2021 Fiscal Year Final Research Report

Development of a storm-runoff model based on the measurements of saturated-unsaturated flow on a hillslope.

Research Project

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Project/Area Number	19K04632
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	Lake Biwa Environmental Research Institute
Principal Investigator	Kojima Nagahiro 滋賀県琵琶湖環境科学研究センター, 総合解析部門, 専門員 (00503624)
Co-Investigator(Kenkyū-buntansha)	谷誠人間環境大学, 人間環境学部, 特任教授 (00314245) 佐山敬洋京都大学, 防災研究所, 准教授 (70402930) 正岡直也京都大学, 農学研究科, 特定助教 (90786568)
Project Period (FY)	2019-04-01 – 2022-03-31
Keywords	山地源流域 / 谷壁斜面 / 降雨流出応答 / 流出機構 / 鉛直浸透過程 / 土壌物理性 / 斜面モデル / 流出モデル
Outline of Final Research Achievements	Considering the importance of comprehensive flood control measures for watersheds from mountains to rivers, we observed soil moisture dynamics on a forested hillslope to develop a runoff model based on the dynamics. During a large storm event, the vertical propagation of pressure head occurred quickly in the downslope area, while the pressure head rise was small, remaining a dry condition, at the bottom of the soil layer in the upslope area. The temporal variations of pressure head at the layer bottom on the mid slope to lower slope corresponded to the variation of outflow rate observed at the slope toe, suggesting that the runoff response was mainly controlled by the vertical unsaturated flow process in the soil layer. This result was applied to the development of a distributed runoff model considering the soil moisture dynamics, contributing to an assessment of the effects of soil types on the river runoff.
Free Research Field	森林水文
Academic Significance and Societal Importance of the Research Achievements	本研究の成果によって、森林斜面における雨水浸透過程が鉛直不飽和浸透流をベースにした流出モデルで表されることが明らかになった。このことからこれまでの研究では得られなかった、流出応答に対する土壌物理性等の影響について評価できるものと推察された。また、実測を反映したシミュレーションモデルが得られ、森林の持つ水源涵養機能をより実態に即した評価ができる可能性が示され、さらには、山地から下流域までを対象にした流域総合治水対策に貢献できるものと考えられた。