Study of WaveCurrent Coupled Hydrodynamic Responses to a Beach Nourishment Project at Longfengtou Beach

Abstract:

A 2D wavecurrent coupled model for a beach nourishment project sea area at Longfengtou Beach was set up based on MIKE 21 by using a twolevel nested grid. The calibrated model was then adopted to simulate the flow fields and wave fields before and after the project, and the hydrodynamic responses to the nourishment project were analyzed. The simulation results show that the tide in Pingtan sea area is regular semidiurnal and the average tidal range at spring tide in August is about 5 m; the tidal current in Haitan Bay is of typical reversing current with a large flow velocity in the mouth of the bay, and a small and the smallest flow velocity in the middle and top of the bay respectively; the northern breakwater, which greatly reduces the northsouth water exchange, adjusts the ebb current along the breakwater; the flow velocity at the tip of the breakwaters increases due to the deflecting flow, and an anticlockwise circulation generates obviously; the northern and southern breakwaters only have a limited effect on the area behind the breakwaters where the wave height significantly decreases, and the influenced length of shoreline is slightly greater than that of breakwater; the wave height at the tip of breakwaters increases due to the energy convergence caused by wave refraction. Overall, the reduction of wave height and flow velocity in the middle part of the beach is negligible, thus the construction of offshore breakwater is suggested to strengthen the protection of Longfengtou Beach.