Hydraulic Geometry and Theory of Equilibrium Water Depth of Branching River

Based on the flow continuity formula, resistance formula, sediment transport capacity formula and width-depth ratio relationship, the hydraulic geometry relationship and theory of equilibrium water depth for a branching river are established and are suitable for arbitrary section shape. The ratio of cross-sectional area of a distributary channel and the main stream is a power function of its bifurcation ratio with an exponent of 6/7. This was applied to a 12.5 m deep-water channel of the Yangtze River (the North Passage, Fujiangsha Waterway and Shiyezhou Waterway). The reliability of the equilibrium water depth was verified and the construction effect of the channel regulation project was predicted. The results show that the regulation project has achieved certain results on the whole, but some waterways still cannot meet the requirement of 12.5 m navigation depth. It is necessary to adjust the layout of the regulation project and focus on increasing the bifurcation ratio and reducing the flow resistance so as to increase the maximum equilibrium water depth.