Comparative two-dimensional and three-dimensional numerical analysis of steady flow through a levee breach

Lateral outflow through a levee breach generates complex three-dimensional (3D) flow structures that are challenging to simulate using two-dimensional (2D) depth-averaged models. Although widely used, a comprehensive study quantifying the limitations of the 2D approach is lacking in existing literature. Moreover, 3D models have also not been systematically examined to simulate steady flow through fully developed levee breaches. This study presents a comprehensive comparative assessment of two-dimensional and three-dimensional modelling approaches for simulating levee-breach flows. The model results are validated against existing experimental data pertaining to rectangular and trapezoidal channel breaches. The study highlights the limitations of the 2D depth-averaged model in capturing the free surface level and the longitudinal and transverse velocity characteristics at the breach locations. The 3D model, however, accurately reproduces the flow and turbulent characteristics near the breach and provides deeper insights into the three-dimensional flow characteristics induced by the lateral outflow.