AbstractPooled stepped chutes with openings as a design requirement are associated with high flow transmission efficiency and smaller downstream dissipation structures; however, these design openings may negatively affect flow characteristics. In this study, 3D numerical simulations were conducted on large pooled stepped chutes equipped with openings and different pool heights, which benefited from the volume of fluid (VOF) method, to track free-surface configuration, and the use of the k−ε(RNG) turbulence model. Results indicated that, for a pooled stepped chute with θ=8.9°, increasing pool heights increased flow resistance, and for a chute with a steeper slope, θ=26.6°, flow resistance remained quasi-constant. Four configurations for openings were further tested: centered, offset, inline, and staggered configurations. Results demonstrated that the staggered configuration reduces residual head at the end of the chute. Additionally, the data revealed that, as the dimensions of the openings increases, flow resistance decreases. The findings of this research could be used as a general guideline for practical cases where openings should be embedded in pooled stepped chutes.