SUPPLY AND DEPOSITION OF SEDIMENT ALONG THE NORTH BANK OF HANGZHOU BAY, CHINA

Sediment transport and deposition processes were studied on the tidal flats along north Hangzhou Bay (P.R. China) because of the large tidal range, abundant sediment supply and strong seasonal variations. Tidal currents reach a maximum of 8.9 m·s-1. The flood is stronger but of shorter duration than the ebb. Waves come from S-SE during the summer (wet season) and from NE-NW during the winter (dry season). Average waves are 40 cm high, but may reach 4 m during storms. Sediment is largely supplied from the Chang Jiang, small amounts also from the Qiantang Jiang. Sediment supply is largest during the winter. The tidal flats consists of clay, silt and some fine sand; they are 0.6 to 2 km wide. Deposition on the high parts of the flats is enhanced by tidal asymmetry while up-slope transport of sediment is increased by a turbulent front that develops during the flood. Erosion on the flats takes place mainly during summer storms (typhoons), when wave-cut puddles and scarps are formed. In the upper part vegetation reduces the effect of storms and mainly laminated sediment is present. © 1990.