The numerical analyses are carried out using a seepage-deformation coupled method for unsaturated soil (Oka et al., 2009). The analyses presented here are based on Biot's theory (Biot 1962) extended by the theory of porous media (Bowen 1976). Common constitutive and hydraulic parameters that represent the soils are employed in the simulations. The mechanism of the seepage flow direction and strain localization on the slope surface are discussed mainly with respect to the water permeability of the soil. From the numerical results, it was observed that the deformation of the embankment significantly depends on the water permeability of the soil and it is localized on the slope surface at the river side; the larger the water permeability of the soil, the larger the velocity of the seepage flow, and the larger the deformation on the surface of the river embankment.