The Study On The Hydrodynamic Affected By Shoreline Changes During The Past 60 Years In Jiaozhou Bay

Jiaozhou Bay is an essential condition that Qingdao exists and develops, which plays an important role in port,marine transport,aquaculture industry and travel.With the rapid development of urbanization and economy, water area of Jiaozhou Bay has shrinked tremendously in recent years, which results lots of potential hazards of the decrease of tidal prisms,reduction of the ability to regulate climate,changing of the flow field,lessening of the intensity of hydrodynamic,reducing of water exchange and the capacity of carrying sand,diminishing of the environmental capacity of the harbour,deteriorating of ecological environment and so on.According to the complex terrain, flexural coastline and the large area of beaches of Jiaozhou Bay,3-D hydrodynamic numerical model EFDC is used to simulate the area. The hydrodynamic environment of the Jiaozhou Bay in the 1952 and 2008 is simulated, which contains tidal water capacity,tide,current and water exchange. The stimulations data are compared, and the variation rule of Jiaozhou bay coastline dynamical environment changes is quantifily analysed during the changes of Jiaozhou Bay coastline and the reducing of the area in different periods.Based on hydrodynamic numerical model EFDC,the modifiedσcoordinate-LCLσcoordinate is introduced in vertical direction, and only tidal forcing-M2,S2,Ol,K1 are concerned in open boundary.The hydrodynamic environment of the Jiaozhou Bay in the 1952 and 2008 is respectively simulated, which obtain the distribution condition of tidal current fields and residual current fields.Water concentration is introduced and it is combined the water quality formula to compute the water exchange.Tthe water age of Jiaozhou Bay is calculated based on the hydrodynamic of EFDC.According to the formula of tidal prisms, the tidal prisms of Jiaozhou Bay are computed in different period.The coastline,water depth and sea area of the entire Jiaozhou Bay has been changed obviously in the recent 60 years due to Human Activities and the coastline of natural evolution. The coastline of Jiaozhou Bay has reduced from 206.41 km in 1952 to 178.06km in 2008;the sea area is 540.3 km2 in 1952 while 348.07 km2 in 2008;and at the same time, the isobath of the shoal water is basically shrinked toward interbay. During the spring tides, the tidal prisms of Jiaozhou Bay has reduced from 16.29×108m3 in 1952 to9.57×108m3in 2008;while during the neap tides,the tidal prisms in 1952 was 11.07×108m3, cutted down by 40 percent. The velocity of Jiaozhou Bay shows the trend of decrease. The maximum velocity ruduces by 90cm/s; and the velocity and direction of the tide change the more largely the more nearer the tideland. After the Huang island was connectted with land, the residual current velocity of the two strong gyres related to the Huang island not only becomes smaller, but also the center of gyres move to southeast. The topography of the northern sea of Jiaozhou Bay has gotted great change, which results the residual current fields of the area gets weaker or disappear directly. The time of water exchange of Jiaozhou Bay has increased dramatically from 59 days in 1952 to 80 days in 2008.Comparing the time of water exchange of the surface and bottom, it is not more than one day due to strong mixedtide.