The Study Of Sedimentary Characteristics And The Erosion And Deposition Trend In LongKou Sang Island Sea Area

Based on other researchers’ results, combined with the historical observation data and the survey data of sediments, currents, tides and waves, we priliminarily study the distribution of surface sediments and the trend of sediments’transportaiton. Furtherly, by contrasting the sea map and data of bathymetry, the erosion-deposition variation of the Sang Island offshore areas is discussed.Collected sediments within the study area were arranged the 184 stations, sample analysis results indicate that the study area there were seven kinds of sea sediment types, they are silt, sandy silt, mud pebbly sand, gravelly sand, sandy gravel, gravel, shell debris, etc. The coast of study area is mainly silty coast, Sang Island surrounding areas are mainly coarse-grained sediments, other area widely distribute sandy silt. Coarse gravel and sand of sediment components, mainly in the coast and near Sang Island, the more fine-grained silt, clay mainly in the far shore area.The sea maps and survey data show that the main type of the study area is erosion from 1975 to 2004 when compared with bathymetric topography and bathymetric profile. The erosion rate is little, generally about 0.5m, which is basically in a relatively stable state. While the erosion changes obviously in the Sang Island, the surrounding of the Yi Island and coastal areas. About 100m range within the east and west sides of Sang Island is mainly in siltation. North of siltation extent is the largest one which is up to 2.0m and the other areas is based on erosion. The south waterways of Sang Island is the largest study area of the erosion scope and range, which is more than 3.0m. The main type of the Yi Island surroundings is erosion, and the south erosion extent is little, which is under 0.5m. The beach in the study area mainly on both sides of GangLuan Harbor Wharf and Huangshui River Estuary.Beach sediment transport in the study area is mainly controlled by wave action, and underwater slope is mainly affected by tide. The direction of net sand transportation in GangLuan Harbor west coastal areas is from east north to west south along the coast line. While the direction of net sand transportation in GangLuan Harbor east coastal areas is from west to east along the coast line. In the Sang Island south waterways, the trend of erosion waterway sediment is east and west affected by tide. Surrounding the north coastal side of Sang Island, the wave acts directly on the northern coast of the Sang Island. Material is eroded down to the area between the two islands with action of wave and tide.