Abstract: The dominant controlling dynamics for the Changjiang Estuary is the interaction between the strongly periodic tide oscillation and the weakly periodic Changjiang River runoff. The astronomical tide in this region is the combination of the semidiurnal and diurnal tides, which produces the shallow tide wave due to the nonlinear interaction between these tide components. Therefore the tidal asymmetry in one period is subsequently induced. The tide wave mainly flow along the coasts with the northward direction, and turn to the northwestern direction into the North Passage and North Channel. The studied region, Hengsha Shoal, is characterized as the shallow shoals and deep channels, where is the buffering zone for river mouth and open ocean. This complex bathymetry produces the motions of the tide wave and runoff. The current in the channel and north region of Hengsha Shoal has the alternating pattern. And the significant rotating current dominates the south area, which plays an important role on the stability of the local bathymetry and the strong cross-channel current. Since the Changjiang River’s runoff flow eastward, and float on the surface in this region, producing significant two-layer system in the vertical direction.

Key words: tide motion, hydrodynamics, river runoff, alternating current, rotating current, current ellipse, terrain feature, wave, wind