Investigation of Polrood Dam Break due to Overtopping and its Resulted Flood Routing in the Downstream

Storage dams are constructed for several aims such as; water supply, flood control and energy generation. Dams are being threat by breakage and cause severe financial and human losses in downstream. If dam breakage phenomenon and its resulted effects are furcated before dam construction, the losses will be reduced in the future. In this study, the Polrood dam breakage due to overtopping has been investigated by BREACH GUI model. Results showed that the flood hydrograph due to dam breakage possessed a discharge peak of 47253 m3/s. This peak occurs 27 hrs after flood beginning an hour after overtopping.Then, flood routing was carried out in order to determine the effects of dam breakage by HEC-RAS model. The results of flood routing showed that the discharge peak arrived at the last cross section of 15 km distances in the dam downstream after 54 minute which possessed a decrease of 62%. The overlay of floodplain maps with Google Earth model showed that 18 villages and some regions of Kelachay and Rahim-Abad cities are affected by flooding in dam downstream. The flood resulted of this dam breakage, also causes river erosion near to the dam.