CHARACTERISTICS OF CURRENTS INDUCED BY HEAVY RAINFALL IN HIROSHIMA BAY IN JULY 2018

Abstract

 Mooring observations and numerical model analysis were conducted to investigate characteristics of currents and behaviors of riverine water discharged into Hiroshima Bay by heavy rainfall in July 2018. The tidal and residual flows obtained by numerical calculation were consistent with the observation results. The calculated values of surface salinity distribution due to the heavy rainfall were also in good agreement with the ocean color satellite imagery. The less saline riverine water moved southward in the western part of the bay and was distributed over ten days throughout the bay. After the heavy rainfall, a strong southward (outflow) residual current from the north along the west coast was calculated in the first layer. In the second layer, however, an inflow current was calculated in the northern part of the bay. The discharged riverine water was considered to outflow through the surface layer. We also discussed the influences of changes in the currents and marine environments caused by the heavy rainfall on seedling collection of Pacific oysters.