降雨特性及び土質強度特性が表層崩壊発生場に与える影響について ～三重県宮川上流域を事例対象として～

抄録

Here we indicate a result of the effect of rainfall characteristics and soil strength on the potential for shallow landslides over large areas using a simplified physically based model. The model was based on 50-m grid digital elevation model of the Miyagawa upper river basin at Odai-cho, (a former Miyagawa village) in Mie prefecture. The model calculates the distribution of the shallow-infiltrated water level by Darcy's law and a safety factor estimated using infinite slope stability analysis for each 50-m grid cell. Response analysis of this model with a steady rainfall intensity showed that the area of the potential shallow landslide ratio increased with rainfall intensity, stabilizing at rainfall intensities of over 50 mm/hr. The spatial distribution of the potential shallow landslide area during steady rainfall was initially highest in the vicinity of the channel heads and hollows, expanding as one moved upstream. Response analysis using actual five heavy rainfall events data, revealed the potential for shallow landslide development decreased dramatically when apparent soil cohesion ranged between 3 to 9 kPa, indicating that the time rate change of the shallow landslide potential was specified by both temporal rainfall patterns and the value of apparent soil cohesion.