The flow fields over a trapezoidal labyrinth weir (two-cycle) and a piano key weir were simulated using Flow3D, studying the impact of each model on the flow field in the weirs and the coefficient of discharge in comparison with the available experimental data. Moreover, the models were investigated experimentally in a 12.5 m long, 0.3 m wide, and 0.4 m high rectangular flume under clear-water conditions. The results showed good agreement between the data from the numerical and experimental models. The piano key weirs had a higher coefficient of discharged compared with labyrinth weirs. The coefficient of discharge was observed to increase by 26 percent as the height of the PKW was increased by 50 percent (from 5 to 7.5 cm). This increase was 24 percent for labyrinth weirs.