Short to medium-term sediment transport at a river mouth and hydro-morphodynamic features at a multiple sandbar beach

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K04363
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 22040:Hydroengineering-related
• Research Institution: Kanazawa University
• Principal Investigator: Umeda Shinya 金沢大学, 地球社会基盤学系, 教授 (30313688)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 海浜変形 / 河口・海岸水理 / 底質輸送 / 砂州 / 汀線変動 / 波の遡上 / 波浪 / 洪水

Outline of Final Research Achievements

For understanding of sediment transport and morphological response of terrace and sandbar due to large summer flood and high-energy winter waves, the hydro-morphodynamics at the mouth of Tedori River, Japan have been investigated using the process-based numerical model. The wave direction of the stormy waves with over 3 m height become a dominant factor in transporting sand to beach and river channel during the erosion process of river mouth terrace induced by annual maximum flood.
Characteristics of short and infragravity wave propagations and runup on a multiple sandbar beach have been investigated by comparing with observational data of cross-shore profile and wave and the results of systematic numerical simulation. The sandbars reduce wave runup of stormy wave with over 1-2 m height, while the sandbars enhance wave runup of moderate wave around 0.6 m high. The cyclic change of sandbar configuration plays an important role in keeping shoreline around equilibrium position.

Free Research Field

海岸工学

Academic Significance and Societal Importance of the Research Achievements

河口・周辺海岸における土砂移動過程に関する知見は，海岸侵食の問題に対処するため有用である．土砂の質と量を考慮して時間スケールの異なる洪水と波浪による一連の河口域の水理・土砂動移動現象と地形変化を捉えた本研究は希少であり，工学的な価値がある．
波の遡上高の変動特性は，対象海岸の利用・保全方法を議論する上で役立つ．また，長周期波を考慮した遡上高と汀線位置や砂州配置との関係性の議論は，国内外の砂州海岸の海浜変形の基本特性や地域特性に関する知見を得る上で有用で，学術的な価値があると考えられる．