Hydraulic structures, such as pile dikes, groins, splitting dikes, have been constructed in natural rivers to improve the channel stability to bank or bed erosions by reducing flow velocity or changing flow direction. In order to produce better river environments, river flow mechanisms with the hydraulic structures need to be intensively studied. In this paper, an experimental flow field with non-overflow groins in a straight rigid-boundary channel was produced, and the characteristics of the flow with groins positioned in stagger were also investigated by measuring two dimensional flow velocity fields. Eight different types of groins were positioned on the left side of the model channel. The velocity distributions around the groin and the geometry of bed flume before and after are measured. The effects of various groin parameters (width of groin per channel width, and its inclination) on the change in water velocity are studied. The model studies are performed using regular waves in a basin. The results show that the maximum water velocity was when the groin width was equal to one fifth of the flume width. The groin preferred to place inclined with 60° with the flume side.
Key words: Nature-oriented river works, open channel flow, meandering river, experimental works, open channel flow, coastal evolution.