Numerical simulations of cohesive sediment transportation in coastal waters considering time-dependent sediment resuspension and deposition

The Ariake Sea, which is a typical semi-closed bay located in Kyushu Island, western Japan, has a maximum tidal range of about 6m in spring tide and has vast tidal flats composed of both sandy bottom areas and muddy bottom areas. In this study, 2-dimensional depth-averaged finite difference numerical models have been developed for predicting the tidal flow velocity and suspended sediment concentration in the Ariake Sea. In the suspended sediment transportation model, time-dependent sediment resuspension and deposition were modeled as response to the tidal flow by considering the presence of cohesive bottom sediment. The model results were compared with the in situ measurements of suspended sediment concentration and tidal flow velocity at several stations in Isahaya Bay located at the western part of the Ariake Sea, and with the concentration map of suspended sediment concentration estimated from the Landsat Thematic Mapper image. The results indicated that the models were able to accurately reproduce the measured values of suspended sediment concentration and tidal flow velocity and the estimated general pattern of the concentration map.