INTERCHANGE OF WATER-SEDIMENT-SALINITY OVER AN INTERTIDAL FLAT IN JIUDUAN SHOAL IN THE CHANGJIANG RIVER ESTUARY
LI Peng;YANG Shi-Lun;QIN Wei-Hua;Forecast Centers for East China Sea State Oceanic Administration of China;State Key Lab of Estuarine and Coastal Research,East China Normal University;
To understand the interchange of water-sediment-salinity in the tidal flat of Jiuduan Shoal, Changjiang(Yangtze) River estuary, the water depth, turbidity, salinity, speed and direction of vertical current, and echo intensity were measured using OBS-3A and ADP-XR during spring tide in summer and middle-spring and neap tide in winter. Results show that:(1) the average speed of vertical current in winter middle-spring and neap tide were 15.9 and 8.4 cm/s, respectively, while in summer the current speed reached 26.5 cm/s. The biggest speed during observation in summer and winter were 84 and 35 cm/s;(2) salinity was higher in winter than in summer, in the ranges of 0.65–4.91 in summer(2.14 in average) and 3.5–10.28 in winter(6.28 and 7.98 in middle-spring and neap tide in average);(3) high SSC(suspended sediment concentration) occurred during shallow water stage at the beginning and the end of inundation. The average SSC was higher in flood period than in ebb period. The average SSC became higher from surface to bottom gradually;(4) The discharge of water and salinity in-and-out the tidal basin were in balance, while about 40% of sediment discharge transported during flood tidal period was detained in the tidal basin. The average sediment discharge carried during every tide was 6102kg, and the accretion rate was 0.0112mm/tide. The results show that the tidal basin was in accretion at rate of 8.2mm/year.