Comparative Analysis of Overland Flow Models Using Finite Volume Schemes

In this paper the attention is firstly focused on a comparative analysis of three hydraulic models for overland flow simulations. In particular, the overland flow was considered as a 2D unsteady flow and was mathematically described using three approaches (fully dynamic, diffusive and kinematic waves). Numerical results highlighted that the differences among the simulations were not very important when the simulations referred to commonly used ideal tests found in the literature in which the topography is reduced to plane surface. Significant differences were observed in more complicated tests for which only the fully dynamic model was able to provide a good prediction of the observed discharges and water depths. Then the attention is only devoted to the fully dynamic model and in particular on both the analysis of two numerical schemes (TVD-MacCormack and HLL) and the influence of the grid size. Numerical tests carried out on irregular topography showed that, as the grid size decreased, the performances of the HLL scheme were more similar to those of the TVD-MacCormack scheme in shorter computational times at least for high rainfall intensity.