PREDICTING WATER FLUCTUATION IN COASTAL ENCLOSED LAGOON USING INTEGRATED TWO-DIMENSIONAL SURFACE AND SUBSURFACE WATER MODEL

Abstract

Based on integrated vertically averaged free-surface and subsurface model, detailed analysis was focused on the water fluctuation in the enclosed lagoon caused by tidal movement. It is shown that when porosity of sand is increased, the water storage capacity in sand beach will be increased and the amplitude of vibration in the lagoon will be decreased. On the contrary, when permeability coefficient is increased, the amplitude in lagoon will be increased, and the phenomena of phase lag will be reduced either. Research reveals there is periodical water exchange between lagoon and out sea on the two sides of the sand beach. The procedure of water going into the lagoon happens differently from that of water coming out from lagoon. Because there is over-height in the lagoon, the time of water transporting from the lagoon to the out sea is longer than the reverse procedure and the maximum of water flux in the first procedure is shorter than the later. Further more the water moving from lagoon to open sea usually happens in the initial stage of flood and later stage of ebb, while the reverse procedure happens in the later stage of flood and initial stage of ebb.