Author(s): Sumida Hideyuki; Muto Yasunori; Tamura Takao

Linked Author(s): Yasunori Muto

Keywords: Weir Removal; Flow Structure; Bed Evolution; Experiments; Secondary flow

Abstract: River crossing structures have contributed to flood control and irrigation. However, they adversely affect the river’s b iota and sediment transport. Recently methodology of full or partial removal of a weir in order to eliminate discontinuity of the river is under consideration. Nevertheless, impact on bed morphology and channel development due to the removal has not been fully explored. In this paper flume experiments were conducted to study effects of partial removal of a weir on bed morphology in its upstream. Detailed velocity measurements were conducted in order to clarify a mechanism of bed evolution process after the weir removal. The depth and width of the removed part were systematically changed. It is found that a channel formed from the removed part toward the upstream induces flow concentration and strongly affects cellular secondary flow structure after the removal. Velocity distributions in several cross-sections clearly shows that cellular secondary flow structure has close relation with sandbar formation. In addition shape of the channel near the weir, which is changed after the removal, is different in accordance with the removal shape. The shape is deemed to affect strongly the flow concentration, and eventually sandbar formation in a whole flume.

DOI:

Year: 2015