STUDY ON EVOLUTION OF SCOURING AND SILTING SYSTEM IN THE NEARSHORE FROM SANSHAN ISLAND TO SHIHUZUI

Based on surficial samples, depth data and Landsat remote sensing images, the characteristics of surface sediment, shoreline change, and scouring and silting pattern have been studied in the offshore area up to the 8 m of isobath from the Sanshan Island to Haibeizui. Results show that there are 4 types of surface sediment in the study area, i.e. sandy silt, silty sand, pebbly sand and sand. Shoreline is retreating in the whole region. The retreating rate from the Sanshan Island to Haibeizui is 2.5m/a in 1995-2005, and 2 m/a in 2005-2015. The retreating rate of shoreline from Haibeizui to Shihuzui is 2.5 m/a during 1995-2005, and 3.5 m/a during 2005-2015. The study area is under erosion during the period of 2004~2015. Due to the effect of offshore construction programs, the bay to the southwest of Haibeizui cape is under deposition during the period of 2004-2007. It turned to erosion from 2007 to 2015; the west of Haibeizui from 300 m to 1 200 m in width is under an erosion state during 2004-2007, and became deposition during 2007-2015. Wave is the dominant factor of erosion and deposition. Human activities, such as offshore constructions, have played significant roles.