Study On The Characters Of Surface Sediment Transport In Dengzhou Shoal Area

Dengzhou Shoal lies in the west of Dengzhou channel, southwest of Changdao Island, north Shandong Peninsula of Penglai City. Dengzhou Shoal, including four underwater sandbars, is a natural body of water sand long term effected by ocean dynamics and basically in a state of dynamic equilibrium. Dengzhou Shoal is in the marine and terrestrial interaction transition zone. Because of the unique location, it becomes a natural barrier to prevent coastal erosion the of Penglai. But since the 80s sand-excavating in Dengzhou shoal area, it increased water depth and so the damaged shoal, losting the original coastal protection function, resulted coastal erosion. Recovering the geological environment of Dengzhou Shoal has a great significance to development and utilization of coastal resources and environmental protection through analyzing the characters of surface sediment transport.The paper is based on the study area for many years hydrometeorological data, including precipitation, wind and other observations, combined with sediment survey data, using different topography's charts, the Mike 21 applied in study. The two simulation are concerned including tidal current and seabed evolutions of erodion in the paper and then the characters of surface sediment transport in Dengzhou Shoal Area are analysed.The sediments of the area can be divided into 11 types:gravel, gravel sand, coarse sand, medium coarse sand, medium sand, fine sand, sandy silt, silty sand, silt, clayey silt, silty clay. Provenance,dynamical environmental and topography are major factors influencing the regional distribution of sediment types. In Dengzhou Shoal area, the sediment is rich in the medium coarse sand. Gravel sand are widely distributed in the east of Dengzhou channel, the west of Dengzhou channel is rich in the clayey silt. The sediment grain size varies from fine to rough then to fine from the south to the north, from the east to the west the sediment grain size varies from rough to fine in the study area.The ebb-dominated current is dominant in the Dengzhou Shoal. The direction of flood tide is SW-NE and the direction of ebb tide is NE-SW. The ebb current period longer than flood current period, the velocity of ebb current is stronger than that of flood current.The scouring and silting simulation shows Dengzhou Shoal, including Chaodaizhou, Errizhou and Sirenzhou is eroded. Xinjinzhou, in the north of Dengzhou Shoal, is in a relatively balanced status of erosion and deposition. The east of Dengzhou channel is strongly eroded and the west of Dengzhou channel is in a micro-deposition status.In the Dengzhou channel, affected by transverse circulations with longtitudinal axes, it forms a loop system with the sediment within the channel and the sediment in the shoal. Because of sand-excavating, there are some pit. These pits′terrain are lower than the surrounding area, so the sediment around the pits have a migration trends to them. The scouring and silting simulation shows the sediment in the south of Chaodaizhou transports towards the southwest. The ebb-dominated current is dominant in the study area, the sediment generally transports from northeast to southwes, in line with the trend that from east to west surface sediments gradually varies from coarse to fine.