In this study, we tried to assess the factors that could affect the landslides occurrence (slope angle, forest practice and precipitation) in the eight sub basins of catchment of Miyagawa Dam, Mie prefecture, Japan. Our findings are summarized as follows:1) Collapsed area ratio is proportional to mean slope angle. 2) In each sub basins, the collapsed area ratio is in proportion to collapsing possibility area ratio index (APhr (t)) that was derived from a prediction model of slope stability considering forest practice. 3) Collapsed area ratio has significant correlation with both daily maximum and hourly maximum precipitation in each observation period. 4) Based on these findings, a new model was proposed considering slope angle, forest practice conditions and precipitation. The model was successfully applied to predict the collapsed areas in the study basins for the last forty years.

Key wordsFlandslide, slope angle, deforestation, reforestation, precipitation, prediction model