In estuaries, seawater mixing creates unique water environment. Observations on distribution of seawater mixing layer and on water quality were conducted in this study in order to understand the mechanism of seawater mixing and the vertical distribution of water quality. At the point which has deep water depth, the mixing layer changes easily. Suspended material as well as chlorophyll-a have maximum concentration at the upper edge of the mixing layer. In ebb tide phase, phosphorus has its maximum value at the bottom layer.
Laboratory experiment was also carried out in this study to investigate the flocculation process using river bottom mud. The experiment result shows that flocs diameter, which is used for flocculation, are differed by suspended matter concentration.