Study Of Sedimentary Dynamic Character At The South And The North Changshan Islands Sea

The Changdao County locates at Bohai straits which is the border of the Bohai Sea and the Yellow Sea, and in the south of Liaodong, and in the north of Penglai. It is at the throat of the Bohai Sea. The Changdao County mainly composes of the South Changshan Island, the North Changshan Island, Daheishan Island, Miao Island and so on. The South Changshan Island and the North Changshan Island have been connected by connecting islands dam since 1960. The great change about dynamic condition have take place in the west of dam. The water quality and ecological environment become worse. Sediment silted. Shandong provincial party committee and government make the strategic decision-making to build the South and the North Changshan Islands Bridge in order to improve traffic conditions on the island, to renovate and renew marine ecological environment, to promote the economic development of island. That makes it possible to remove the connecting islands dam.The paper bases on depth and terrain for many years, hydrometeorology, terrain, and so on both of measured and of historical data. It simulates current field, wave field and changes of topography at the South and the North Changshan Islands Sea by ECOMSED model and SWAN model. The results show that:The tidal wave is forward wave in the South and the North Changshan Islands. Maximum velocity comes forth at high and low tide. Flow changes appear at the middle of ebb and rise tide. At low tide water flows from the Bohai Sea. As a whole the direction is from west to east. The average velocity of flow is between 30cm/s and 40cm/s at surface layer. Blocked by Daheishan Island the current is divided to the south offshoot and the north offshoot. The north offshoot flows to southeast after passed Changshan channel and then round north of the North Changshan Island. The south offshoot flows to east after passed Dengzhou channel and then round South Changshan Island and converge with north offshoot. At high tide water flows to the Bohai Sea. As a whole the direction is from east to west. The average velocity of flow is between 20cm/s and 40cm/s at surface layer. Blocked by the South and the North Changshan Islands the current is divided to the south offshoot and the north offshoot. The north offshoot flows to west after round north of the North Changshan Island. The south offshoot flows to south~southwest after round the South Changshan Island. The 13% wave height of 50-year return period is 4.0m～6.5m at east of the South and the North Changshan Islands, however it is 1.0m～3.0m at west. As a whole the region is erosion. Strong erosion region is mainly located at south and north of Daheishan Island, at north of Xiaoheishan Island and at east of North Changshan Island. Maximum erosion rate is 4.5cm/a. Deposition zone mainly locates between the North Changshan Island, the South Changshan Island and Miao Island. Siltation rate is between 0.5cm/a～1.4cm/a. Maximum siltation area locates at west of the connecting islands dam. Siltation velocity is 1.4cm/a.The impact of removing connecting islands dam at current, wave, topography, erosion and deposition mainly locates at its two sides. Maximum velocity of flow change is 45cm/s at the removing dam. Velocity change is less than 1cm/s at about 2.0km east of dam. Velocity change is less than 1cm/s at about 4.7km west of dam. Compared with south wind, wave height changing most is east wind. The area that wave height of 50-year return change more than 0.1m is about 5.94km2 before and after removing the dam. It mainly locates at the west of the dam. The sea between the South and the North Changshan Islands, Miao Island is from siltation to erosion. Maximum erosion velocity reaches 8.1cm/a. Erosion velocity reduces year by year and reaches balance at last.