This study suggested landslide hazard mapping method in the Chugoku Region using analytic hierarchy process (AHP) method and geographic information system (GIS). A landslide hazard assessment system for landslides used here is based on landslide distributions of about 16,000 places in the Chugoku Region, Japan. We considered relationship between landslide distribution and factor of landslide hazard (elevation, slope angle, slope type, catchment degree, geology and vegetation). These relations are introduced to pairwise comparisons of factors in the AHP method. Landslide hazard rank is evaluated based on AHP. A landslide hazard map is created based on the landslide hazard rank of Ⅰ－Ⅴ. The landslide distributions are almost consistent with the landslide hazard rank. These results provide a practical method that will be useful for evaluating landslide hazards.
In areas hit by landslide, the fluctuation characteristics of the groundwater level may change. This study used Bayesian optimization to estimate the parameters of a groundwater level reproduction model under the assumption that they are time-varying coefficients. Then, we used parameter fluctuations and functions to evaluate how the groundwater level fluctuation characteristics changed over a specific analysis period. We applied this method to a landslide area where a groundwater drainage works were constructed, reproduced the groundwater level fluctuation, and evaluated the changes in the characteristics of the groundwater level fluctuation. Changes in groundwater level are shown to be accurately reproduced by varying each parameter. Furthermore, the tendency of parameter fluctuation indicated that the drop amount in groundwater level during no rainfall was increased after groundwater drainage works.
The Noneyama-kaido is an ancient road traversed from the east coast to the west coast of Muroto Peninsula, eastern Kochi Prefecture, Japan. The Tosa-han（Tosa domain）set the Iwasa checkpoint along with the road in the early Edo period. The remains of the Iwasa checkpoint are located on the ridge-top area ; however, the archaeological investigation has not been conducted until now. From the viewpoint of geomorphology and geology, there are many landscapes formed by gravitational slope deformation such as up-hill and down-hill facing scarps on ridges in and around the study area. In this study, we discussed the relationship between the location of the ruin and geomorphological process based on geomorphological interpretation of advanced topographic maps created from the data of the airborne laser survey system of the study area. The results show that the remains of the Iwasa checkpoint are located at flat surface with reasonable size on the ridge top shaped by toppling-type rock creep. In addition, the geological structure formed by rock creep zone made a reservoir of groundwater which was used as a resource of daily life water for local residents of the Iwasa checkpoint.