A three-dimensional numerical model for shallow flow based on a layer-integrated solution method is developed in this paper. The controlled equations are solved using an efficient operator-splitting finite element method on adaptive triangle grids. The experiment data in mending channel flow is selected to verify the proposed model. The simulated results are in satisfactory agreement with the experimental data. Therefore, the present 3D shallow flow model is a robust and efficient tool for simulating the shallow flow hydrodynamics.