| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1991: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1990: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
(1) Objective
This study aims to evaluate the surface runoff mechanism in the hillslope, and propose a conceptual model, according to the methods as follows,
1) quantification of soil properties relating to the soil moisture movement, by the aid of laboratory and field permeability tests
2) consideration of the conditions for surface and subsurface through the experiments using a ranfall simulator
3) tests and improvement of soil parameters and the conditions by a physically based numerical simulation model
(2) Approach
1) Various models for the soil properties expressed by the relationships between the water content (rheta), capillary head (psi), and hydraulic conductivity (K) are reviewed, and three models for deriving unsaturated conductivity-suction relationship from moisture-suction data are assessed by comparison with laboratory experiment. Also, a revised model to evaluate the saturated hydraulic conductivity based on the psi-rheta relationship is proposed.
2) A rainfall simulator, which is able to generate rainfall with the intensity of 20-250 mm/hr. The ability and applicability of this simulator are examined by the exper imen ts on vert ic al ra inf all inf i l trat ion. Also the conditions for the surface ponding and the air-entrapped infiltration are investigated.
3) Distribution of soil properties along the hillslope in the natural experimental basin is made clear by the laboratory tests, using small soil samples from the soil surface to the 200cm depth. Also, numerical simulations for the subsurface moisture behavior in the hillslope are carried out, based on the FEM model. As a result, the influence of initial conditions and distribution of soil properties on the variation of source area distributing to the surface runoff is grasped.
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