Tidal Flow Simulation for the Effect of Seabed Configuration on Exchange Rate of Sea Wafer in Omura Bay

Abstract

in Nagasaki Prefecture, which is almost isolated from the outer sea, is famous for the very low exchange rate of sea water. In the present paper, the authors carry out the tidal flow simulation using the simulation system improved with the automatic control method, and it is discussed that the effect of seabed configuration on the exchange rate of sea water in Omura Bay. At first, it was estimated that the current rate ranges from 0.2 to 0.4%. Secondly, the authors performed the simulation tests with the modified seabed configuration which is cut the sea mount and buried the deep basin, respectively or simultaneously. It was confirmed that there are little changes of tide, the averaged rates become higher than current one and the water mass pattern nearby the bay mouth stretches into the depths of the bay .

Material Balance of Phosphorus in a Semi-Closed Bay Calculated with Actuality Measurements and Data of an Observation Satellite over a Long Period.

“…Calculation of the Exchange Rate of Seawater with Tides and the Total Amount of Phosphorus in Sediment ---Hyodo and Gotoh estimated that the exchange rate of seawater from Omura Bay to the open sea was about 0.2% to 0.4% in a single tide. 21) An exchange amount of seawater per year was calculated in a progression using 0.3% as the exchange rate. The amount of phosphorus in the total coastal sediment at the bottom of the bay was calculated using a phosphorus concentration of 0.7 mg/g in the sediment, a surface area of 320 km 2 in the bay, a thickness in 10 cm of the sediment and a density in 1.3 g/cm 3 of the sediment.…”