Diversion flows from rivers or main channels affect bed morphology and cause erosion and sedimentation at the diversion channel junction. In a diversion channel flow system, the scour depth and scour length are considered important parameters and should be taken into account during the project construction stage because it affect the stability of main channel banks and crossing structures. In this study, the scour depth produced by diversion flow in a main channel was investigated using a physical sand bed model. The investigations considered five diversion angles (30°, 45°, 60°, 75°, and 90°), three bed width ratios (29%, 38%, and 48%), and five total discharges (7.25, 8.5, 9.75, 11, and 12.25 L/s). Results indicated that the scour depth in the main channel reduced as the diversion angle reduced. Empirical relationship to demonstrate relative scour depth (Kds) for different diversion angles and bed width ratios was proposed. Relative scour depth can be defined as a relative scour depth in case of a diversion angle of θ°to that with 90°for the same flow condition and bed width ratio. Empirical relationships to estimate the scour depth and scour length with the governing hydraulic parameters were also established with a good accuracy. Testing the proposed relationships gave reasonable mean errors of 3.46% and 10.3% in predicting scour depth and scour length, respectively.

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The work concerns a laboratory study to investigate the effect of changing the bed roughness of the main channel on the branching discharge and separation zone formed in the main channel as a result of discharging flow through a branch channel. The ratio of main channel roughness to the roughness of the branch channel bed has been changed between (1.7-3.9) for two branching angles (30˚, 90˚) and for different values of main channel discharge ranged between (7-17) L/sec. Laboratory result shows that branching discharge ratio increases by the increasing the total discharge through the main channel at roughness ratio less than (2), where's the branching discharge decreases at roughness ratio greater than (2), and stay constant at roughness ratio about (2) for all discharge passing through the main channel. The result shows that the length of the separation zone decrease with the increasing in the roughness ratio and total discharge through the main channel.

Diversion channels are used in irrigation networks and many of water resource projects. Due to the diversion of a portion of the water, a ratio of the main flow streamlines is deflected to the diversion channel (on the diversion side).The ratio of dividing streamlines increases from the surface to the bottom due to the high momentum of the flow upper layers, which resists its diversion. This negatively affects the quality of diversion water, as the largest proportion of it comes from the high sediment concentration of the lower layers. In this study, the effect of changing the sharp edge of the diversion channel entrance to a circular edge (at upstream, downstream or both sides) on the behavior of dividing streamlines. The study considered five different percentages of the diversion discharge ratio (between 7.5% and 30% of the total discharge) with five different diameters of the circular edge. The results indicated that there is a noticeable improvement of the dividing streamlines uniformity along the flow depth when using the upstream and downstream circular edge, as well as when using large diameter of the upstream circular edge only. In addition, increasing the discharge ratio reduces the regularity of the flow lines.

Accumulation of the sediment in the stream of the diversion channels adversely affects its operational systems. Diversion channels are often constructed perpendicular to the main river. In this study, the water flow and sediment transport in the diversion channel with different angles were investigated in an attempt to maximize water discharge and minimize sediment discharge. A physical model with movable bed was used to simulate water and sediment flow with five diversion angles (θ) between (30°-90°). Moreover, three bed width ratios (Br) (the relation between diversion to main channel bed width) between 30% and 50% and five total discharges between (7.25 L/s to 12.25 L/s) were considered for each case of (θ). The results showed, up to 10%, increasing in proportion discharge ratios for 30 and 45 diversion angles compared with 90° diversion angle. The results also showed that the lowest diversion sediment concentration was provided by the (θ) of 30°. Across all scenarios, the average proportion concentration reduction was 64%, compared with 90° diversion angle. Closer observation of the diversion system mechanism confirmed that decreased (θ) result in decreased sediment concentrations in the diversion channels. In conclusion, the diversion channel water and sediment discharge could be effectively managed by changing the (θ) to 30° or 45° instead of 90°.