Goulart,E.S., Calliari, L.J.,2013. Medium-term morphodynamic behavior of a multiple sand bar beach. Cassino beach, located in southern Brazil, is a very fine sand beach with morphodynamic stages ranging from dissipative to intermediate. This beach can display up to three sand bars which are active during high energy events. Since the beach is located in a microtidal area, flood events are mainly caused by storm surges which can reach 1.8 m. During such events the highest rates of beach erosion are observed. A series of six years (from March 2005 to February 2011) of data from video images have been used to study the nearshore morphodynamic behavior. Daily data of sandbars and waterline position were obtained from these images. The generated data was analyzed in order to recognize flood events patterns as well as patterns of beach morphodynamic both during flood events and during normal conditions. Forty seven flood events were identified, 53% during winter, 24% during autumn, 17% during spring, and 6% in the summer. The average duration of events is 1.5 days. During this period, the whole system is migrating offshore in a rate of 9 m/year. Wavelet analysis showed a gradation of frequencies that govern the variability of the surf zone features. Closer to the beach high frequencies processes (associated with tides and meteorological forcing) have larger influence than further offshore, where longer processes gain importance.

Extratropical cyclones are the main drivers of high-energy wave events along the southern coast of Brazil, frequently producing hazardous coastal conditions. Between 2001 and 2020, we identified 51 high-impact coastal storms based on Marine Weather Warnings and ERA5 reanalysis. Events showed a clear seasonal pattern, with the highest occurrence in winter and autumn. Composite analyses revealed that these extreme events are consistently associated with strong meridional pressure gradients and southerly to southeasterly low-level winds, which establish long wind-fetch zones that favor the generation and shore-normal propagation of energetic waves. Significant wave heights typically exceeded 4 m along the entire coastline, with maxima south of 35° S. EOF analyses showed that the dominant mode of variability is a recurrent low-pressure system centered between 40 and 45° S over the southwestern Atlantic. In contrast, the second mode represents the dipole between continental high pressure and oceanic low pressure that intensifies storm-related wave generation. Case studies from 2008 and 2015 confirmed that these synoptic patterns result in prolonged hazardous sea states and coastal impacts, including bar closures at the Port of Rio Grande, totaling 355 h of inoperability. These findings provide a clear characterization of the meteoceanographic patterns associated with high-impact coastal storms in southern Brazil and offer a climatological basis for improving early warning, navigation safety, and coastal risk management.

Este artigo mostra os impactos da elevação do nível do mar (ENM) e do balanço sedimentar (BS) no recuo da linha de costa (LC) para 2041 e 2100, no setor do Farol da Conceição, Rio Grande do Sul, Brasil. Para entender estes comportamentos na região foi usado um modelo de larga escala, Randon Shoreface Translation Model (RanSTM), capaz de simular o efeito ENM, do BS e da geomorfologia na variação da LC. Foram realizadas quatro simulações distintas, visando: i) estimar o BS de 1996-2018, utilizando a taxa de ENM regional; ii) projetar as futuras LC para 2041 e 2100, baseados nas estimativas da ENM para o século XXI; iii) quantificar a influência isolada da ENM e do BS nas taxas de recuo da LC; iv) analisar a influência da geomorfologia da antepraia adjacente no recuo. Os resultados encontrados para as simulações mostram um déficit de sedimento de -1000 m³/m para o período de 1996-2018, e a taxa de recuo da LC foi de -2,95 m/ano. As projeções mostram que as taxas médias de erosão vão aumentar para 2041 e 2100 (-3,85 e -4,23 m/ano, respectivamente). Nas últimas décadas e para 2041 o recuo da LC foi dominado pelo BS negativo; no entanto para 2100 a principal componente do recuo é a ENM. Quando analisado a influência da geomorfologia, o setor com a menor declividade apresentou as maiores taxas de recuo da LC.