Research On The Effects Of Donghai Dam On The Hydrodynamic Environment Of The Zhanjiang Bay

marine engineering at the estuary and coastal areas is important to the the development of human society, proper marine engineering do great significance to local city's economic development, social development will be promoted, and people will be benefited, however, excessive narine engineering without scientific basis would have some bad impact on hydrodynamic environment, water quality, zoology environment of local coastal waters, and maybe bring serious consequences that can not be resumed. The negative impact brought by the marine engineering has been much concerned now, but there's few research on the change of hydrodynamic environment now.This article research on the effects hydrodynamic environment of Zhanjiang Bay because of the built of the Donghai dam between Zhanjiang City and donghai island, after the analysis of the measured data, we found that the tide and tide current at each side of the dam is different, so we set up a 3-D unstructured-grid, free-surface, primitive equation, Finite-Volume Coastal Ocean circulation Model (FVCOM) to simulate the hydrodynamics processes changed by the donghai dam in Zhanjiang Bay, FVCOM combines the advantages of finite-difference methods for simple discrete coding and computational efficiency and finite-element methods for geometric flexibility. Thus, it is a better choice to use FVCOM for solving the difficulty on fitting the irregularly coastal lines, barrier island complexes for numerical simulation in Zhanjiang Bay. After model calculation, the results agree well with the observation. So this simulation can offer more hydrodynamic information to us.we set up another model, remove the inter tidal zone, nouse the wet/dry module, rebuilt the model, compared with the two results, we found that the result nouse the wet/dry module is difference to the reality, the main tidal amplitude and phase is much more smaller, the velocity of tidel current is smaller, water volume and waterchange rate is decreased, it is different to the reality, so it is important to use wet/dry module at a large inter tidal zone area , and the inter tidal zone is importent to the hydrodynamic environment of the bay.Based on the simulation, we can compare the change of tide, tidal current, current field and water exchange of the Zhanjiang Bay between with and without the Donghai dam. By comparing the two hydrodynamic environment results between with and without the Donghai dam, we can have the conclusion: After the dam were built in 1958, great change occurred on the tidal amplitude and phase, tidal current field, of the Zhanjiang Bay. After the dam was built, the tidal amplitude and phaseat the west side of the dam is larger than before, and the current direction is totally reverse, current velocity at the east side of the dam is much smaller than before. Because of the builr of the dam, the water volume of the zhanjiang bay reduced from 788 million m3 to 721 million m3, the water half-life time of zhanjiang bay extended from 45.8 days to 80.6 days,the rate of water change is decreased, especially at the east side of the dam, the water half-life time here extended from 12 days to more than 100 days, so the built of donghai dan caused negative influence on the hydrodynamic environment of the Zhanjiang Bay. Then, we use particle tracing module to simulate the the track of the particle, to show the particle's way out of the bay.