For the purpose of revealing the mechanism of morphological evolution in the branching estuary which is a prominent type of tidal estuaries and reducing siltation in the Yangtze Estuary deepwater channel, a new relation for the hydraulic geometry of branching estuary was developed by solving the 2D continuity equation in integral form, 2D resistance equation, dimensionless width-depth ratio relation and time-dependent sediment transport capacity formula. The ratio of mean depths of a distributary channel and the main stream is a power function of its bifurcation ratio with an exponent of 2/7. The maximum equilibrium depth at the top of mouth bar in the Yangtze Estuary was calculated as 6.91 m by the proposed hydraulic geometry relation. The result agrees well with the depth acquired from long-term measurement data, which proves the reasonability of the new relation. Furthermore, the hydraulic geometry relation was modified to consider the effect of the groins built in the North Passage by introducing the concept of main channel discharge proportion. The maximum equilibrium depth of the North Passage after the three stages of deepwater channel regulation project was hereby calculated as 8.40, 8.91 and 9.92 m. This lays a theoretical foundation for developing strategies to regulate the Yangtze estuary.
SUN Zhi-lin, YANG Zhong-tao, GAO Yun, XU Dan, HU Shi-xiang. Hydraulic geometry of branching channels in Yangtze estuary. JOURNAL OF ZHEJIANG UNIVERSITY (ENGINEERING SCIENCE), 2014, 48(12): 2266-2270.
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