5:15 PM - 6:30 PM
[ACG42-P05] Predictive simulations of redeposition and seawater transportation after a tsunami in Osaka Bay where bottom sediments were disturbed by tsunami
Keywords:Tsunami, Osaka Bay, Marine Bottom Sediment, Simulation, Redeposition, Seawater transportation
Tsunami caused by Nankai Trough Earthquake will disturb marine bottom sediments in Osaka Bay. This disturbance is the first large-scale disturbance for Osaka Bay after the rapid economic growth. The sediments contain several materials such as nutrients, cysts of harmful algae, bacteria and heavy metals. It is necessary to predict the changes in the marine environment and ecosystems caused by tsunamis for the ocean SDGs. Nakada et al. (2018) predicted by the tsunami simulation that the sediments would be disturbed at the inner part (the eastern half) of Osaka Bay. The sediments were disturbed particularly at the mouth of the harbor and estuary, and the total flux for 10 hours after the earthquake is more than 10 kg/m2. Transportation and redeposition of the sediments and transportation of seawater with dissolved materials in Osaka Bay after the tsunami were simulated in this study by ocean models. The transport and redeposition of the sediments were calculated by a tidal simulation. The deposition rate was given by the Stokes’ low. The sediments were redeposited along the shore line and Okinose where the water depth was shallow and along the oceanic fronts by the tidal residual current as the results of the calculation for one month after the earthquake. Seawater transportations were simulated by the three-dimensional ocean model, FVCOM. Calculations were carried out for six cases for two months with different timing of earthquake occurrence every two month. The path and speed of seawater transportation inside Osaka Bay, and the timing and speed of outflow from the bay were different for each case.