Author(s): Kazuki Karasawa; Kazuaki Ohtsuki; Rei Itsukushima And Tatsuro Sato
Linked Author(s): Kazuaki Ohtsuki, Tatsuro Sato
Keywords: Transverse rib Alluvial fan River channel management Basin-scale factor NbS
Abstract: In Japan, rivers in alluvial fans are undergoing large-scale channel excavation in response to climate change adaptation, but effective alternation techniques have yet to be proposed for nature-based solutions (NbS). Transverse ribs in this area are essential for ecosystem and riverbed protection. The ease of its formation is expected to vary depending on basin characteristics, especially geology, which controls sediment dynamics and flow regimes. This study aimed to clarify the effects of channel excavation and geology on the formation and renewal of transverse ribs within one year. Using orthogonal images generated from UAV photographs of the target reaches, a wide range of transverse ribs and gigantic rocks were monitored, and the results were compared statistically. The results show that transverse ribs are more likely to form in granite and andesite geology and less likely to form in accretionary geology. The renewal of the transverse ribs was mainly observed in the 1/60~1/20 gradient zone. The influence of river channel excavation was not statistically significant, and slight changes were found between a pair of datasets in 2023 and 2024 in the same areas.
Year: 2025