Preliminary study on the role of tidal currents in the filling of the paleo-Changjiang River Estuary

The Changjiang River Delta was formed through the filling of the paleo-Chartgjiang River Estuary(PORE).The study on the role of tide and tidal currents in the filling of the PCRE can help to understand the development of the Changjiang River Delta better. With a 2-D tide model, the MZ tide and tidal currents in the Bohai Sea, Huanghai Sea and East China Sea at the postglacial marine transgression maximum are simulated. Based on the hydrodynamic data obtained, the sediment transport fields of 8 kinds of grain size in the PCRE and its adjoining areas are calculated, and the seabed erosion-accretion pattern is obtained in terms of the divergence of sediment transport rate. The results show that at the post-glacial transgression maximum, there existed a noticeable wave loop of standing tidal waves with the antinode of the wave loop being located in the mouth of the PCRE, and the wave loop lines being protruded towards sea. Under its control, tidal currents converge to or diverge from the mouth of the PORE. Within a single tidal cycle, net sediment was directed towards the PCRE. Thus the PCRE has been filled under the conditions that the Changjiang River supplies a large amount of sediment, and the tide and tidal currents in the open sea impel this sediment to deposit as much as possible in the PCRE. The tide and tidal currents in the open sea provide necessary and favorable dynamic environment for the filling of the PCRE and the development of the Changjiang River Delta.