J. M. V. Samani - Department of Irrigation Hydraulic Structures, College of Agriculture, Tarbiat Modares University, Tehran, Islamic Republic of Iran.
M. Heydari - Department of Irrigation Hydraulic Structures, College of Agriculture, Tarbiat Modares University, Tehran, Islamic Republic of Iran.

Rock has been advantageously employed in hydraulic structures such as rockfill dams, gabion weirs and drain works. One rockfill dam applications can be flood control in wa-tershed management. The objectives of building rockfill detention dams are flow storage for a specific period and lowering of the outflow hydrograph. As this type of dam consists of coarse particles, seepage flow will deviate from Darcy’s law and mostly be turbulent. Under the practical conditions of watershed management, it might be necessary to build successive rockfill dams, where a final outflow hydrograph with lower peak flows and longer duration is needed. Due to their reciprocal effects, the hydraulics of successive rockfill detention dams are complicated. This paper describes a routing flow model through successive rockfill dams considering the storage among them and their effects on each other. In the developed model, the velocity has been introduced to the ۱-D continuity equation as an exponential relationship between Reynolds number (Re) and the Darcy-Weisbach friction factor (f). By introducing the inflow hydrograph and rockfill character-istics as input data to the model, the outflow hydrograph can be determined through the storage routing method. The results of the developed model show good agreement with the experimental data collected for this investigation. The results show that the degree of peak reduction of the routed hydrograph depends on the number of successive rockfill dams, the distance between them, the average size of the rockfill material, and the dam dimensions.

Non-Darcy flow, Reservoir routing, Rockfill dams