Simulação numérica da incidência de ondas marítimas em praias de Natal/RN, Nordeste do Brasil, 2012 a 2014

Abstract

Along the coast of the Rio Grande do Norte, are verified peaks of erosion in sandy beaches with negative impacts from the social and economic point of view, in that maritime waves were important source of energy for carried of sediments. In this study, was ascertained the incident wave regime on the part of the coast eastern of the Rio Grande do Norte, especially on the shoreline between Ponta Negra beach and Via Costeira, extension of the urban coast in Natal/RN, between the years of 2012/2014. A SWAN numerical simulation model was applied. This model was developed by the Delft University of Technology, operated by the graphic interface SOPRO, of the National Laboratory of Civil Engineering of Portugal. As initial boundary conditions in open sea, significant height information was used, average period and direction of wave propagation from the Wavewatch III (WWIII) base. The bathymetry was represented by the Nautical Charts 810 and 22100 of Brazilian Navy and the water level of tide gauge at Port of Natal. For segmentation in seasonal intervals, Cluster Analysis was applied to the WWIII series, testing the significance of the groups by ANOVA test of variance. The months from January to April and from June to September were organized into two groups, corresponding to predominant conditions of summer and winter, respectively. The months of May and October are part of another group that represents transitions among the first. November and December integrated a fourth group of wave regime during the studied period. It was observed the highest percentile of significant height exceeded 2.42 m, with maximum in 2.97 m mainly between the months of May to September. The year 2014 presented more energetic scenarios of wave incidence. Most of occurrences were around 1.59 m. The occurrence of longer waves (long period) are concentrated around 7.14 s, with percentile 99 starting the 10.58 s, maximum 13.35 s. The most recurrent direction of propagation was near 99 degrees azimuth (East Southeast) with higher declines than 134 degrees (Southeast), influenced by the variations of the trade winds of the flows generated by South Atlantic High Pressure System and by the Eastern undulatory disorders. In general, the city of Nísia Floresta received the highest waves during the period. In the extension of Ponta Negra and Via Costeira the cove of Morro do Careca has attenuated undulation by diffraction of the promontory, where the period varied around 7.55 s and height of 0.65 s and the incidence of energy increased toward Via Costeira, with period of 6.88 s and height of 0.76 m during the winter months.