Performance of a groyne in controlling flow, sediment and morphology around a tributary confluence

¹ Hosei University, 2-33 Ichigaya-Tamachi, Shinjuku, Tokyo 162-0843, Japan
² Tokyu Corporation, 5-6 Nanpeidaicho, Shibuya, Tokyo 150-8511, Japan
³ National Institute of Technology, Akashi College, Uozumi, Akashi 674-8501, Japan

^* Kohji Michioku: kohji.michioku.47@hosei.ac.jp

Abstract

In a middle stream reach, irreversible morphological changes are observed such as growth of a huge sandbar in front of the confluence, thalweg migration from the left to right bank, erosion of the main channel and sedimentary deposit on the floodplain. As a countermeasure against such degradation of river morphology, a groyne was constructed beneath the tributary confluence. Performance of a groyne in controlling flood flow, sediment transport and river morphology was investigated by a twodimensional hydrodynamic model. The analysis on twenty years of morphological change indicates that the groyne has an excellent performance in improving quality of river morphology such as reduction of the sandbar development and migration of the thalweg to the original position.