Plan for improvement of fish passing upstream in steep stream-type fishway

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K04280
• 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: Toyo University
• Principal Investigator: AOKI Muneyuki 東洋大学, 理工学部, 准教授 (00712853)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 水路式魚道 / 急勾配 / 粗度群 / 簡易魚道 / 可搬魚道 / 遡上

Outline of Final Research Achievements

In this study, laboratory and field experiments were conducted using a steep stream-type fishway constructed and installed in the channel drop. In the laboratory channel was 100 cm wide while the field channel was 150 cm wide, therefor the unit width flow quantity was matched. The fishway width made the same; 24 cm and the flow quantity in the fishway was assumed to be the same quantity. As the results, even with a slope of 1/7, which is steeper than the recommended slope of 1/20 for the stream-type fishway, the water depth in the fishway was maintained, the flow velocity was reduced, and a variety of velocities were formed in the fishway. This is due to the within the steep stream-type fishway were devised the roughness. Thereby, the fish was able to become moving upstream of drop without difficulty.

Free Research Field

水工学

Academic Significance and Societal Importance of the Research Achievements

「魚ののぼりやすい川づくりの手引き」では，水路式魚道の縦断勾配を1/20以下にすることが推奨されている．一方，これは魚道延長が長くなりやすくなる特徴を示している．しかしながら，魚道延長が十分に確保できない箇所もあり，特に中小河川では，条件を満たすことが困難なときもある．本研究では，その推奨勾配より急な状況でも，魚類が遡上できるような水路式魚道内の粗度要素に工夫を施した．その結果，1/7の勾配であっても，魚類が無理なく遡上できることを示した．このことは，特に中小河川や小規模水路の落差部に魚道を設置する際に，非常に役立つ知見であるといえる．