[H-DS29_28PO1] 湿潤変動帯の地質災害とその前兆

[HDS29-P02] 南アルプスにおける過去40年の大規模崩壊の発生状況と土砂生産

*西井 稜子¹、今泉 文寿² (1.筑波大学、2.静岡大学)

キーワード：大規模崩壊地, 土砂生産, 空中写真, 地理情報システム, 南アルプス

Many large landslides are distributed in the southern Japanese Alps which consists of high relief and steep slopes. A lot of sediments deposited in dams suggest that sediments are produced actively in upper streams. To evaluate the sediment supply from landslides, this study addressed the mapping of landslides (>10000 m²) in Ooi River and Hayakawa River (total area is 862 km²) using aerial photographs and orthophotographs in 1970s and 2000s (partly including 2010s). In addition, we computed the volume of sediment supply in several large landslides based on the difference between DEMs from LiDAR data in multiple shooting periods. One hundred eighty landslides were extracted from photographs in 2000s to 2010s. The comparison between the distribution maps of landslides in 1970s and 2000s indicated that an initial large landslide (>100000 m²) had not occurred since 1970s. In contrast, some landslides had enlarged gradually. Erosion rate computed from LiDAR data indicated the order of 10^-1 to 10^-2 m yr^-1. Such erosion rate suggests that the bare grounds after landslides are important as sediment supply area.