EVOLUTION FEATURES AND WAY OF THINKING FOR REGIME CONTROL AND REGULATION OF THE YANGTZE ESTUARY

The article summarizes the historic and recent evolution features of the Yangtze estuary. Recently, deposition accelerated and the water diversion ratio decreased gradually in the North Branch, while the water diversion ratio increased and the change in scouring and deposition becomes stronger in the river channel at local sections in the South Branch. Such evolution situation severely constrains the sustainable development of the riparian economy, so control of the river regime is vitally important. The basic principle for regime control is to strengthen the role of control of the nodes and bifurcate mouths to the river regime based on the evolution features of the estuary and the principal aspects of the influence factors to the channel evolution and determine different regime control objectives in the light of the difference of various river sections. The main way of thinking for regime control is to control the direction of primary current at the Xuliujing node and stabilize the Baimao Shoal to create favorable conditions for the river regime of the downstream channel and the North Branch; narrow the middle and lower North Branch, reduce the tidal flow, adjust the power ratio of river flow and tidal current, and alleviate the backflow of water, and sediment to the South Branch; and harness the Three Shoals and stabilize the river regime to provide favorable conditions for the riparian infrastructures and the deep water navigation course of the North Pass of the South Sub-branch.