A Study on Mapping of Potentially Unstable and Shallow-Seated Landslide Slopes in the Hilly Mountainous Regions, Northeast Japan

点击翻译按钮获取中文摘要

The purpose of this study is to clarify the mapping method of potentially unstable slopes under heavy rainfall condition by using parameters related to the topography, geology and vegetation of actual shallow-seated landslides, and to discuss the relationships between the unstable areas and slope units.In granitoid areas, the Abukuma Mountains, the critical safety factors which distinguish between unstable and stable slopes are presented by both geologic and vegetational conditions, on the basis of the field observations and soil mechanical experiments. In consideration of the thickness of decomposed granite soils and the slope gradient, it becomes clear that the unstable areas are concealed partly in the upper valley-side slopes, especially in the uppermost parts of them, which are considered to be relatively stable in general. It is therefore necessary to study further the relationships between classification of slope units and the processes of slope evolution from the view of micro landform classification.On the other hand, surface landslides occur mainly in the lower valley-side slopes in the Neogene sedimentary rocks area, the Tomiya Hills. To make discrimination between the unstable and stable slopes in the Neogene areas should be discussed continuously as a future issue, because the critical state of the shallow-seated landslides occurring could not be currently revealed. In this regard, the landslide appearance and the changes of the soil moisture of valley-side slopes in the Neogene volcanic rocks area, the central highland of Kenya, could be made clear from the field survey and slope hydrological observations, where the topographical conditions are appreciably similar to those in the above-mentioned areas.