槽冲淤的平衡量值。

By using bathymetric chart and discharged flow data, the relation between the river-bed evolution and change of discharged flow in the braided reach of the south and north passage is studied in this paper. After implementing Yangtze Estuary Deepwater Navigational Improvements, there are an decreasing trend and an increasing trend in the ratio of ebb flow diversion through the north passage and the south passage, respectively. The length of sediment deposited on the entrance region in the north passage is about 12 km long, and that of the eroded on the upper region in the south passage about 18 kin. But the total cross-section area of the entrance reach in the north passage and south passage decreased from 1998 to 2006. There are good correlations between the total channe storage and the yearly averaged ebb flow ratio in the north passage, and the cross-section averaged depth of the entrance reach in the north passage and south passage and their yearly averaged ebb flow ratio, respectively. According to the relationship formula, the change of the ebb flow ratio and the cross-section averaged depth of the entrance reach in the north passage and south passage are evaluated.