Hydrodynamic Model-Based Evaluation of Sediment Transport Capacity for the Makhool-Samarra Reach of Tigris River

Abstract

This paper implemented an HEC-RAS-based steady two-dimensional hydrodynamic model to evaluate the hydraulic characteristics and Sediment Transport Capacity (STC) of the Makhool-Samarra Reach of the Tigris River, where this part is not already investigated. This model was prepared with the aid of topographical surveys, hydraulic measurements, and laboratory tests, as well as recorded data. The main findings show that the flow velocities within most of the studied reach are considered high compared to the local and worldwide flow velocity ranges in natural rivers. Also, the Toffaleti sediment transport function with the Van Rijn fall velocity and the effective depth-to-width computation methods are the most compatible and suitable methods for computing the Sediment Transport Potential (STP) in the ‎studied reach. With the maximum flow, the computed STP was less than the average (5.7×106 tons/day) in 45% of the reach length, where the maximum STP is 8.7×106 tons/day. However, with the minimum flow, the STP intermittently fluctuates below the average (0.2×106 tons/day) in 48% of the reach length, where the minimum STP is 0.14×106 tons/day. Generally, these STPs are little more than the Tigris River in Mosul and much higher than that in Baghdad. Also, these STPs are considered high on a global scale, especially during high flow. Medium gravel is the larger grain gradation class that can be transported. It constitutes less than 0.00005 % of the STP. Furthermore, the STC computations clearly show that the suspended sediment is the dominant part of the STC and the bed material constitutes less than 0.002% of the STC of the total load. However, most of the STC ‎concerns the clay and very fine silt.