investigating the effect of dredging sistan river islands on the flood level reduction

Amount of helmand river flow as the most important source of surface water in sistan plain is controlled by factors from outside of political boundaries. therefore management of river flow and sediment is not possible at upstream of helmand river. there are a lot of destructive flood in the history of sistan plain so it is necessary to control of sistan river bed. in this regard, this study examines the impact of dredging sistan river islands on the flood level reduction. in this study sistan river simulated using hec-ras model. hec-ras model is able to calculate annual sediment and hydraulic variables in mobile bed condition. after calibration of model and choosing the best sediment transport function, flow in sistan river is simulated before and after dredging. results showed that after removal of the islands has just increased river discharge from 600 cms to 700 cms.