In the Kii Mountains, deep-seated landslides have repeatedly occurred in the past. To develop a policy for the prevention of deep-seated landslides in this area, the volume and frequency of occurrence of landslides need to be measured. Although the age of landslides and debris flows have been actively studied, such as by using radio-carbon dating, tephrochronology, and dendrochronology, only a few studies have focused on the age of the deep-seated landslides. This study aims to estimate the age and frequency of deep-seated landslides in the Kii Mountains. Through geographical interpretation using aerial laser survey data, 19 slopes were selected for obtaining the samples by extracting the sedimentary terraces adjacent to the site of the deep-seated landslide. Based on the radiocarbon dating results of 42 samples, the relationship between the clarity of shape of the sliding cliff and radiocarbon dating was considered, and the frequency of deep-seated landslides in the Kii Mountains was examined.

Sabo soil-cement have some advantages of reducing the amount of sediment transported, reducing costs by using local sediment, and the construction method considers zero emission in the environment. The strength evaluation can be decided on a compressive strength obtained from a uniaxial compression test. However, the evaluation isn't conducted about dynamic load evaluation like a bouldery debris flow. The study conducts an impact loading experiment against Sabo soil-cement specimen to examine an impact resistance. In addition, in order to study an impact resistance possessed by the Sabo soil-cement, the relationship between a dropping weight accumulation energy and a collapsed volume and the relationship between dropping weight energy and compressive strength were summarized. In these results, the larger the compressive strength become, the larger the accumulated weight energy become. Also, the relationship between maximum impact load and weight energy increases linearly until cracks in the specimen. Therefore, if the compressive strength of the Sabo soil-cement is large, the Sabo soil-cement has large impact resistance against impact load on the collision surface.

In this paper, various factors such as landform and geological characteristics were analyzed with relevant digital data maps for the slope failures that were caused by heavy rainfall in the event of Typhoon No. 12 in 2011. By using 50 m x 50 m mesh GIS data, a total of 213 slope failures were analyzed by highlighting the hit rate with reference to various factors such as catchment area, slope angle, geology, landslide, terrain curvature and vegetation. A few characteristic features were manifested ; e. g., area at the geological boundary between igneous rock and sedimentary rock shows a high risk of slope failure. Based on the results of the factor analysis, a slope failure risk map was created using GIS data effectively. Using this risk map, the extraction and use of danger areas of disasters including debris flow were verified.