Abstract: A special lattice Boltzmann rmdel for simulating 2-D unsteady open channel flows is built by combining the Chapman-Enskog-Expansion derived multi-scale equations that approximate the form of shallow water equations.To verify the model typical 1-D and 2-D dam breaks are simulated,and the results show agreement with analytical method and other models.As an actual example,the unsteady flows in the tailrace channel of a hydropower plant are calculated.