Unsteadiness Parameter Effect on Sediment Transport under Flash Flood

Significant impact of flood flows on river morphology changes is obvious. The sudden floods are caused more damage. Sudden and heavy showers feature of arid and semiarid regions is an important factor that can produce such a flood. A numerical and experimental results model was combined in this research and the sediment transport evaluated in unsteady flow on moveable bed. First numerical model was calibrated by initial condition and boundary condition of experiments data. Then some of hydraulic parameters which changes in time were derived. Study of mechanism sediment transport under flash flood is the aim of this research that it’s modeled experimentally in flume with change in slope. Since the flood analysis was down as unsteady flow.  Some Hydrographs were generated with peak different discharge rates. The sediment was used has median size, 1.5, 2, 3 mm. Independent parameters effects on sediment transport are: maximum discharge of hydrograph, bed slops, time duration of hydrograph and hydrographs form (triangle – trapezoidal). The results show that equilibrium and stability of hydrographs are suitable. Also the unsteadiness dimensionless number has an important role on sediment transport and for this study the range of it’s , that will shows a minimum Froude number for particle motion is necessary. The hydrographs which have higher unsteadiness can to transport more of sediment