抄録
The Mid Niigata prefecture Earthquake (M=6.8) that occurred on 23 October 2004 caused numerous number of landslides and landslide dams in the Imo River basin (A=38 km2) in Niigata Prefecture, Japan, altering sediment yield and discharge processes. Especially, a landslide that occurred in the Higashi-Takezawa district formed a large dam that reached as high as 30 m. Snowmelt and rain events produced more landslides in the river basin in the following years. We conducted multi-temporal aerial and terrestrial LiDAR surveys to clarify the post-seismic sediment dynamics in this seismically disturbed mountainous watershed. The surveys revealed the following : 1) The total amount of post-seismic sediment discharge obtained by multi-temporal bathymetric surveys coincided fairly well with that of the post-seismic sediment runoff, as revealed by the multi-temporal aerial LiDAR surveys. 2) The gully erosion and very small-scale collapses caused by snowmelt or snowcover could be detected by the multi-temporal terrestrial LiDAR surveys.
