No.259 研究課題 / Project
大気―河川―内湾系連成モデルに基づく多摩川河口域の物質循環解析―東京湾が多摩川の水質環境に与える影響に着目してThe analysis of sediment and heat transports at the Tama River Estuary and a development of atmosphere-reviver-estuary combined model. -Influences of Tokyo Bay water on the water environment in Tama River Estuary-| 学術研究 Academic Research |
No.259 |
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| 代表研究者 Principal Investigator |
八木 宏 Hiroshi Yagi |
| 所属（採択当時） Affiliation |
東京工業大学大学院情報理工学研究科情報環境学専攻 助教授 Tokyo Institute of Technology |
| 研究内容要約 Research Summary |
東京湾が流入河川の環境形成に与える影響を、底質輸送と熱環境に着目して現地調査及び数値モデルの開発を行った。底質輸送に関しては、東京湾の影響を強く受けた多摩川河口域の基本的な流動構造を明らかにした上で、潮汐振幅の変化や流量の大小により流速分布や底面せん断力の特徴が一致が変化し、これに伴って底質は上流向き輸送（標準的な大潮時）、正味の輸送量が小（潮位差が大きい大潮時）、下流向き輸送（流量が大きい大潮時）のように大きく変化することを示した。熱環境については、過去30年間に東京湾及びその流入河川の水温が冬季に顕著な大きさで上昇（東京湾内：0.03℃/年、河川（荒川）：0.1℃/年）していること示した上で、東京湾―河川の熱交換構造について大規模な集中観測を実施し、冬季の東京湾から河川への熱供給を定量的に示した、さらに、沿岸域―河川間の物質循環を解析するために、沿岸域～河川域という浅水域に適したSDS & Q3D モデルを発展させることで、河口干潟域の干出まで評価可能な流動・底質輸送モデルの構築を行った。 The objective of this study is to understand the influence of Tokyo Bay on the river and estuarine environment, focusing especially on the fine sediment and heat transport processes around the river mouth. Firstly we conducted the intensive field surveys in the Tama River Estuary in 2002. The fundamental characteristics of velocity and fine sediment transport processes, which strongly depend on the tidal range and river discharge, were revealed by the measurement results. Secondly, to understand the heat environment in Tokyo bay and inflowing rivers, long-term trend analysis of water temperatures and intensive field measurements of heat flux in the estuary were conducted The results of the long-trend analysis revealed that water temperatures have been increasing in winter during the past 30 years, the rate of increase being 0.03℃/year in Tokyo Bay and .01℃/year in inflowing rivers ( Ara River and Tsurumi River ) . The intensive field measurement shows that the heat is supplied from Tokyo Bay to the river in winter and the flux is around 10 times larger than that between atmosphere and river. Furthermore, a numerical model to analyze the interaction process of sediment and heat transport between bay and inflowing rivers has been developed in the present study. |
| 共同研究者 Collaborators |
神田 学（東京工業大学大学院理工学研究科国際開発工学専攻） Manabu Kanda (Tokyo Institute of Technology Graduate School of Science and Engineering, Department of International Development Engineering .) |
| 研究全文 Full Text |
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