Author(s): Koichiro Ohgushi; Wataru Kawahara; Toshihiro Morita; Maya Amalia Achyadi
Linked Author(s): Koichiro Ohgushi
Keywords: Chikugo River; Old meandering; Tributaries; River transportation; Fresh water intake
Abstract: Chikugo River is the largest river in Kyushu Island, Japan. This river has many cut-off channels nowadays but there are many old meandering waterways still existing. All inflowing tributaries into Chikugo River do not connect directly to main stream of present Chikugo River but inflow into the old meandering waterway of this river. In this study, the reason is considered hydraulically why all tributaries inflow into the old meandering waterway. Open channel flow analysis of the lower part of Chikugo River, and its tributaries, such as Shozu River, Kiritohshi River and Iryu River with a large meandering old river are implemented. A synergy effect of old large meandering of Chikugo River and inflowing tributaries is hydraulically studied to investigate the relationship between the old meandering of Chikugo River and the inflowing tributaries. As a result, developments of river transportation and fresh water intakes in this area are considered to be the main reasons for this situation. Cut-off channels can have increased the capacity of flow rate of Chikugo River but direct connecting between the cut-off channel of Chikugo River and its tributaries can increase the water level fluctuation range of the tributaries and has a negative influence on the river transportation and traditional fresh water intake. The old large meanderings are considered to be used for solving these problems considering a large tidal range of the Ariake Sea.
Year: 2018