Ken'ichirou Kosugi

Abstract: Many models for soil water retention have been proposed. However, most of these models are curve-fitting equations and do not emphasize the physical significance of their empirical parameters. A new retention model that exhibits increased flexibility was developed by applying three-parameter lognormal distribution laws to the pore radius distribution function ƒ(r) and to the water capacity function, which was taken to be the pore capillary pressure distribution function ƒ(ψ). This model contains three parameters that are closely related to the statistics of ƒ(ψ): the bubbling pressure ψc, the mode ψ0 of ƒ(ψ) and the standard deviation σ of transformed ƒ(ψ). By comparison of this model with three existing models (the van Genuchten model, the Brooks-Corey model, and the modified Tani model), it was shown that ψc, ψ0, and σ are all essential for a general retention model.

TL;DR: In this paper, a review of previous field studies of pipeflow hydrology on forested steep hillslopes is presented, showing that the role of pipe flow in the storm runoff generation processes demonstrated two roles: the concentration of water and the rapid drainage to downslopes.

TL;DR: In this paper, a general conductivity model for unsaturated soils with lognormal pore-size distribution based on the Mualem-Dagan porescale model was developed.

TL;DR: In this paper, the authors conducted hydrometric observations using soil and bedrock tensiometers combined with hydrochemical measurements and water budget analyses at three different spatial scales to clarify water infiltration and redistribution processes between soil and shallow bedrock and their effect on storm and base flow discharge processes in a small headwater catchment underlain by weathered granite.