Abstract. Due to a typhoon and a stationary rain front, record amounts of rain fell in September 2011, and the largest class of discharge in recorded history was observed in the Otofuke River of eastern Hokkaido in Japan, and extensive bank erosion occurred in various parts of the river channel. Damages were especially serious in the middle reaches, where part of a dike was washed out. The results of a post-flood survey suggested that the direct cause of the dike breach was lateral advance of the bank erosion associated with the development of meandering channels. As the related development mechanism and predominant factors have not yet been clarified, this remains a priority from the viewpoint of disaster prevention. A past study on the development of meandering channels was reported by Shimizu et al. (1996). In this study, the meandering channel development process was reproduced using a slope failure model that linked bank erosion with bed changes. The study attempted to clarify the meandering development mechanism in the disaster and its predominant factors by using this model. The analysis properly reproduced the characteristics of the post-flood meandering waveforms. Therefore, it is suggested that the development of meandering during the flood attributed to the propagation of meandering downstream, which is triggered by the meandering flow from the meandering channel in the upstream, which also suggests that this propagated meandering then caused a gradual increase of meandering amplitude accompanied by bank erosion in the recession period of the flood.

In this study, we developed the vegetation prevalence model. This model takes into account the existence/nonexistence of vegetation and the resistance of willows above ground and their root systems to flowing water and sediment transport at different tree growth stages. The growth increment regarding various parts of a willow tree is estimated on the basis of the tree age. In the model, willows' resistance to flowing water and sediment transport is varied with time to simulate each growth stage. The vegetation prevalence model was incorporated into a riverbed evolution analysis model for analyzing the mechanism and the contributing factors of thick and extensive vegetation growth.

the largest discharge in recorded history was observed in Otofuke River, causing riverbank erosion in various parts of the basin. Damage was especially serious in the middle reaches, where part of a dike was completely washed out. The results of a survey suggested that the cause of the dike breakage was bank erosion associated with the development of a meandering channel. As the related development mechanism and predominant factors have not yet been clarified, this remains a priority for disaster prevention. In this study, the meandering-channel development process was reproduced using a slope failure model that linked bank erosion with bed fluctuations. The study attempted to clarify the meander development mechanism and predominant related factors based on this model.

Abstract. Due to a typhoon and a stationary rain front, record amounts of rain fell in September 2011, and the largest class of discharge in recorded history was observed in the Otofuke River of eastern Hokkaido in Japan, and extensive bank erosion occurred in various parts of the river channel. Damages were especially serious in the middle reaches, where part of a dike was washed out. The results of a post-flood survey suggested that the direct cause of the dike breach was lateral advance of the bank erosion associated with the development of meandering channels. As the related development mechanism and predominant factors have not yet been clarified, this remains a priority from the viewpoint of disaster prevention. A past study on the development of meandering channels was reported by Shimizu et al. In this study, the meandering channel development process was reproduced using a slope failure model that linked bank erosion with bed changes. The study attempted to clarify the meandering development mechanism in the disaster and it's predominant factors by using this model. The analysis properly reproduced the characteristics of the post-flood meandering waveforms. Therefore, it is suggested that the development of meandering during the flood attributed to the propagation of meandering to downstream, which is triggered by the meandering flow from the meandering channel in the upstream, and also suggested that this propagated meandering then caused a gradual increase of meandering amplitude accompanied by bank erosion in the recession period of the flood.