Modelagem numérica da dinâmica da maré no estuário dos Bons Sinais

Abstract

The tidal dynamics in the estuaries or simply estuarine hydrodynamics are basically governed by three factors, the discharge of the river, the tidal currents and the wind tension, subject to changes by Earth’s rotation by bathymetry and estuarine geometry. In this way, the aim of the present research is to understand the variations in tidal dynamics in the Bons Sinais estuary with emphasis on the variations/modifications of tidal wave due to its interaction with the bathymetry and estuarine geometry while the tide propagates up estuary. For this purpose, the hydrodynamics of the Bons Sinais estuary was simulated for a period of 30 days using the three-dimensional hydrodynamic circulation model ELCOM (Estuary Lake and Coastal Ocean Model), set up with both in situ and remote data. Then, the process of validation of the ELCOM model results was performed, in which the tide and tidal current produced by the model were compared to field measurements. In order to analyze the dynamics of the tidal wave resulting from the interaction with the bathymetry and estuarine geometry the t_tide package (Pawlowicz et al., 2002) was used to remove the non-tidal component which comes from other factors. Results from the validation of the ELCOM model indicated a good approximation to reality, with calculated RMSE (Root Mean Square Error) of 0.03 and 0.2, and 𝑅2 (Squared Correlation Coefficient) of 0.99 and 0.77, for height and tidal current, respectively. According to the results related to morphological factors, the convergence of the margins and the friction of the bottom, there are zones along the estuary classified as hyposynchronous (attenuation of the tidal wave) and other ones classified as hypersynchronous (amplification of the tidal wave). For tidal asymmetry, the results showed dominance of the M2 and M4 combination, followed by S2 and S4 combination, characterized, in general, by ebb dominance. Finally, the dissipation of tidal energy along the estuary is associated with currents, which show, in general, straight relation with the width of the cross section, thus suggesting less influence of bottom friction in tidal energy dissipation.