抄録
New waterway projects such as cutoffs and gravel extractions have been carried out all over the country. The shortcuts have lowered river water surface elevation during flooding, and they have been shown to suppress these flooding events. On the other hand, the riverbed elevations rapidly decreased as bed slope changed artificially and canyons were formed in several rivers. Little is known about how riverbed degradation occurs or how the canyon is formed by change in the bed slope. In this study, we conducted numerical simulations to evaluate the deformations of alluvial bed and peat bed. The results suggest that the bed slope becomes constant on the alluvial bed and the erosion proceeds at the bare peat bed. The results also show that the upstream migration of the peat bed slope forms cyclic steps morphology. Also, we carried out numerical simulation to reproduce bed degradation of the Yubari River caused by cutoffs.
