Improvement and limit of the flood reduction function of forest basin considered local forestry revival

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K06512
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Hydraulic engineering
• Research Institution: The University of Tokushima
• Principal Investigator: TAMURA Takao 徳島大学, 大学院社会産業理工学研究部(理工学域), 准教授 (40280466)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 森林 / 洪水低減機能 / 林業 / 流域治水 / 流出解析 / グリーンインフラ

Outline of Final Research Achievements

Hydrological measurement and run-off analysis were performed by Hashimoto forestry area (needle wide mixture multistratal forest). Flood reduction function of the forestry area was evaluated quantitatively and it was studied about improvement and limit of the flood reduced function in Nakagawa upstream forested region.
The rainfall insulation rate of the Hashimoto forestry area was 20%. A model guessed the flood reduced function to be bigger little than that in other forestry. The thickness of the surface ground layer and the size of the ground surface resistance are its cause. Needle wide mixture woods influence that. The outflow simulation which altered a coniferous forest in the Nagayasukuchi dam upstream region using the Hashimoto forestry system was caluculated. The flood case of typhoon 201411, a model estimated that it was possible to reduce the peak flood 7 %.

Free Research Field

水文学

Academic Significance and Societal Importance of the Research Achievements

今後の林業のモデルケースと見なされ，針広混交複層林・択伐式林業が営まれている橋本林業林地の洪水低減機能を水文観測と流出解析によって定量的に評価することができた．これはグリーンインフラとして注目されている森林を活用した流域治水を考える上で貴重な知見となる．また森林には木材生産や洪水低減機能など数多くの公益的機能があるが，その総合評価にも寄与できる．さらに地域林業という観点からは橋本氏のように積極的に取り組む林業家のモチベーションともなりうると考える．