Sakawa River plume in Sagami Bay, Japan under weak wind condition: numerical simulation of coastal ocean dynamics and in situ observations for validation

• Published in: Journal of marine science and technology 2024-03, Vol.29 (1), p.221-243
• Main Authors: Arai, Riwa, Nishi, Yoshiki, Fujiwara, Yasunori, Zhao, Jinrui, Jamil, Muhammad Zeeshan
• Format: Article
• Language: English
• Subjects: Automotive Engineering; Engineering; Engineering Design; Engineering Fluid Dynamics; Mathematical models; Mechanical Engineering; Numerical models; Ocean dynamics; Offshore Engineering; Original Article; Regression analysis; River discharge; River flow; River plumes; Rivers; Salinity; Salinity effects; Simulation; Surface salinity; Tidal currents; Water discharge; Water levels; Water transport; Wind
• ISSN: 0948-4280; 1437-8213
• DOI: 10.1007/s00773-024-00985-6

This study proposes a method for estimating river plume length from water levels and river discharge rates. A numerical model for coastal ocean dynamics was refined by comparing thermohaline fields calculated using the model with those measured off the mouth of the Sakawa River in Sagami Bay, Japan. The model successfully captured the reduction in salinity within the surface 1.0-m layer caused by riverine water transport. The simulated surface salinity maps revealed that the dynamic motions of the river plumes were primarily driven by one of the two diurnal occurrences of tidal current intensification. Regression analyses of the simulated results demonstrated that the river plume lengths were closely correlated with the water levels and river discharge rates, and that they could be accurately estimated from preceding river discharge rates under weak wind condition.