[H-DS05] Landslides and related phenomena

[HDS05-09] Field monitoring of pore-water pressure in debris flow

*Fumitoshi Imaizumi¹, Shunsuke Oya², Shoki Takayama¹ (1.Faculty of Agriculture, Shizuoka University, 2.Nippon Koei Co., Ltd.)

Keywords:debris flow, pore-water pressure, field monitoring

Characteristics of debris flows are dependent on the pore-water pressure in debris flows, which sometime cause severe sediment disasters. Therefore, understanding of the pore-water pressure in debris flows is essential to improve debris flow mitigations. We have conducted field monitoring of pore-water pressure in debris flow at Ohya landslide scar, central Japan. Pore-water pressure in some partly saturated debris flow surges highly exceeded hydrostatic pressure of clean water. Depth gradient of the pore-water pressure, monitored by water pressure sensors at multiple depths, was clearly different among debris flow events and surges. The depth gradient of pore-water pressure in the lower part of partly saturated surges was higher than the hydrostatic pressure of clean water. Magnitude of flow and flow type (fully and partly saturated) are potential factors affecting the depth gradient of pore-water pressure. Travel distance of debris flows, which were investigated by periodical UAV-SfM (structure from motion using unmanned aerial vehicle) and monitoring of time lapse cameras, was not cleary related to the magnitude of pore-water puressure.