土砂災害危険区域の林地斜面における降雨の浸透過程の解明

抄録

Recently torrential downpours leading to sediment disasters have become more frequent and severe, which highlights the importance of advancement of the prediction methods of sediment disasters. In this study, as a first step towards the elucidation of the mechanisms of slope failures and debris flows, we conducted field observations and small scale experiments in the laboratory to reveal the rainfall infiltration and runoff processes on the forest slope of Mt. Takamatsu where debris flow occurred in August 2014. Field observation showed that at low intensity rains, the vertical infiltration downward from the ground surface occurred while at high intensity rains, the water movement in the upward direction was accompanied by a sharp rise in the pressure head in the deeper layer, whose value exceeded the actual ground water level. From the small scale experiment, it was confirmed that the pore water pressure of the lower layer increased in the similar way as the field observation.