The effect of the islands on the nature of the flow of the Tigris River Using HEC-RAS

Abstract

Erosion and sediment deposition are key factors that affect the hydraulic behavior of rivers and the stability of hydraulic structures. This study investigates these processes downstream of the Al-Kut Barrage, where mid-Channel Islands influence the natural flow pattern of the Tigris River. A one-dimensional hydrodynamic model was developed using HEC-RAS to simulate flow conditions and assess the impact of island removal on erosion–deposition under different discharge scenarios. The model was calibrated and validated using field data from the study reach, showing a strong agreement between observed and simulated results (r = 0.998) with a Manning’s roughness coefficient of 0.03. The results show that the existing islands have a minor effect on flow capacity and flood wave attenuation. After modifying the cross-sections and removing the islands virtually, the discharge decreased by 3.59 m³/s (around 0.34%), indicating a slight improvement in wave dissipation and delay. Although the effect was limited, the study highlights the need for continuous monitoring and maintenance of the Tigris River channel to preserve its hydraulic performance and reduce sedimentation impacts downstream of the Kut Barrage.