SEDIMENT CHARACTERISTICS AND HYDRODYNAMICS OF NEARSHORE GUDONG IN THE YELLOW RIVER DELTA

The sediment stirring-up and transporting have been studied based on the data of wind, tidal currents and bottom sediments observed during the period from 2004 to 2006. The results show that sedi-ments at the Gudong coasts are mostly silt and poorly-sorted. Sediment particles become finer and poorersorted with water depth. Influenced by wind-residual currents, coastal line and groynes, sediments show different transporting trends in different regions. Analysis of sediment grain-size tendency shows that the study area can be divided into three areas:in the north embankment nearshore area of Gudong, sediments are mainly transported towards northeast;in the east embankment nearshore area, sediments go from north to south except the area between NO 2 Groyne and NO 18 Groyne where sediments show an opposite direction of transportation; in the Xintan area of the Yellow River delta on the south side of Gudong, sediments migrate from west to east. Tidal current velocity is not great enough to stir up bottom silt in the nearshore Gudong, but silt is often suspended by waves around groynes that have made tidal currents change. Waves are often seen to be 1.0 m high,and silt suspension is concentrated in area shallower than 5 m of water depth. Silt stirred up by waves is carried to open sea by tidal currents. Erosion becomes serious due to short of silt recharge.