Estimation of Bottom Friction in Modeling Tidal Dynamics of Port Phillip Bay

Abstract Knowledge of bottom friction plays a crucial role in the modeling of coastal ocean hydrodynamics. Existing formulations based on the grain size to estimate the friction coefficients are often imprecise, impacting the performance of numerical models. This study adjusted the estimated friction coefficient based on the specific habitat characteristics of the seabed in Port Phillip Bay. The effectiveness of this method is substantiated through modeling surface elevations within the bay and comparing the results with observational data. Through sensitivity experiments, it was found that the scaling factors should be chosen depending on the seabed characteristics and could vary by one to two orders of magnitude. The impact of the adjusted bottom-friction coefficient on the simulated tides in the bay is also analyzed. Revised estimates of bottom friction significantly improve our capability to predict surface elevations with implications for modeling waves, tides, and sediment transport in Port Phillip Bay.