At volcanic mountain slope, geomorphological change is caused by gully erosion according to volcaniclastic material. A purpose of this study is to clear the relationship between the development of valley profile and the hydrological effect of volcaniclastic material. Authors analyzed about drainage net works in river basins and stratifications made by pyroclastic flow units. The drainage net works develop under the effect of final infiltration rates of each volcaniclastic material. Distribution areas of volcaniclastic materials accord to hard layer with low infiltration in stratification. As a result, development of valley profile is changed by the buried valley including the volcaniclastic material with low infiltration.