Browsing by Author "Pais-Barbosa, Joaquim"
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- Analysis of Nonlinear Wave Parameters on Ofir Sandy Beach (NW Portugal)Publication . Abreu, Tiago; Silva, Paulo A.; Baptista, Paulo; Pais-Barbosa, Joaquim; Fernández-Fernández, Sandra; Ferreira, Caroline; Matos, JoãoThe characterization of wave transformation processes in the nearshore is of paramount importance when it comes to assessing storm and flooding impacts, sediment transportation and deposition, harbors safety or design of coastal protective structures. This study analyzes nonlinear wave parameters on Ofir sandy beach. This beach is located along the northwest Portuguese coast which is a highly energetic coast exposed to waves generated far away in the Atlantic Ocean. Despite the existence of rocky outcrops in the nearshore and intertidal zones at the study site, reducing the wave energy that reaches the beach, the study site exhibits pronounced erosive processes. Field observations of six near-bottom pressure records collected at the intertidal zone help to characterize the evolution of wave nonlinearities which are directly associated with sediment transport mechanisms. Data results show that there is an interrelation between the characteristics of the waves and the local morphology. It is also possible to ascertain, more clearly, the level of asymmetry present in the waves propagated at different depths, contributing to a better understanding of the local morpho-hydrodynamics.
- Longshore Transport Estimation on Ofir Beach in Northwest Portugal: Sand-Tracer ExperimentPublication . Fernández-Fernández, Sandra; Baptista, Paulo; Martins, Virgínia A.; Silva, Paulo A.; Abreu, Tiago; Pais-Barbosa, Joaquim; Bernardes, Cristina; Miranda, Paulo; Rocha, Mariana V. L.; Santos, Fábio; Bernabeu, Ana; Rey, DanielThis work aims to shed some light on longshore sediment transport (LST) in the highly energetic northwest coast of Portugal. Data achieved through a sand-tracer experiment are compared with data obtained from the original and the new re-evaluated longshore sediment transport formulas (USACE Waterways Experiment Station’s Coastal Engineering and Research Center, Kamphuis, and Bayram bulk formulas) to assess their performance. The field experiment with dyed sand was held at Ofir Beach during one tidal cycle under medium wave-energy conditions. Local hydrodynamic conditions and beach topography were recorded. The tracer was driven southward in response to the local swell and wind- and wave-induced currents (Hsb=0.75mHsb=0.75m, Tp=11.5sTp=11.5s, θb=8−12°θb=8−12°). The LST was estimated by using a linear sediment transport flux approach. The obtained value (2.3×10−3m3⋅s−12.3×10−3m3⋅s−1) approached the estimation provided by the original Bayram formula (2.5×10−3m3⋅s−12.5×10−3m3⋅s−1). The other formulas overestimated the transport, but the estimations resulting from the new re-evaluated formulas also yield approximate results. Therefore, the results of this work indicated that the Bayram formula may give satisfactory results for predicting the longshore sediment transport on Ofir Beach.