This research investigated the effect of sediment non-uniformity and clay content on reducing erosion downstream of labyrinth weirs. Experiments were conducted in a flume with a length of 12 m and a width of 80 cm. A labyrinth weir was made with an L/W ratio of 2 and two types ofsediments – namely uniform (S1) and non-uniform (S2) – with a median diameter of 2 mm. Moreover, 10 and 15% clay were added to each sediment type, and the experiments were performed at three discharge rates of 5, 10, and 15 l/s with a tailwater of 11 cm for 12 h. The scour rate was measured with a point gauge and plotted in SigmaPlot. The largest scouring occurred near the junction of the weir and the channel wall. Increasing clay by 10 and 15% reduced the scour depth by about 84 and 90% in S1 and 80 and 91% in S2, respectively. Therefore, the presence of clay in the sediment created more adhesion within soil particles, creating higher compaction, which led to a decrease in the scouring depth. In addition, by changing the sediment from S1 to S2, the non-uniform structure of S2 proved more effective in reducing scouring.
