In this paper, the effect of the sediment bed elevation on dam-break flow over mobile beds is scrutinized using the volume of fluid (VOF) method. While the equations of motion are tackled employing the finite-volume, standard k-ε closure model and the van Rijn bed load formula. The results show that an increase in the downstream bed elevation leads to reducing: a) the flow advancing distance and water rising over the end wall, b) the sediment transport rate downstream and c) the reservoir releasing rate. Further, the decrease in level-difference results in in-creasing the sheet-flow height. However, it does not affect the critical specific downstream of the dam. It causes the formation and evolution of two hydraulic jumps and scour holes in the near field and the downstream channel. The dimen-sions of the first scour hole are larger than the second one.

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