Hydrologic properties in soil layer are determined by various kinds of heterogeneities (for example soil pipes, cracks, cobbles and forest roots etc.). And these heterogeneities give large influences to hydrologic processes in soil layer. Therefore, it is important to estimate accurately effects that heterogeneities give for water movement in soil layer. Nevertheless, few studies concerned with these phenomena, without soil pipes study. In this study, on hydrologic processes, that is, the movement of water in soil layer, in order to understand effects of forest roots (living]root and decayed]root) which are a portion in primary factor to make soil layer structure heterogeneous, laboratory flume experiment using a simplified form pseudo roots was carried out. The following matters were confirmed by this experiment.
1) Forest roots in soil layer increased runoff in a steady state.
2) Permeability of the entire flume is increased by presence of forest roots, when slope is at least20°.
3) The hydraulic property around forest roots is represented in the similar to Manning law.

Key wordsFheterogeneity, forest roots (living]root and decayed]root), hydrologic properties in forest soil, slope stability