Formation of Turbidity Maxima in the Yalu River Estuary, China

Tidal cycle measurements of current velocity, suspended sediment concentration, water depth, salinity and temperature at fixed stations, together with water sampling along longitudinal profiles, were undertaken in the macro-tidal, well-mixed Yalu River Estuary during the summer of 1994 and the spring of 1996. The longitudinal distribution patterns of salinity, temperature and suspended sediment concentration, as derived from water sample analysis, show that turbidity maxima are formed within the estuarine waters, with highest suspended sediment concentration exceeding 1.5 kg m⁻³ on spring tides. The turbidity maxima were found to be associated with low salinity water masses. Analysis of interrelationships between current speed, re-suspension of bottom sediment and spatial-temporal variations of salinity with respect to tidal phase indicates that the turbidity maxima of the estuary are formed mainly by re-suspension effects. In this particular estuary gravitational circulation has an insignificant effect on the formation of the turbidity maxima, and, although dispersive effects (e.g. the Stokes drift) on sediment movement are important in addition to river flow induced advective transport, tidal pumping is insufficient for the formation of the turbidity maxima.