2020 Fiscal Year Final Research Report

Innovation of beach nourishment technology for erosion control based on multi-aspect analyses of beach topography and sediments

Research Project

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Project/Area Number	18H01539
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	Kochi University of Technology
Principal Investigator	SATO Shinji 高知工科大学, システム工学群, 教授 (90170753)
Co-Investigator(Kenkyū-buntansha)	田島芳満東京大学, 大学院工学系研究科(工学部), 教授 (20420242) 山中悠資東京大学, 大学院工学系研究科(工学部), 助教 (60815108) 下園武範東京大学, 大学院工学系研究科(工学部), 准教授 (70452042)
Project Period (FY)	2018-04-01 – 2021-03-31
Keywords	海岸過程 / 海岸侵食 / 海岸保全施設の設計 / 養浜
Outline of Final Research Achievements	Beach trench surveys were conducted on sand gravel beaches in Miyazaki and Kochi Coast. The survey in Kochi Coast was conducted on a beach protected by detached breakwaters. Alongshore and cross-shore trenches were excavated with a total length of 150m. The trench faces were recorded by a RTK-UAV and compared with topography data. A clear boundary between sand and gravel layers was observed at a level of 2m above sea level. The bottom gravel layers were considered to be developed by swash waves at the construction of detached breakwaters. The beach was found to be eroded by several high waves in last 15 years. The erosion level, however, was found to be up to the level of sand-gravel boundary, which implied that the sand gravel beach protected by detached breakwaters was resistant to erosion owing to the presence of buried gravel layers.
Free Research Field	海岸工学
Academic Significance and Societal Importance of the Research Achievements	海岸地形変化の研究は，地形測量や底質の分析などに基づくものが多いが，これらは，地形表面の特性を分析するもので，海浜の内部構造を解明することはできない．本研究では，海浜のトレンチ調査を実施し，砂礫海岸の侵食耐性を科学的に検証することができた．砂礫海岸における離岸堤背後の海浜形成が10年以上の長期にわたって継続すること，形成された海浜の深部には礫の集積が見られることが明らかとなった．離岸堤などの海岸保全施設の建設による海浜安定には，波浪の制御だけでなく，建設後に形成される海浜内部への礫の集積も大きな役割を果たしていることが明らかとなり，今後の養浜工の最適設計に活用できる資料を取得することができた．