The Roughness Effects on the Dam-Break Flood Waves Propagation in a Sloping Hydraulic Model

The possibility of dam failures due to seismic forces, bombardment, piping, overtopping, or mal-designing and construction considerations is probable and can result in the most notable human life losses and extensive property damages. The knowledge of the propagation of the flood waves resulted by dam failure and the resistance effects of bed roughness on the flow velocity variation in the downstream of the dams have an important role in the hydraulics of free surface flows. In the present paper the rapidly varied unsteady flow caused by the failure of a model dam in a rectangular sloping rough channel with dry down stream bed has been analyzed theoretically using the characteristic method on the dimensionless form by means of computer and compared with experimental data existing in the literature. It is concluded that the positive wave front and drying wave front are highly sensitive to hydraulic resistance, consequently increasing the bed roughness causes to decreasing the flow velocity. Also by approaching the positive wave front, the flow velocity increases and tends to the value of wave front velocity. Finally, comparison revealed that experimental data of rough sloping channel agreed closely with the theoretical one. Thus this latest method would provide more satisfactory results for sloping rough channels.