Anabranching, sedimentation, island growth, and bank scouring are key morphological processes occurring in the Tigris River. These processes can disrupt navigation, affect water intake, and compromise the safety of infrastructure near the riverbanks. This study aims to simulate and assess the responses of a 4.75 km meandering–anabranching reach of the Tigris River in Baghdad city center to various alternative groyne dimensions designed to control natural morphological processes, using a depth-averaged hydro-morphodynamic model (Delft3D-FM). Bathymetric and field measurements, including sediment load, velocity, water level, and discharge, were conducted and used for model calibration and validation. The model demonstrated good agreement with observed water levels (Root Mean Square Error (RMSE) = 0.02 m) and depth-averaged velocities (RMSE = 0.068–0.142 m/s), and it reproduced morphological changes with a maximum bed-level error of approximately 13% at control sections. More than 20 groyne configurations, varying in orientation, length (L), and spacing (S), were simulated and assessed. In this study, the selection of the best groyne design for controlling morphological processes in the target reach was carried out using a proposed composite Groyne Performance Index (GPI). The index is based on weighted contributions from flow partitioning, thalweg stability, cross-channel infilling, island-margin response, and corridor deposition. While the straight–groyne configuration with L = 0.25 W (river width) and S = 2 L achieved the highest GPI, the L = 0.25 W and S = 3 L configuration is selected as the preferred design as it provided a more balanced response in terms of flow redirection, thalweg stability, reduced anabranching and deposition, and lower scour risk. The adopted selection methodology demonstrates a valuable indicator-based framework for selecting river-training layouts in low-slope, sand-bed, meandering–anabranching reaches of alluvial rivers.
Rasheed et al. (Tue,) studied this question.