Modeling Storm Surge with Subgrid Corrections Accounting for Unresolved Topography

In numerical modeling of storm surges, bottom topographical features that are smaller than the model grid resolution, such as small channels, could in fact represent important flow passages conveying water from one area to another. The predictive capability of the model could suffer greatly from the absence of such subgrid details, especially in inundation and recession zones of flow in previous-dry and wet areas. We investigate the use of subgrid corrections accounting for unresolved topography in shallow coastal water flow and storm-surge modelling. The investigation is conducted within the context of finite-volume-based and finite-element-based shallow water flow solvers. Numerical results demonstrate that the subgrid corrections can greatly improve the model performance of the coarse-grid solutions with relatively small additional computational expense.