Tidal simulation revisited

Accurate representation of tides is a pre-requisite for simulating many complex coastal processes. This study examines several most important factors for rigorous validation of nearshore tides: bottom friction, quality of DEM (Digital Elevation Model) information, horizontal resolution of model mesh, and 3D baroclinic effects. The results demonstrate that a rigorous model validation against tide gauge observation requires (1) good-quality DEM information be available; (2) locally very high mesh resolution (which has not been used in previous models) be used to capture the small-scale bathymetric/geometric features near the tide gauges; and (3) 3D effects be included. On the other hand, attempts to compensate errors by tuning other parameters such as bottom friction might produce erroneous results away from the validation sites, as tides undergo complex nonlinear transformations in the nearshore regime. Consequently, a most skilled tidal simulation should use a 3D model with locally very high resolution to faithfully represent DEMs of good quality (not just high resolution). Our results also highlight the central role played by the bathymetry on coastal processes.