Abstract
Abstract. To evaluate the frequency and distribution of landslides hazards over Japan, this study uses a probabilistic model based on multiple logistic regression analysis. Study particular concerns several important physical parameters such as hydraulic parameters, geographical parameters and the geological parameters which are considered to be influential in the occurrence of landslides. Sensitivity analysis confirmed that hydrological parameter (hydraulic gradient) is the most influential factor in the occurrence of landslides. Therefore, the hydraulic gradient is used as the main hydraulic parameter; dynamic factor which includes the effect of heavy rainfall and their return period. Using the constructed spatial data-sets, a multiple logistic regression model is applied and landslide hazard probability maps are produced showing the spatial-temporal distribution of landslide hazard probability over Japan. To represent the landslide hazard in different temporal scales, extreme precipitation in 5 years, 30 years, and 100 years return periods are used for the evaluation. The results show that the highest landslide hazard probability exists in the mountain ranges on the western side of Japan (Japan Sea side), including the Hida and Kiso, Iide and the Asahi mountainous range, the south side of Chugoku mountainous range, the south side of Kyusu mountainous and the Dewa mountainous range and the Hokuriku region. The developed landslide hazard probability maps in this study will assist authorities, policy makers and decision makers, who are responsible for infrastructural planning and development, as they can identify landslide-susceptible areas and thus decrease landslide damage through proper preparation.
Highlights
Landslides are the most dangerous natural hazard in the mountainous regions of Japan
The results of the probability model, the spatial distribution of landslide hazard probability based on rainfall induced infiltration condition, geographical conditions and geological formations of the area are portrayed on landslide hazard probability maps using Geographic Information System (ARC/INFO-GIS)
Landslide hazard probability according to the extreme precipitation for different return periods are highly important, because return period dictates the time frames and design guidelines for countermeasures and it show the order of priority in mitigation processes and financial fund allocations
Summary
Landslides are the most dangerous natural hazard in the mountainous regions of Japan. Heavy snowfalls and earthquakes, which are frequent events in Japan, are the leading causes increasing these damaging hazards. Torrential downpours within short time periods, and resultant excessive increases in groundwater levels, are conducive to extensive landslides during the heavy rainfall season (Okimura et al, 1985; Iida, 1999). Landslide hazard assessments have become a vital subject for authorities, as they can assess and predict landslide-susceptible areas and decrease landslide damage through proper preparation. It assists decision makers who are responsible for infrastructural development and environmental protection
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