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Even though models of water quality have become increasingly detailed over time, their applicability to analyze long-term effect on sedimentary bed formation is yet to be clarified. Hence, an integrated, layer-resolved, process-based, sediment-water coupled, long-term robust, three-dimensional (3D) ecosystem model, including realistic sedimentary and pelagic processes, was developed. The constituents of the integrated model included a multi layered ecosystem model, a quasi-three dimensional hydrodynamic model, a wave hindcasting model, and a sediment deposition and erosion model. Because numerical modeling difficulties arise in setting the initial conditions, especially for a sedimentary bed, this novel modeling approach suggests to initiate the model with the simplest initial conditions of no particulate organic carbon content (POCC) and uniform inorganic sediment distribution. The model was applied to Tokyo Bay and quasi-steady state POCC in the sediment was obtained through long-term computation with realistic sedimentary and pelagic processes. Wave induced bed shear stress (WBSS) is critical for sediment erosion and spatial movement of sediment pollution, while a stable morphology is determined by the balance between the current induced bed shear stress (CBSS) and WBSS in Tokyo Bay. This novel modeling approach, with the simplest sedimentary initial conditions and realistic sedimentary and pelagic processes, provides a great tool for long-term ecosystem modeling in future studies.

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Typhoon-induced wave overtopping is a combined result of astronomic tide, storm surge and wave runup. However, in present practice the cause and the extent of damage due to typhoon is investigated using storm surge simulation models and wave simulation models independently where there is no consideration of tide-wave interaction. Hence, the application of a coupled model is expected in future practice to obtain more realistic results and thereby to determine the exact cause and the extent of damage. In addition, it is important to increase the spatio-temporal resolution of input forcing to accurately reproduce the typhoon phenomenon. Hence, the objective of this study is to analyze the typhoon-induced storm surge with COAWST (Coupled-Ocean-Atmosphere-Wave-Sediment Transport) modeling system which is forced by three different types of modelled forcing with three different spatio-temporal resolutions.The COAWST model with ROMS (Regional Ocean Modeling System) as the ocean model and SWAN (Simulating Waves in Nearshore) as the wave model was used to analyze the typhoon-induced storm surge due to a number of strong typhoons struck Japan in the recent past. WRF (Weather Research and Forecasting) model was used independently as the atmospheric model. Computed model results were compared with the tidal observational data and wave observational data with respect to each forcing. Thereby, the significance of sptio-temporal resolution of forcing on model results were discussed at the end of this study. COAWST model could well reproduce the typhoon phenomenon and model results were consistent while the results were highly sensitive to the spaio-temporal resolutions of input forcing.

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