Author(s): Kenta Takenouchi; Akihide Tada; Shin’Ichi Sakai; Michihiro Mizunuma; Takehiro Nakamura; Shinsaku Someya
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Keywords: Field observation; Tidal current; ADCP; DBF ocean radar; Red tide; Isahaya Bay
Abstract: In Isahaya Bay, Nagasaki Prefecture, Japan, a big project that consists of the construction of sea-dike and reclamation by drainage reaches the last lap. While the behavior of tidal current in Isahaya Bay has great influence on both advection and diffusion of red tide and anoxic bottom water etc., the hydrodynamic mechanism related to these phenomena is not understood yet. This study deals with the field observations on tidal current by means of both Digital Beam Forming marine radar (Its abbreviation is DBF ocean radar. ) and Acoustic Doppler Current Profilers (Its abbreviation is ADCP. ) in order to reveal the flow characteristic in the middle west area of Ariake Sound. In particular, the former has started since 2005. On the other hand, the latter has carried out nine times since 2001. As a result, it is realized that tidal current along the north coastline of the Shimabara Peninsula is dominant at flood tide and that there is outflow into Ariake Sound from Isahaya Bay near Takezaki Island in the best part of one tidal cycle. Moreover, it is found out that the maximum flood current measured using the DBF ocean radar branches off to both Isahaya Bay and the head of Ariake Sound significantly. It is also obvious that the current velocity obtained by the DBF ocean radar accords with the one measured by the ADCP.
Year: 2007