The Research Of Effects On Near-shore Water Environment Resulted From The Change Of Coastline

Coastal waters are very closely related to human living and economic development in coastal areas, in recent years as the developing of economic, because of the influence of natural factors and human activities, the coastline has been changing. As the forefront of interaction between coastal and ocean, the changes, on one hand is the response to the effects from the dynamics, on the other hand is also a direct reflection of the evolution of the coastal environment, to some extent reflects the changes to Near-shore water resulted from human activities. In the paper, three-dimensional finite volume hydrodynamic model with unstructured grid are adopted to study the impacts of changing coastline on the coastal water environment.To begin with, according to the features of shoreline and the basic elements of water environment, the paper selects the flow field, tidal, tidal volume, water exchange rate, sediment deposition and erosion, environmental capacity and Lagrange Coherent Structure (LCS) as the index of the impacts of water environmental because of changing coastline. After summarized the calculation of each index, it focuses on the basic principles of Water motion analysis.Then based on different terrain, nested fine hydrodynamic simulation would be built. After ensuring the model can reproduce the tidal wave propagation in the Gulf and the tide changes over time, we can get the changes of flow velocity, tidal level, tidal volume, water exchange capacity and changes in FTLE field.Finally, the paper focus on analysis of the small key areas, from the results of statistical analysis, we get the length increased 292.2 km from 1980 to 2005,and the area reduced of about 200 km2. In various types of coastline, Muddy shoreline, sandy shoreline and bedrock shoreline show decreasing trend, and the artificial coastline increases greatly. By the calculation of the hydrodynamic to the top of Liaodong Bay, we can see little change in tidal level of feature points, but changes of points near the shore area significantly larger than the in the middle. And through its Lagrange coherent structure (LCS) in the calculation, it shows the same trends. By the calculation of the water environment in Dalian Bay, we can get that change in tidal level is small, the changes more obvious in the coastal region, few change in tidal volume, the overall show decreasing trend. And the calculations results of water exchange demonstrate that the water exchange capacity in 2005 was better than 1980, but both are in common is that the exchange in the central Bay off the coast better than in three sub Bay. From the Lagrange coherent structure (LCS) point of view, FTLE get large value in coastal shoreline and San Shan Dao, forming distinct sub-block areas of water, and the structure is more complicated in 1980 than in 2005.