This paper presents the numerical simulations of flow and dam body sediment transport over a movable bed due to an earthfill dam break. The RANS equations, together with the k-ω SST turbulent model, are employed. The phase characteristic parameter is used as the phases of air, water, sediment, and bulk of dam body. The system of equations is solved numerically using the PISO algorithm. The numerical model is first verified using the dam break experimental data from the literature. The model successfully captures the temporal changes in the measured flow depths, pressures, wave fronts, and arrival times. The verified model is then applied to simulate the flow and sediment transport as a result of an artificial earthfill dam break having an obstacle at its downstream section. The simulations show that there is a noticeable decrease in the shock pressures at all points around the obstacle and there is an increase in the water levels. The bulk dam body sediment moves together with the water flow while spreading. It takes longer time for the sediment laden flow to reach the obstacle. The investigation of dam body formed by different soils shows that the soil type has minor effect while the transport of sediment can raise the water levels and change the morphology of the downstream section.