THREE DIMENSIONAL MODELING OF SEDIMENT TRANSPORT UPSTREAM OF AL-BETERA REGULATOR-IRAQ

Abstract

This paper represents an analytical study, simulation (flow field and sediment movements) and estimation of the sediment deposition for the Al- Betera river reach upstream of Al-Betera regulator – Maysan Governorate–Iraq. Field measurements techniques and SSIIM Model were used for these purposes. A river reach with length of 4250m was chosen and divided to 17 cross sections. The Model solves the Navier – stokes equations for calculating the water velocity with k-ε model for predication the turbulence (shear stress). The Model is a stepping stone in the field of Computational Fluid Dynamics (CFD). Sediment rating curve was established by using the historical data (1984-2014) of the suspended sediment loads and river discharge which considers as a reference for researchers who interest in the field of sediment transport. Plan form of river morphology was classified as a straight (1.07 sinuosity) for the period 1986, 2007and 2014. In this study, a new sediment load transport rate equation by using multiple linear regression analysis was developed. The results of evaluation showed that the new model performs better than many Researchers [Ackers(1973) , Yang(1996), Van Rijn(1987) , Ariffin (2004) and Jassim (2012) ]. A graphical representation of 3D velocities was obtained by simulation and by using Power law Scheme (x-y,y-z,x-z planes). Good agreements were found between the simulated and measured values of the flow velocity and sediment concentration in 3D for the selected 3 nodes in the y direction and for 3 depths of flow. The Coefficient of determinations were (0.8- 94) and (0.72- 0.98) respectively. The annual trapped sediment load for a river discharge (80.2) m3/sec was (13816) cubic meters of deposition material of sediment which represents approximately (4.1 cm/year) along the river reach. SSIIM Model is a powerful fluid dynamic model for evaluation and estimation of water flow sediment transport and bed deposition. It has given satisfactory results for the bend in the river reach of the study. However, the grid, roughness of the bed and the sediment parameters must be chosen with suitable values taken for convergence purposes and taken into account the change of hydraulic and sediment variables with time and space.