Polerood river morphological variations in the downstream of dam, pre and post dam construction in short term scale

With construction of storage dams، a large amount of sediments are accumulated behind them. Therefore، water released from the dam is so clear and possesses high sediment transport capacity، which causes the river erosion at downstream the dam. In this research، Polerood river morphological variations predicted in downstream of dam using mathematical models for a short period post dam construction. Then، results were compared with lack of dam existence manner. Results showed that، the presence of the dam causes more erosion in the river. Maximum erosion in presence and lack of the dam were 4. 7 and 3. 7 m، respectively. The maximum influence of the dam construction on river morphology is up to 10 km downstream from the dam axis. At far distances، river bed variations in both the presence and lack of the dam were the same and the intensity of these variations was very low. The most river variations occurred at early years and variations intensity reduced gradually. Results also showed that erosion and sedimentation in the river is balanced by the time and river will be arrived at a regime case.