Flow Modulation on Hydraulic River Behavior between Al-Abbassia and Al-Shammia Barrages Using HEC-RAS2D

The construction of hydraulic structures worldwide results in controlled hydrologic regimes through river impoundment. The studied area exhibits a fluctuation in climatic change and flow regulation by hydraulic structures, resulting in variations in flow patterns. This study investigates the variations in the water flow of the Euphrates River in the vicinity of Abbassia Barrage. Three flow scenarios, maximum flow 44.26 m3/s, average flow 28.69 m3/s, and minimum flow 19.67 m3/s for one year, were processed in HECRAS2D software and analyzed to view the impact of flow modulation on hydraulic river behavior between Al-Abbassia and Al-Shammia Barrages. The findings indicate that the hydraulic behavior of the entire river is influenced by changes in the river's hydraulic characteristics due to flow modulation, such as flow velocity, water surface elevation (WSE), and water depth. The flow velocity values ranged from 2.16 m/s, 1.83 m/s, and 1.55 m/s, while the water surface elevations were 19.2–29.4 m, 19.05–29.02 m, and 18.7–28.8 m for maximum, average, and minimum flow conditions, respectively. In terms of water depth, the values ranged from 2.85–7.94 m in straight river sections, and from 3.51–6.86 m in meandering sections, depending on the flow conditions. These results offer valuable insights into the future behavior of river channels under various flow scenarios, which can help in addressing issues arising from prevailing fluvial processes.