Gu Tsui Surrounding Sea Sediment Particle Size Characteristics And Seafloor Topography Changes

From the granularity analysis of surface sediment at shallow sea around the Gulong Headland, together with geological and hydrological data, the effect of coast shape on the sediment grain size has been discussed. The mean grain size of surface sediment is thinning from shore to the sea in shallow area of bay, but fined in the area of medium-depth and around the headland. The sorting cofficient is poor except sandy area in the Xiandao bay. Most of skewness is normal and near normal. Kurtosis is diversity and leptokurtic The Sediments are mainly clayey silt and sandy silt in the studied area. There is a S-shape distribution zone of clayey silt from north-east to south-west by Gulong Headland. Sediment gradually changes from sand to silt around Xiandao bay area. The main hydrodynamic of sediment transport are tide and wave. The headland affectes the distribution of sediment grain size .Trend analysis shows that the sediment has a headland gathering transport trends in the whole area.Based on the digital topographic maps of depth measurement in 1954,1969 and 1982, with the combination of the depth data of 2005. the DEM maps of study area are builted. The terrain characteristics of the area studied are analyzed. during the four period, the DEM maps generally show a consistent trend. There is shallow water in Xiandao bay and Bai Shakou bay, while deep water a fan-shaped distribution in the southern tip of South Huangdao and Gulong Headland. The depth of water increase from both sides to the middle of Nanhuang island.The digital data of depth will be adjusted to the yellow sea height system (1956). DEM maps are established respectively. The maps of erosion/deposition changes are obtained by raster analysis of GIS. The whole study area is erosion inshore (except Xiandao Bay) and deposition offshore during 1954 and 1969. From 1969 to 1982, the study area is in state of weak siltation. Between 1982 and 2005, the study area is deposition inshore and mainly in state of weak erosion offshore.