Abstract: The hydraulic characteristics of bifurcated channel under bankfull discharge have great impact on the sediment deposition and erosion, the diversion ratio and sediment distribution ratio, as well as the transport of pollutants. In this research, generalized fixed-bed experiment was performed on Daijiazhou segment of the middle stream of Yangtze River as a case study. The variations in hydrodynamic characteristics along curved bifurcated channel under different characteristic flows were analyzed, and the abrupt changes of hydraulic characteristics in different regions of the bifurcated channel under bankfull discharge were examined as well. Results implied that in flow diversion region, the longitudinal slope gradient increased under small discharge, while declined under big discharge; and vice versa in the convex bank; but in concave bank, the longitudinal slope gradient increased along the flow direction. In the adjacent of bankfull discharge, the longitudinal slope gradient in flow diversion region experienced a maximum value, whereas the amplitude of slope gradient undergone a minimum value. In addition, the locations of mainstream line and maximum bed shear stress transferred from the concave bank to the convex bank.

Key words: curved bifurcated channel, bankfull discharge, hydraulic characteristics, abrupt changes, middle reach of Yangtze River, Daijiazhou reach