Study on the spatial distribution of water flow path within the soil layer in mountainous hillslopes

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K06125
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 40010:Forest science-related
• Research Institution: Kyoto University
• Principal Investigator: Masaoka Naoya 京都大学, 農学研究科, 助教 (90786568)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 水みち / 排水構造 / 土壌透水性 / ゲルフパーミアメータ法

Outline of Final Research Achievements

High-density observation of water flow and soil permeability within the soil layer on mountain slopes revealed that highly permeable water channels existed within the soil layer and acted as preferential drainage channels during rainfall. The surface/subsurface topography was confirmed to affect the local increase in soil permeability. Specifically, it was assumed that soil washout occurs due to large soil water fluxes that occur at locations with large catchment areas and angles. Water channels with a series of highly permeable zones existed heterogeneously within the watershed and corresponded to the locations of past landslide scars, suggesting that the formation of water channels is closely related to the topographical development process.

Free Research Field

森林水文学、砂防学

Academic Significance and Societal Importance of the Research Achievements

山地斜面内の水みちによる排水機構について実斜面での検証が数多く行われてきたものの、観測の難しさから統一的な見解は得られていなかった。本研究では高密度の透水性計測と水流観測から局所的な水みちを特定する手法を確立したことで、水文学における降雨流出過程の研究に新たな潮流を生み出すものである。また空間的な透水性分布と地形との関係性を明らかにし、将来的に未観測流域の透水性分布予測を実現するための基礎的な知見を得た。これは既存の流出予測モデルを高精度化し、流域総合治水に大きな進化をもたらす可能性がある。