Characteristics of meandering streams after construction of the straight low-water channel in the Otofuke River.

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Satomi Yamaguchi, Jungo Funaki

Tuesday 30 june 2015

12:51 - 12:54h at Oceania (level 0)

Themes: (T) Sediment management and morphodynamics, (ST) River morphodynamics, Poster pitches

Parallel session: Poster pitches: 5B. Sediment - River

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The Otofuke River is one of the tributaries of the Tokachi River located in the eastern part of Hokkaido, Japan. Development of meandering streams in bank erodible channels has been observed in the Otofuke River since the construction of straight low-water-channel in 1975, in contrast to a braided streams which was the typical bed configuration of the river before. In 2011, extensive bank erosions occurred in various parts of the river channel, and a part of the dike was washed out during a flood. The amplitude of meandering streams were developed throughout the river, and chute cut-off were also occurred in a few part of the river at that time. In this study, numerical experiments with a field-scale channel were performed in order to reproduce the characteristics of the development process of meandering streams observed in the Otofuke River after the straight low-water-channel was constructed in 1975. It is found that meandering streams caused by alternate bar formation can be appeared in widening process of low-water-channel with local bank erosion at scouring points, and the local bank erosion is going rapid extremely in that process. The numerical experiments also suggest that the meandering streams can be changed to the braided streams after the low-water-channel widened to a certain extent. The transition process from meandering streams to braiding are appeared after the widening process of low-water-channel with meandering streams. The chute cut-off are seen to be occurred in the transition process to braiding. Propagating of the chute channel that cut the inner bank of meandering streams can be found in the that process. The channel development characteristics simulated in this study can be thought to show the basic process of the recurrent of braided channel observed in the Otofuke River before.