UAV Observations for Soil Volume Estimation of Debris Flows

UAV (Unmanned aerial vehicle) observations were performed at damaged areas by heavy rain-induced debris flows in Hiroshima, Japan on August 2021. Digital surface models (DSM) and ortho-rectified images were developed from the UAV-derived aerial images. Scars of surface grounds in the mountains produced by the debris flows were clearly identified in the ortho images. Difference of elevations were calculated from the post-event UAV-based DSMs and pre-event DEMs. Soil volumes produced by the debris flows were estimated by aggregating the elevation changes in the eroded areas identified as scars in the ortho images. We revealed that the relationships between eroded areas of the debris flows and volumes obtained in this study agree with those of previous studies.