A coupled one- and two-dimensional hydrodynamic model was developed to simulate the flood wave propagation through the breaches. The Preissmann scheme was used for the one-dimensional model and the Roe scheme on unstructured meshes was used for the two-dimensional model. The special boundaries, such as roads and irrigation ditches, were generalized as broad crested weirs and were linearized. A coupled model with real terrain was established through coupling the unstructured mesh and special boundaries, and the dry and wet depth theory was used to optimize this model. The model was applied to simulation of a levee-breach flood that occurred in the West Irrigation Area of the Qingtongxia Gorge of the Yellow River. The results show that the model can truly simulate the flood wave propagation and flood inundation area in the calculation area, and can simulate the water-blocking effect of roads and irrigation ditches and water-passing effect of bridges and culverts.