2022年と1967年に新潟県村上市で発生した豪雨による表層崩壊の比較 －山地崩壊に免疫性はあるのか－

抄録

It has been noted the “immunity of landslides”, which means landslides are less likely to occur on landslide experienced slopes, but it has not yet been clarified. To reveal the immunity of landslides, the spatial distribution and characteristics of shallow landslides caused by heavy rainfall in 1967 and 2022 in the Murakami City, Niigata Prefecture were analyzed. The results showed that only 20% of the 2022 landslides overlapped with the 1967 landslides. The soil in the 1967 landslides area had developed only about 10 cm in 55 years, which is insufficient to destabilize the slopes and cause new landslides. The 2022 landslides occurred on landslide-prone slopes that did not experience landslides due to heavy rainfall in 1967. These results indicate that the immunity of landslide is exerted at least for 55 years on the landslide occurred point. However, if areas with high potential for landslide occurrences remain within a watershed, immunity of landslide at the watershed scale is not expected.