Author(s): Kazuki Karasawa; Kazuaki Ohtsuki; Rei Itsukushima And Tatsuro Sato

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Keywords: Transverse rib; Alluvial fan; River-channel sediment removal; Basin geology

Abstract: In Japan, large-scale sediment removal is undergone for climate change adaptation in the rivers of alluvial fans. The transverse ribs in such areas are important to the ecosystem and assist in riverbed protection, and no method has been proposed for channel-sediment removal that preserves this morphology. The ease of formation is expected to vary depending on the geology of a river basin. The objective of this study was to clarify the effects of channel-sediment removal and geology on the formation and renewal of transverse ribs within a period of one year. A wide range of transverse ribs and giant rocks were surveyed and compared using orthoimages generated from aerial photographs of rivers in the Fuji River system, Japan. The results showed that conglomerations are more likely to form in granite and andesite, and less likely to form in sedimentary rocks. Renewal of the transverse ribs was mainly observed in the 1/40–1/20 gradient zone. The influence of river-channel sediment removal was not as apparent, and the difference between those with and without sediment removal was indistinct compared to the results of other studies conducted in the same areas.

DOI: https://doi.org/10.64697/978-90-835589-7-4_41WC-P1796-cd

Year: 2025