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 30m. 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.

Key wordsFLiDAR survey, DEM differences, sediment dynamics, earthquake, shallow landslides