粗粒な未固結堆積物かさ密度測定のためのフィールドSfM-MVS法 　　　　　　　－ヒル谷観測流域での調査－

抄録

The advent of high-resolution and high-accuracy DEMs from photogrammetry and LiDAR is providing an invaluable tool to measure erosion/deposition. At this resolution, it is thus now essential to take into account soils' bulk density variations. From a set of experiments in the Hiru-dani experimental watershed, the authors propose a SfM-MVS method to measure soil density. From a set of photographs prior-and post-excavation, we can calculate the volume and measure the mass of the material, deriving bulk-density and other geotechnical parameters. The method has two main strengths : (1) it allows for site-specific error analysis and (2) it works on unconsolidated heterometric material. In the Hiru-dani, the bulk density of the eroded bedrock was twice the one of the forest soil and 0.4 higher than the debris-flow deposit, showing that comparing DEMs is not sufficient to precisely account for soil loss erosion, or define the volume that was transported away from the catchment.