The Diyala River is considered the third most important river in Iraq. However, in the recent period, Diyala Governorate has been subject to several floods. This study aims to simulate an efficient labyrinth weir at the flood escape entrance branching from the Diyala River to reach the best entrance through which the flood waves can pass safely. The discharge coefficient was calculated laboratory for five types of trapezoidal side labyrinth weirs with different sidewall angles. Results showed that the coefficient discharge for the trapezoidal labyrinth side weir with an angle of the sidewall is 75ᵒ and has a discharge coefficient greater than the rest of the labyrinth side weirs. The second part of this study is validating the laboratory work using the CFD technique, where the same laboratory channel was simulated with the weirs of the side trapezoidal labyrinth using the Ansys-Fluent program. The numerical study gave very close results compared with the experimental results with MSE, where the error percentage error was from 3.3% to 10%. The last part of the work is numerically simulating the trapezoidal labyrinth side weir with an angle of the sidewall of 75ᵒ at the flood escape entrance branching from the Diyala River. The results showed that the side labyrinth weir has a larger discharge capacity of 4.8% than the rest of the traditional weirs and is more effective in flood treatment.
