We conducted a numerical study under existing experimental conditions, and evaluated the advantage of the inclusion of two-way coupling on the bed-formations. The flow is solved by RANS model and sediment is modeled with DEM. A two-way coupling between particles and flow is applied by incorporating a particle-fluid interaction terms of drag force, with and without shielding effect. The numerical results were compared with an existing experimental result and the accuracy of the simulations is discussed. We found that the feedback effect from the sediment phase to the flow phase has an important role to determine the characteristics of the bedforms.