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Based on experimental measurements and observations in a laboratory channel, the hydrodynamic behaviour of the approaching flow and the amount of sediment entering a right-angled lateral intake in a diversion dam were investigated. The velocity field, both upstream of the intake in the main channel and in front of the intake in the sluiceway, were measured under various discharge combinations of the river, intake and sluice gate. In addition, velocity profiles both upstream and downstream of the intake and the amount of sediment entering it were measured. Analysis of the velocity data showed that the discharge of the sluice gate played an important role in determining the velocity profile and also the mechanism of sediment entry. All velocity profiles where the sluice gate was closed had an inflection point, where the flow direction changed, leading to a return velocity near the bed. The elevation of this point was a function of the intake discharge and approximately equal to the height of the entrance sill. Experimental observation showed that sediment entered the intake by a tornado-like vortex. The strength and frequency of the vortices depended on the intake and sluice gate discharges. Analysis of the sedimentation data showed that the amount of sediment entering the intake increased with increasing intake discharge. In addition, an increase in the sluice gate discharge caused an increase of sediment entry to the intake under the same intake discharge.

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This paper reports on a set of laboratory experiments involving a layout that is common in irrigation diversion works. The layout involves a lateral intake channel with a diversion dam, positioned to allow the flow to be controlled and managed. Based on experimental measurements and observations, the effect of diversion angle (ranging from 90 to 120°) on the structure of the approaching flow to the lateral intake and amount of sediment entering the intake was investigated. Velocity fields both upstream of the intake in the main channel and in front of the intake in the sluiceway were measured under various discharge combinations of the river, intake and sluice gate. Analysis of sediment measurements showed that the intake with a diversion angle of 110° had the least amount of sediment entering the intake. Analysis of the streamlines in the main channel showed that the width of the bottom-diverted current in the main channel decreased as the diversion angle increased. Furthermore, analysis of the data showed that the product of the width of the diverted current and the mean shear stress decreased when the diversion angle increased from 90 to 110° before increasing again at 120°.