Sediment Transport Simulation under Flood Propagation by 2D HEC-RAS for Tigris River, Iraq

Changes in the hydrological regime significantly affect water quality and sediment delivery in all river systems. Sediment transport analysis aids in better understanding fluvial dynamics. This paper focuses on river dynamics, which maintain the environment and support low-cost training activities and flood control constructions. The work aims to evaluate the total load sediment transport rate in the case of unsteady non-equilibrium under the condition of flood in 2D waves adopted within the 2D HEC-RAS model. The Tigris River, between the Mosul Dam and Samarra Barrage, was selected as the case study. In addition, advection and diffusion formulas are applied to simulate the rate of sediment transport based on the length of the adaptation parameter. Manning's roughness coefficient corresponding to the land cover has been calibrated. The outputs represented the obtained maps that were incorporated with the Digital Elevation Model (DEM) with a 100 m grid size, which describes the regions exposed to erosion and deposition in 2D. The average length of adaptation was 80.1 m. Furthermore, high variation in the sediment transport rate due to flood waves near Mosul Dam, where the sediment transport rate is 8100 kg m-1 s-1 at 5 km, which corresponds to a flood flow of 205000 m3/s, then decreases to 1600 kg m-1 s-1at km 422. The Laursen-Copeland model provides more precise results in simulating sediment transport, riverbed elevation changes, and sedimentation patterns. Finally, the study enhanced the control plan by providing details about a critical risk in inundation areas.