Numerical Investigation of River Meander Morphodynamics: An Enhanced 2D Modelling

Abstract

The interplay of sediment transport, flow hydraulics, and bank erosion processes controls the intricate morphodynamic behavior of meandering rivers. The primary cause of meander bend formation and evolution is curvature-induced secondary circulation, which promotes inner-bank deposition and increases outer-bank erosion, resulting in progressive channel migration and alternating bar-pool sequences. Many current models are based on simplified curvature-based formulations that do not adequately represent turbulence structure, sediment redistribution, and dynamic width adjustment, despite considerable progress from theoretical analyses, laboratory experiments, and numerical simulations. Additionally, vertical flow structures are suppressed by the majority of two-dimensional depth-averaged methods, while fully three-dimensional models are computationally demanding and infrequently integrated with full morphodynamic coupling. To increase the physical realism of meander evolution simulations, this work creates an improved two-dimensional morphodynamic model. The framework combines the depth-averaged shallow-water equations with a physics-based bank migration algorithm that permits variable channel width, a hybrid eddy-viscosity turbulence formulation, a curvature-driven secondary flow representation, and flexible sediment transport models for both bedload and suspended load. The Exner sediment continuity equation is used to calculate bed evolution, and an adaptive curvilinear grid is used to preserve geometric consistency and numerical stability during channel deformation. A structured curvilinear mesh with explicit time-stepping and finite-difference discretization is used to solve the model while adhering to morphodynamic and hydrodynamic stability constraints. Realistic development of alternating bars and pools, curvature-controlled redistribution of shear stress, outer-bank intensification of erosion, and progressive morphodynamic adjustment toward quasi-equilibrium conditions are all demonstrated by simulations performed on a laboratoryscale sine-generated channel. Strong agreement between the results and well-known benchmark studies attests to the validity of the suggested framework. In addition to offering practical relevance for river engineering, flood hazard mitigation, and sustainable channel restoration, the developed modeling approach offers a strong basis for future extension to fully three-dimensional simulations.