[H-DS08] Landslides and related phenomena

[HDS08-03] 4D LiDAR monitoring of debris flows in Ohya landslide, central Japan

*Tatsuki Kaneko¹, Tomoya Osada², Fumitoshi Imaizumi², Hideaki Takahashi³, Shoki Takayama² (1.Interfaculty Graduate School of Mountain Watershed, Shizuoka University , 2.Faculty of Agriculture, Shizuoka University , 3.Nippon Koei)

Keywords:LiDAR, Debris flow, Landslides, 3D point cloud data, Field monitoring

Development of effective countermeasures for debris flow disasters are required because of increasing in the frequency of debris flow disasters in recent years. Understanding of the debris flow characteristics, such as water levels, flow velocities, and sediment transfer, are needed to improve the countermeasures. Many of debris-flow observations have just obtained one- and two-dimensional data such as water levels and video camera images. However, because the 3D shape of a debris flow change rapidly with time, conventional methods have not been able to fully understand the flow characteristics of debris flows. Recent progress in the LiDAR technology possibly provides the 3D point cloud data of running debris flows. In this study, we have developed an automatic LiDAR measurement system to monitor debris flows. The measurement system was installed in Ohya landlide, central Japan, to clarify characteristics of debris flows. As a result, we succeeded in obtaining 3D point cloud data of running debris flows on August 3 and 14, 2023. Longitudinal and cross-sectional profiles of debris flows, which were clarified using the 3D point cloud data, showed that the flow morphology was different between saturated and unsaturated flows. In addition, backstepping deposition of sediment from head of the debris flow surge toward upper channel reaches was observed from temporal changes in the longitudinal profile of the 3D point cloud data.