Resuspension And Clearing Of Dredge Spoils After Dredging, Cleveland Bay, Australia

During dredging operation, fine sediment is released in the navigation channel of the Port of Townsville. Australia, as a result of mechanical disturbance of the bed and of the overflow from the storage tanks of the dredger. Some of this sediment is advected away from the dredging site toward the beach and reef areas and could result in environmental damage if not managed properly. Field monitoring was conducted for salinity, temperature, suspended sediment, and acoustic profiles at several sites before and after dredging. Laboratory investigations on the effect of sediment concentration, turbulence, and floc size on the clearing of a suspension column were also undertaken. Results of both field and laboratory investigations show faster clearing in quiescent conditions than in turbulent conditions. Turbulence at low levels disturbs the dewatering microchannels of the fluid mud layer. As turbulence increases the effect of floc breakage and settling retardation also become important.