AbstractFor safe design of culverts, the estimation of scour depth downstream of the culvert outlet is one of the most remarkable considerations. Poor design of culverts inevitably leads to destruction and increases expenditures on management and rehabilitation. The objective of this study is to investigate the performance of numerical models in predicting scour depth and its location downstream of box culverts in unsteady flow conditions. Culverts with unblocked and partially blocked outlets were used, and the predictions of two turbulence methods, namely renormalization group (RNG) and k-ε, were compared. Comprehensive experimental data of box culverts from the literature were used and the numerical models were performed in commercially available software. The downstream profile of scour development, maximum scour depth, and its location were obtained and compared with observed data. It was found that the numerical model was in good agreement with the experimental data. In both turbulence models, the scour depth increased with increase of discharge in the raising limb of the hydrograph, whereas for lower discharges in the falling limb of the hydrograph, the scour depth decreased.