Rainfall thresholds for shallow landsliding derived from pressure-head monitoring: cases with permeable and impermeable bedrocks in Boso Peninsula, Japan

摘要

Rainfall thresholds for shallow landslide initiation were determined for hillslopes with twotypes of bedrock, permeable sandstone and impermeable mudstone, in the Boso Peninsula,Japan. The pressure-head response to rainfall was monitored above a slip scarp due toearlier landslides. Multiple regression analysis estimated the rainfall thresholds for landslidingfrom the relation between the magnitude of the rainfall event and slope instability caused bythe increased pressure heads. The thresholds were expressed as critical combinations ofrainfall intensity and duration, incorporating the geotechnical properties of the hillslopematerials and also the slope hydrological processes. The permeable sandstone hillslope has agreater critical rainfall and hence a longer recurrence interval than the impermeable mudstonehillslope. This implies a lower potential for landsliding in sandstone hillslopes, correspondingto lower landslide activity.