Effects of Watershed Management Practices on Some of Flood Characteristics Change in Haftan Watershed

Evaluation of watershed projects is one of the most fundamental problems in countries for future implementation planning and management of natural resources. In regard to lack of required equipment for monitoring and evaluation of watershed projects and investigation of management measures in watersheds, application of hydrologic models is an efficient tool for simulation of watershed behavior before and after implementation of watershed projects. So, this study was carried out in order to evaluate of hydraulic structures using HEC-HMS in the Haftan watershed, Markazi province, Iran. For this purpose, with use of rainfall-runoff data from two storm events the initial rainfall losses and curve number parameters were calibrated. Then, the model was validated using one event. Finally, six hours rainfall was used as design storm for flood simulation before and after construction of check dams along the water ways. Variation of runoff lag time due to changes in channel slope because of construction of check dams was evaluated. Finally, after definition of peak discharge error percentage as objective function, effect of construction of protective hydraulic structures on flood hydrograph properties were evaluated. Results showed that watershed management constraction operations have the most effect on small flood events. Waterways could decrease both flood peak and flood volume.. So with increasing in rainfall intensity, the effect of structure have been decreased. Also the results of this study showed that implementation of protective hydraulic structures cause 21 to 83 percent decrease in flood peak and 11 to 79 percent decrease in flood volume. It can be concluded that protective hydraulic structures are more effective on decrease in flood peak compare to decrease in flood volume.