Hydraulic erosion in dam spillways poses a significant threat to dam infrastructure, requiring the evaluation of hydraulic and rock mechanic parameters. In this study, the hydraulic parameters of a smooth surface unlined spillway were evaluated using Computational Fluid Dynamics modeling (CFD) based on a 1:40 reduced-scale model of the Hydro-Quebec Romaine 4 spillway. While physical experiments can yield reliable results, they are costly and subject to scale effects and several errors, including on kinetic estimates. Numerical simulations, on the other hand, offer a cost-effective and accurate approach. Accordingly, the Flow3D software, which employs the Finite Volume Method, was used to properly anticipate flow behavior and 3D fluid motion patterns using the renormalization group turbulence model with the volume of fluid approach. Measurements along the channel demonstrate a reasonable tendency whereby velocity increases from upstream to downstream of the spillway. In addition, we observed a smooth and quasi-linear decreasing water height in the open channel. The study offers an understanding that can help future hydraulic structure design by determining the critical flow parameters along the spillway.