In September 2005 a prolonged period of intensive rainfall caused landslides in the 27.48 km2 combined catchment area of the Byutano, Kataino and Sakaino rivers of Wanitsuka Mountain, Miyazaki Prefecture, southern Kyushu, Japan. The landslides began as deep]seated debris slides and developed into debris avalanches and debris flows that impacted upon downstream areas. Based on the potential for such events to occur again in this area, evaluations of the spatial and temporal distribution of landslides and slope geomorphological processes are crucial for assessments of hazard levels. Evaluations were based on inventory maps for the years 1948, 1974 and 2005. Interpretation of landslide patterns indicated that large landslides in the study area were preceded by creep deformation of weathered rocks, which controlled chronic landsliding. Approximately 34%of the catchment areas retain the potential to produce landslides. Within creep deformation areas in one catchment, the sites of most potential for triggering in the near future were identified based on geomorphological signatures. Past landslide triggering scenarios were also identified. Previous landslide occurrences in the three locations were established using 14C dating, with estimated ages ranging 200|3300 year BP.

Key wordsFdeep]seated landslide, Shimanto Supergroup, creep area, potential landslide site