Estimation of bottom friction in modelling tidal dynamics of Port Phillip Bay

Abstract Knowledge of bottom friction plays a crucial role in the modelling of coastal ocean hydrodynamics. Existing formulations based on grain size to estimate 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 modelling 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 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 modelling waves, tides and sediment transport in Port Phillip Bay.