Hydrodynamic characteristics of a fringing coral reef on the east coast of Ishigaki Island,southwest Japan |
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Authors: | H. Tamura K. Nadaoka E. C. Paringit |
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Affiliation: | (1) Frontier Research Center for Global Change, Climate Variations Research Program, Japan Agency for Marine-Earth Science and Technology, Yokohama 236-0001, Japan;(2) Department of Mechanical and Environmental Informatics, Graduate School of Information Science and Engineering, Tokyo Institute of Technology, Tokyo 152-8552, Japan;(3) Department of Geodetic Engineering, College of Engineering, University of the Philippines Diliman, Quezon City, 1101, Philippines |
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Abstract: | To investigate the characteristics of currents on a fringing coral reef, a field survey was conducted, mostly under weak wind conditions in summer, on the east coast of Ishigaki Island, southwest Japan, which is encompassed by well-developed fringing reefs. For the same study period, numerical simulations of the current were also performed using a shallow water turbulent flow model with high accuracy reef bathymetry data, which were estimated from high-resolution imagery obtained from satellite remote sensing. The numerical simulation results showed good agreement with the observed data and revealed that the currents have an appreciable magnitude of tide-averaged velocities, even during neap tides, which are governed mostly by wave set-up effects. The results also indicated that temporal variations in velocity and water surface elevation during a tide cycle in the reef exhibit highly asymmetrical patterns; in spring tides especially, the velocities around channels indicate rapid transitions over a short period from peak ebb flow to peak flood flow. The simulations also indicated that a big channel penetrating deeply into the reef attracts the tide-averaged mean flow, even from distant areas of the reef. |
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Keywords: | Fringing reefs Water currents Numerical analysis Hydrographic surveys Japan Ishigaki Island |
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