Characterizing the mean flow and time-dependent features of very shallow flows under macroroughness conditions is of great importance in many practical applications in the science of fluid mechanics. For example, understanding the flow over stepped spillways, the particular macroroughness flow addressed in this study is important from practical and theoretical points of view. In first place, there is a significant number of dams under construction that include a stepped spillway as an overtopping flow structure. Second, understanding the time-averaged and the instantaneous flow features immediately upstream of the aerated region of stepped spillways will lead to a better understanding of the complex process of air entrainment. The objective of this study is to address that portion of the flow from a numerical point of view. Numerous numerical computations of the skimming flow were compared against existing experimental data on a 1V:0.8H slope stepped chute. The physical description provided in this research can be used to further investigate the process of air entrainment.