Improved 2D Shallow Water Model Able to Capture the Effects of Complex Bathymetric Features through Their Subgrid Modeling

In this study, an improved two-dimensional (2D) model is proposed for simulating shallow water flows over complex bathymetry through their subgrid modeling. The proposed model delineates the detailed unevenness in the topography of selected 2D elements that are usually ignored in other common 2D hydrodynamic models by specifying the bed elevation at more than one point in an element. The relationship between submerged area and water stage and the relationship between water volume and water stage can then be preprocessed for every specified element. The process is similar to how cross sections are handled in standard one-dimensional models. Thus, the 2D model can simulate the open channel flow accurately and efficiently, with only one element been applied over the channel width. The proposed model was tested using a hypothetical channel flow with an analytical solution and a real river-coast system with measured data. The simulations showed that the model could achieve the same level of accuracy using a coarse mesh as that obtained by previous 2D models with a refined mesh. The proposed 2D model performs well at predicting shallow flows over complex terrain, which is usually handled by coupled models.