Author(s): Ryotaro Endo; Takao Tamura; Yasunori Muto

Linked Author(s): Yasunori Muto

Keywords: Alternate bar; Fixation; Groyne; Riverbed

Abstract: In recent years, the Nakagawa River in Tokushima Prefecture, Japan has been facing a fixation of meandering river channels. As a result, increasing bar elevation and deepening thalweg have become problems. Riverbed degradation and vegetation encroachment are severe environmental issues in many Japanese rivers due to in-channel sediment shortage by past over-exploitation of sediment and upstream dam constructions. Measures of river restoration that are effective in such sediment deficit conditions are required. Therefore, in this study, an experiment is conducted to solve the fixation of alternate bars. First, the effects of the width and height of the flood plain on the meandering river channel were investigated. And, the effects of different flow section shapes on the river channel were studied. As a result of the experiment, widening the flood plain width may prevent the deepening and increasing bar elevation of meandering river channel. It was also found that single flow may be able to eliminate fixation of the bar. However, compound flow can reduce the deepening and increasing bar elevation. It was found that the problem could not be solved only by installing the flood plain. Second, impermeable groynes were installed in addition to the flood plain to promote the destruction of the fixation of alternate bars. For the groynes, impermeable models were tested by varying the discharge. The effects of the different discharge on the riverbed will be considered. It was found that one impermeable groyne did not eliminate the fixation of the bar.

DOI: https://doi.org/10.1007/978-981-97-6009-1_10

Year: 2022