Author(s): Shigeru Mizugaki; Takuya Inoue; Susumu Yamaguchi
Linked Author(s):
Keywords: Sediment disaster; Alluvial fan; Flume experiment; Particle size; SfM-MVS
Abstract: Recent climate change had brought flood and sediment disasters in Hokkaido, northern Japan. Especially in August 2016, the four typhoons and associated heavy rain caused the catastrophic disasters by the debris flow, bank erosion, flood and sedimentation at many towns located in the foot of alluvial fans. To elucidate the mechanisms of these sediment disasters and impact of sediment supply from mountain area on river morphology downstream in alluvial fan, the flume experiment was conducted using plastic media color-coded by size. Variation in morphological change and particle size on the ground surface among the cases were investigated by photo survey followed by 3D modeling using SfM-MVS, GIS and hydraulic simulation. Particle size information obviously showed the sedimentation of coarser particles aggraded the bed and caused the bank erosion and flood over. Meanwhile, the bed of thalweg was found to be consist of finer particles, which clog and flatten the bed, making the larger particle easily to be transported. Four cases on account of different volumes of sediment supply and same discharge showed that the increase in sediment supply could cause the sediment flooding and be meandering upstream. These results well represented the geomorphic features after the sediment disaster occurred in August 2016 at the Pekerebetsu River, suggesting that this experimental apparatus can be available to learn the mechanisms of river morphodynamics and disasters in the alluvial fan.
Year: 2018