It has been thought that cultivated terrace paddy fields on the landslide clod or the slope in the hilly mountainous area play the role of land conservation, such as the retention of the rain outflow. However, a detail of such a role is not yet clear. Since the abandoned terrace paddy fields increase due to a progress of recent depopulation, it is desirable to evaluate such a role in consideration of land use diversification. However, there exist very few studies which investigated and analyzed the changes of physical property and the water balance due to cultivation abandonment of terrace paddy fields from the viewpoint of infiltration. Therefore, the authors investigated physical property and water balance of cultivated and abandoned terrace paddy fields at the irrigation and non�]irrigation periods, and at the heavy rainfall, for the purpose of revealing the effect of cultivated terrace paddy fields on the land conservation. As a result, it was comprehended that surface soil of abandoned terrace paddy field increases in permeability and decreases in water retentivity slightly, while the grain size distribution is unchanged. And it was also turned out that the maintenance of terrace paddy fields as cultivated land has a possibility of temporal suppress of the groundwater level rising at the time of heavy rainfall, although it could lead the rise of groundwater level in the long�]run.

Key words�Fterrace paddy fields, permeability, infiltration, rainfall, water balance