A hydrodynamic modeling study to estimate the flushing rate in a large coastal embayment

A three-dimensional hydrodynamics model was applied to a coastal embayment on the west coast of the Korean Peninsula to examine the potential effects of a large reclamation project (the Saemangeum Project). To understand and analyze the impacts of the coastal structures associated with the Project on the hydrodynamics, as well as the composition ratio of the saltwater to freshwater, the seasonal distribution of the residence time and flushing rate were examined using the salinity and tracer simulation as dilution indicators. The calibrated and verified model was used to examine changes in the tidal elevation, salinity, residence time and flushing rate. The results indicate that the completion of the fourth sea dike will limit circulation, and that the salinity inside the dike would be dominated by rainfall and runoff. The flushing rate was estimated to decrease after the construction of the dike, such that biogeochemical changes could occur in the sea water and sediment. From this study, it was concluded that the three-dimensional hydrodynamic model can successfully simulate the changes in elevation, residence time and flushing rate in the Saemangeum Embayment and become a useful tool for determining a management plan to maintain the water quality of coastal embayments.