Abstract: Accurate prediction of maximum scour depth at groin heads has always been the key concern for the design of spur dikes. The simulation of flow and sediment transport processes around spur dikes in tidal rivers often involves the application of three-dimensional hydrodynamic models. In this study, a three-dimensional (3D) turbulence model is developed to simulate the sediment transport around spur dikes in tidal rivers. Using the 3D model, the local scour processes around spur dikes are simulated under both tidal current flow and unidirectional steady flow conditions. The result shows that both local scour processes and resulting scour patterns under the two conditions are significantly different from each other. It is thus important to correctly identify the flow conditions for the design and construction of spur dikes.