Abstract

Sandbank-lagoons are generally natural harbors for their good defense of wave, deep water near the coast and little source of sediments. However, during construction of large-scale deep water harbors, the dynamic environments are changed by constructions such as taking up some waters, digging channels and modifying the mouth shape. Consequently, sediment movement trends and scour or sedimentation distributions in the harbor block need simulating and predicting. Taking Bohe harbor locating on the sandbank-lagoon in South China as the example, water-sediment regime in the harbor block has been studied in this paper, by a two-dimensional mathematical model for suspended sand under comprehensive action of tidal flow with wave. For detail, the calculation format takes the finite differential approach and the solution adopts ADI methods. Numerical simulation of wave and tidal current is realized through adding both item of wave induced radiation stress and combined friction coefficient of wave and current in the control formula. Then coupling with the overall model and localized model is established by the nested grid method. Finally, this model is verified by the measured data. The simulation results show that wave-induced longshore current has a significant impact on the sediment movements in the planned harbor block and its backsilting is controled by SW flow and wave power, and the training dike can trap sediment into the harbor block. And so in the harbor block planned around the west side of Bohe bay mouth not only can shelter the entrance of the lagoon and control wave-induced longshore current, but also improve environment for backsilting.

Keywords: sandbank-lagoon, numerical simulation, wave-induced radiation stress, wave-induced longshore current, harbor block, sediment backsilting