Sedimentation Styles Of Dike Type Estuary Channel And Siltation In The Yangtze Estuary Deepwater Navigation Channel

Estuarine area is the interface of river and sea. With the advantages of rich resources and convenient transportation, this area has become an economic and cultural developed zone and plays an important role in the regional development. Drastically affected by river basin and coastal human activities, the coastal environment of estuary are facing drastic changes and a series of problems such as channel siltation, restricting the estuarial region's economic development. Due to the artificial regulation project of dikes and groins, the dike type estuary is gradually formed.In order to study the sedimentation problems of such estuary and channel, five aspects including river reach broadening, tide and runoff jacking, unsmooth river regime, local circulation flow and density current plunging, which have influence on dike type estuary sedimentation, are discussed in this paper:(1)the river reach broadening deposition way, which means the broadening of the river reach leads to the decrease of the flow velocity and the sediment carrying capacity;(2)the tide and runoff jacking deposition way, which means the stagnation flow area caused by the interaction between tide and runoff leads to the sediment deposition;(3)the unsmooth river regime deposition way, which means the big angle between the flow centerline by dikes and groins and hydrodynamic axis leads to the flow resistance and sediment deposition;(4)the local circulation flow deposition way, which means the estuary groin engineering leads to the local vortex that brings the sediment in groins into the channel under the drive of tidal flow;(5)the density current plunging deposition way, which means sediment in the groin field plunges into the channel in the form of density current and causes deposition.Then under the background of major rivers in China, mathematical models of the conceptual estuary and channel are established. Through simulation of flow field, the sedimentation ways are analyzed. Last, the numerical model of the Yangtze Estuary Deepwater Navigation Channel is established and its tidal level, flow velocity and direction of the model are verified with the observed data. Corresponding to the five kinds of deposition ways of dike type estuary, the possible reasons for sedimentation in the Deepwater Navigation Channel are analyzed.