鹿児島大学附属高隈演習林における2016年9月の豪雨による侵食・崩壊の形態と生産土砂量

抄録

  The Takakuma Experimental Forest at Kagoshima University experienced record rainfall in September 2016. Following this event, we investigated sediment yields related to various types of erosion and collapse along forest roads and slopes within this forest. In particular, we focused on a 6.8-km² study area. To evaluate the effect of rainfall intensity on erosion and collapse, we compared results from September 2016 (when maximum hourly rainfall was 154 mm.) with those from September 2005 (when maximum hourly rainfall was 55 mm). The numbers of forest roads and natural slopes damaged by erosion and collapse in September 2016 were greater than in September 2005. Moreover, when erosion and collapse were of the same type, sediment yields recorded in September 2016 were between 1.4 and 11.5 times greater than in September 2005. Thus, total sediment yield in September 2016 was about 3.1 times greater than in September 2005. Our results suggest that both frequency and magnitude of erosion and collapse are correlated with rainfall intensity in this area.