FIELD MEASUREMENT ON FLOC PROPERTIES OF RIVER-DERIVED COHESIVE SEDIMENTS IN A PORT AT A RIVER MOUTH

Abstract

 For efficient maintenance dredging of estuary ports, it is important to understand the mechanism of sediment deposition in the port. In this study, the particle properties of suspended sediments transported from Shinano River into the Niigata Port (the West Port District) were investigated by water sampling analysis and in-situ measurements based on laser diffraction and image analysis methods. The suspended sediments were rich in organic matter and consisted mainly of clay and silt fractions. In-situ particle measurements indicated that the cohesive suspended sediments in freshwater were transported into the port as freshwater flocs, and that the floc sizes increased further in seawater. These settling processes with flocculation, caused by the presence of organic matter and contact with seawater, are important physical processes that should be appropriately implemented in predicting sedimentation problems in estuarine ports. In addition, the reliability of the floc sizes obtained from the in-situ measurements is discussed.