American Society of Civil Engineers


Development of a Long-Term Predictive Model for Baroclinic Circulation and Its Application to Blue Tide Phenomenon in Tokyo Bay


by Jun Sasaki, (Institute of Environmental Studies, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan E-mail: jsasaki@k.u-tokyo.ac.jp) and Masahiko Isobe, (Institute of Environmental Studies, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan)
Section: Part V Coastal, Estuarine, and Environmental Problems, pp. 3870-3883, (doi:  http://dx.doi.org/10.1061/40549(276)303)

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Document type: Conference Proceeding Paper
Part of: Coastal Engineering 2000
Abstract: Blue tide, upwelling of anoxic bottom waters, is a major problem in Tokyo Bay and observed several times a year from spring to fall. In particular, a large scale blue tide sometimes causes mortality of fish and benthic animals in shallow waters and it is of great importance to clarify the condition under which it occurs. Anoxic waters are produced on the flat bottom at the head of the bay and in trenches, which were dredged for the reclamation of the foreshore. Upwelling of these anoxic waters is mostly induced by a northerly offshore-ward wind. Thus a hydrodynamic model is a powerful tool to investigate the phenomenon. A predictive model for hydrodynamic flows in a semi-enclosed bay is developed. It is a semi-implicit model in sigma coordinates and special considerations are made in capability of long-term computation with high accuracy. As a remedy for the treatment of a steep bottom slope, such as the trenches in the bay, a multi sigma coordinate system is introduced. The model is applied to reproduction of blue tides to discuss the magnitude of them.


ASCE Subject Headings:
Bays
Water pollution
Eutrophication
Fish management
Japan