INVESTIGATION OF EFFECTS OF SALINITY AND TURBIDITY ON THE MOVEMENT OF MUDDY WATER PLUME FROM THE RIVERMOUTH

Abstract

 Fresh water due to the flood from the rivermouth is transported as the mud water plume, so that sediment transports and morphodynamic changes outside the rivermouth are stongly depended on the salinity at the rivermouth boundary accompanied with wind, wave and river discharge conditions. In this study, by using the WDM-POM which was a quasi-3D sediment transport and morphodynamic change model developed by authors, and the gRSM which was a river sediment calculation model by authors, movements of muddy water plumes were investigated by changing the salinity at the rivermouth boundary. From numerical results, it was revealed that high turbidity zones were concentrated almost in the center of muddy water plumes, and velocity fields were varied especially near fresh/salt water fronts compared to homogenious results. The maximum spatially-mean velocity deviation over the whole numerical domain was about 8.0 cm/s as changing the rivermouth salinity from 0.0 to 30.0 ‰. It was due to the strength of muddy water plume and fresh/salt water front. In conclusions, it was shown that to set the accurate salinity at the rivermouth or to conduct simulations with boudanry conditions of rivers at the far upstream was important in order to calculate the accurate flow field inside the rivermouth to estimate sediment tranports and morphodynamic changes of coastal zones.