1986 Fiscal Year Final Research Report Summary
Basic Research on the Prime Runoff Process of Rainfall in a Hillside Slope
| Project/Area Number |
59420043
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
農業土木
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| Research Institution | Kyoto University |
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Principal Investigator |
OKA Taro Disas. Prev. Res. Inst., Kyoto Univ. Associate Professor, 防災研究所, 助教授 (90027243)
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| Co-Investigator(Kenkyū-buntansha) |
TANAKAMARU Haruya Disas. Prev. Res. Inst., Kyoto Univ., Instructor, 防災研究所, 助手 (80171809)
MASUMOTO Takao Disas. Prev. Res. Inst., Kyoto Univ., Instructor, 防災研究所, 助手 (80165729)
MITSUTA Yasushi Disas. Prev. Res. Inst., Kyoto Univ., Professor, 防災研究所, 教授 (90027219)
KADOYA Mutsumi Disas. Prev. Res. Inst., Kyoto Univ. Professor, 防災研究所, 教授 (00027210)
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| Project Period (FY) |
1984 – 1986
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| Keywords | Hydrological cycle / Rainfall runoff / Soil moisture / Evaporation / Lysimeter / Macropores / 浸透能 |
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| Research Abstract |
1. The Runoff Process of Rainfall in Bare Slope
The process of evaporation, rainfall infiltration, surface and groundwater runoff have been basically investigated in connection with soil moisture movement using the slope lysimeter equipments.
First, the energy budget techniques have been used for determining evaporation from the bare slope of lysimeter. Next, the soil moisture movement were calculated numerically using the evaporation and rainfall as boundary conditions of soil surface. On the basis of the calculated results, the relationships between soil moisture movement and surface runoff, re-distributions of soil moisture and groundwater runoff were discussed.
2. Rainfall Infiltration in a Hillside Slope
The presence of large continuous openings (macropores) such as cracks and holes of differing sizes caused by desiccation, tiny animals in the soil and the rotting of roots, affects the infiltration of rainwater to soil.
In order to clarify the relations between rainfall infiltration ph
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enomena and macropores, infiltration tests and a soil survey made on the slope of a hilly region. These results indicate that the infiltration rate of rainfall decreased rapidly after rain began, and that the final infiltration rate too large for the prevailing soil character.
Based on the results, a simulation method was established and investigated. First, the amount of rainfall infiltrating soil containing fine macropores was calculated from a model that combined viscous flow within the capillary tubes and unsaturated soil water flow. These calculations showed that fine macropores increase the hydraulic conductivity of the 5-10 fold. Next, the amount of rainfall infiltrating soil containing coarse macropores was calculated based on the following assumptions: (a) The coarse macropores were filled with coarse, porous material of high hydraulic conductivity. (b) The soil around these coarse macropores was uniform and homogenerous. The calculated results agree well with the infiltration curve obtained from field tests. Less
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