Linear depressions on mountain slopes have been considered a typical topographic feature reflecting gravitational deformation of the mountain mass. Although many studies have examined their formation processes, topographic controls on the development of the linear depressions have not yet been adequately clarified. This study investigated the major topographic factors characterizing stream catchments with linear depressions in the Kiso Mountains, central Japan, by a regression tree analysis. The results showed that the important topographic factors were a steep gradient, in particular, steep slopes flanking deeply incised trunk valleys, and large relief. Thus, the removal of material from the lower part of a slope in association with trunk stream incision probably destabilizes the interfluve slopes and promotes the development of linear depressions.

Residual strength of weathered rocks at slip surface zone is an important parameter for evaluating reactivation potential and understanding progressive failure mechanism. The combination study such as the soil residual strength, micro landform measurement, mapping and 3 dimensional safety ratio calculations lead the changing process of landslide risk. In this study, a series of experimentation have been performed with soils sample in humid tropical region from apparent slip surface at landslides along the Ho Chi Minh route in the Central Vietnam. The residual strength was measured using a Bishop-type ring shear tester at drainage condition. The soil hardness is examined by Yamanaka-type hardness tester at the sites. The grain size test, liquid limit test, plastic limit test, X-ray diffraction analysis and box shear tests were carried at laboratory. The data from study showed less hardness points at the around the slip surfaces. The mineral composition and physical characteristics differ depending on the geologic age, degrees of weathering and that their residual strength changes similarly. Especially, younger strata have a smaller angle of residual shearing resistance. The kaolin appears at heavily weathered rock instead of illite only contained in fresh rock. High-plasticity clays with high clay content, high plasticity index, and high liquid limit have a smaller angle of residual shearing resistance and that soils of young geologic age contain swellable clay minerals and produce high-plasticity clays.

In this research, after dealing with the handling of topographic terms in high-school Geography A textbooks, we examined the practicality of the usage frequency of these terms and their application to other units. The Geography A textbooks of the current course explain several terms related to landform; however, the descriptions often explain the concepts of terms and terrain, irrespective of the frequency of appearance. In Geography A, the relationship with everyday life is considered to be crucial to limit the number of terms used and explanations as well as reduce the number of terms to be learned. To develop a system that learns the mechanism of the topographic phenomena, it is necessary to review the whole person. In addition, the frequency of the usage of the terms learned by the terrain unit in other units of the later stage is considerably low. Therefore, a need exists to reconsider the unit structure, which is largely based on cooperation with other units. In the disaster prevention unit, the description that the topographical learning is relatively earlier than the other units is active is given. However, among them, insufficient points, such as a sudden increase of the new terminology, which did not appear in the topographic unit, and the invisible mechanism of the disaster phenomenon, can be observed. To protect ourselves from disasters and enhance disaster prevention awareness, it is essential to obtain the minimum necessary natural scientific knowledge using Geography A. As long as the contents to be learned are included in traditional memorization learning, the interest in learning as a geography itself/learning motivation may decrease. In practice, it is currently not feasible to revise the guidelines for teaching; however, in the future, it is anticipated that it will become a more practical course by reviewing how to comprehensively learn geography.

The report is considering that total management flow should be set at the fact finding and mapping stage, the risk evaluation stage, the categorizing stage, and at the management strategy set up stage. To assist investors (departments in charge of disaster prevention) and the engineer easy make an accurate and effective decision for selection the measures to responding to landslide disaster occur along the artery such as national road, it is necessary to build a total management system of landslides disaster risks. Especially in Vietnam, where the latest technical knowledge is not always reflected in the event of a landslide disaster outbreak in response procedures of departments in charge of disaster prevention. This study coordinate various processes from evaluation of landslide disaster risks on and along roads through simulation of landslide occurrence to proposal of a concept of countermeasures and monitoring into one work flow, to indicates a procedure to be conducted on each phase, and finally to propose a management system. For those purposes, the AHP hazard prediction method of reactivation risks of landslide topography to management classification is applied. The Japanese inspection sheet for landslide AHP score calculation is modified into more user-friendly representations for on-site use. In additionally, the landslide scale, spatial relation with a road and gradient of slopes is examined comprehensively to calibrate the landslide risk score. Based on the final landslide risk score, disaster vulnerability is set in descending order from level 1 to level 4, which corresponding to four levels of strategies of road maintenance: 4, countermeasures immediately; 3, tracking tools; 2, patrol incentives; and 1, regular patrols.