Morphodynamical analysis of Goes Beach (Guarujá) based on topographic profiles, coastal transport models and shoreline planform approach

Abstract

Góes Beach is an embayed beach between rocky headlands located at the southern of the Santo Amaro Island, in Guarujá County (Baixada Santista Metropolitan Region), in front of and closer to the Santos Port navigation channel. This channel is being currently dredged in order to deepen it from 14 m down to 15 m and to widen it from 150 m to 220 m. This work, as well as the future increase in vessel traffic could change the Góes Beach morphodynamics. Since last year, this beach is under a natural process named beach rotation (inversions in lateral movement of sand along the beach in response to a modification in the incident waves direction), which has been responsible by heavily sand deposition on its eastern ending, where coastal erosion used to dominate before it. Although the clear benefits for the beach, the silting of the pier located on this area has been making difficult the approach of boats into the shore, then causing several problems for the local community. Studies carried out since January 2010 blame the phenomenon to reversals in the longshore currents caused by a shift in the incident waves direction due to successive storm surges since February until December. The purpose of this research is to investigate the Góes Beach morphodynamics under the beach rotation in progress, especially after the dredging works that should be ended by November 2011. In addition, the study aims to point the most suitable areas for the construction of a new pier. The beach will be monthly monitored through six beach profiles, during one hydrological year. Wave climate measurements, including natural waves and those induced by ships and boats, will be carried out weekly. Results will be applied into computer models embracing sediment transportation (transverse and longitudinal) and shoreline planform approaches (Model of Equilibrium Planform of embayed beaches). In addition, stratigraphic surveys, including dating of samples, will be done in order to identify past records of beach rotation.