空撮画像を用いたダム貯水池の流木捕捉量の推定手法の開発

抄録

One of the characteristics of the severe rainfall event in north Kyushu July 2017 was damages by a huge amount of driftwood deposited inside and outside the channel. We developed a method to quickly estimate the volume of driftwood accumulated in reservoirs using aerial photos taken at the Terauchi Dam. We automatically extracted woody pieces in the images based on color and brightness by using ImageJ. Our estimate of the volume of driftwood was almost equal to an actual volume of wood, which was removed from the reservoir a few months later of the event. Size and density of driftwood tended to be greater in the upstream than the downstream. The upstream section of the reservoir was shallow and narrow, which might have promoted a trapping effect of reservoir.