2023 Fiscal Year Final Research Report

Examination of mechanical behavior of debris flow and establishment of flood control techniques using abolished small earth dams

Research Project

PDF

Project/Area Number	21H02306
Research Category	Grant-in-Aid for Scientific Research (B)
Allocation Type	Single-year Grants
Section	一般
Review Section	Basic Section 41030:Rural environmental engineering and planning-related
Research Institution	Kobe University
Principal Investigator	Sawada Yutaka 神戸大学, 農学研究科, 准教授 (60631629)
Co-Investigator(Kenkyū-buntansha)	中澤博志静岡理工科大学, 理工学部, 教授 (20328561) 竹川尚希国立研究開発法人産業技術総合研究所, 計量標準総合センター, 研究員 (20828157) 小野耕平愛媛大学, 理工学研究科(工学系), 講師 (30804166)
Project Period (FY)	2021-04-01 – 2024-03-31
Keywords	ため池 / 廃止ため池 / 土石流 / 模型実験
Outline of Final Research Achievements	In this study, model tests reproducing debris-flow entering reservoirs and abolished reservoirs were conducted to verify the energy dissipation of debris-flow and to propose a reduction method of disasters by debris-flow using abolished small earth dams. As a result, it was revealed that the storage of water had the effect of reducing the impact on the embankment and the overflow of granular materials. On the contrary, when the volume of the debris-flow is large in relation to the water elevation, it was shown that high solitary wave can be generated. Although the bottom up of the V-shaped excavation of the embankment was found to be effective in controlling the discharge of granular materials, it was not effective in controlling driftwood discharge. Furthermore, although the storage of water upstream of the excavated embankment was found to be effective in terms of controlling the discharge of driftwood, it indicated the extension of the discharge area and the possibility of overflow.
Free Research Field	地域環境工学
Academic Significance and Societal Importance of the Research Achievements	気候変動により土砂災害が頻発化する中，ため池への土石流流入により深刻な被害が後を絶たず，リスク低減の観点から利用されなくなったため池の廃止が増えていた．一方，過去の豪雨では，上流からの土砂がため池に一時的に貯留された事例も報告されており，ため池の廃止により治水機能が低下するとの指摘もあった．このような背景の中，当研究課題では，貯水されたため池内に土石流が流入した場合の土石流の挙動解明と貯留水が土石流を減勢する効果について検証するとともに廃止ため池による土石流災害の減少方法について提案していることから，本研究成果は，ため池の廃止やその方法を検討する際の重要な知見を与えると考えられる．