Elucidation of potential natural habitat structures of river estuaries based on the relationship between geomorphologies and controlling factors

2022 Fiscal Year Final Research Report

• Project/Area Number: 19H02250
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 22040:Hydroengineering-related
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Itsukushima Rei 東京工業大学, 環境・社会理工学院, 助教 (30737656)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 河川汽水域 / 生息場構造 / 河川地形 / 環境要因 / 人為的インパクト / 環境再生

Outline of Final Research Achievements

This study was conducted to elucidate the relationship between river estuarine habitat structure and environmental factors at multiple scales, and to identify potential natural geomorphology that can be goal of environmental restoration. The classification of river estuarine habitat structure of 93 rivers located in eastern Japan resulted in three groups: rivers on the Pacific Ocean side dominated by sand bed and run, rivers on the Sea of Japan side dominated by gravel bed and rapid, and rivers dominated by sand bed and glide. Decision tree analysis revealed that watershed and segmental scale factors were influential factors in the classification. Gravel bed tended to be more prevalent in rivers with smaller dam catchments, suggesting that changes in the supply of gravel due to dams may affect the environmental structure of river estuaries.

Free Research Field

河川工学

Academic Significance and Societal Importance of the Research Achievements

本研究の成果に基づき、「環境構造が多様な保全すべき汽水域」や「環境再生の目標となる環境構造」を設定することができる。また、人為改変と環境構造の関係を明らかにするとで、汽水域の再生を行う際に「どの人為影響を改善すべきか」が明瞭となり、再生に向けた実効性の高いシナリオを策定できる。更に、継続して人為影響を受ける汽水域の環境構造改変を予測することが可能となるなど、河川汽水域の再生、保全に大きく貢献する。また、研究対象とする中小河川は、立地条件が多様であるのに対し、河道特性を整理した事例が少なく、研究成果は河川管理の基礎的情報として活用可能である。