Effect of Tail Regulators on Euphrates River Flood Capacity at Al Nassiriyah City

Euphrates River extends about 125 km within the study area located in Annassiriyah City, Dhi Qar Governorate, Iraq. The impact of the seven hydraulic structures on the discharge capacity of the Euphrates River needs to be considered. The main objectives of this research are to increase the discharge capacity of Euphrates River within Annassiriyah City during flood seasons and study the impact of these hydraulic structures on the river capacity by using HEC-RAS 5.0.3 software. Five scenarios were simulated to study the different current condition of Euphrates River within Annassiriyah City. Other additional four scenarios were implemented through river training to increase the river capacity to 1300 m³/s; it is the flood of 100 year return period. The results of the current condition showed that the maximum discharge capacity of Euphrates River within Annassiriyah City is just 300 m³/s. The results of applied improvements show that the capacity can reach 1300 m³/s when Al Chibayish Weir was hypothetically removed from the river system. Additionally, the river capacity will be reduced to 600 m³/s when Al Chibayish Weir is considered. It was concluded that the 100-year flood discharge cannot be achieved without removing Al Chibayish Weir from the river system.