Brazil has about 8500 km of coastline that is mostly undeveloped. However, the pressure of fast-growing coastal urban centers is already impacting the shore. This paper characterizes shore protection works in Hermenegildo Beach, evaluates their efficiency to protect property against the impact of storm events, and presents the response of beachfront owners to erosion. Hermenegildo is a beach village located 12km north of the border with Uruguay in Rio Grande do Sul, the southernmost state in Brazil. Several factors contribute to beach erosion in Hermenegildo: storm surge, redistribution of wave energy, rising sea level, the presence of an underlying layer of impermeable peat, and human activities. The shoreline is heavily armored with about 61% of beachfront houses protected by revetments (30%), seawalls (18%), or a combination of both (13%). A strong storm struck the Rio Grande do Sul coast in 16 April 1999 and resulted in severe beach erosion and destroyed 22 houses, besides all concrete structures, half of the quarrystone revetments, and 80% of the timber seawalls. Shore protection structures in Hermenegildo are threatened by erosion because: (1) they were built too close to the water, (2) shoreline retreat has been observed, and (3) armoring has reduced beach width. Most of the beachfront owners are aware of the severe beach erosion problem and appear to understand basic coastal dynamics. About 82% of the interviewed beachfront owners lost property due to erosion; 88% subsequently built protection structures to prevent further loss. Surprisingly, 88% of those who did not experience property damage also built defense structures. Armoring is commonly an initiative of beachfront owners who build low-budget structures without consultation by technical experts.

Waves generated by South Atlantic storms are greatly responsible for the beach and coastal erosion verified at the central coast of Rio Grande do Sul State, Brazil. These beaches are classified as intermediate, according to the morphodynamic approach suggested by the “Australian School of Coastal Geomorphology”. The storm wave regime controls the morphodynamic variability of those sandy beaches. Through the classification proposed by Dolan and Davis (1992). South Atlantic storms were classified and related to meteorological systems, considering corresponding beach responses. Out of the 3 year wave gauge storm data analyzed, 54.4% corresponded to Class I (weak), 23% to class II (moderate), 19.25% to class III (significant), 2.75% to class IV (severe) and for class V (extreme), 1 storm was recorded (0.6%). Coincidently, the proportion of storm class frequencies for the 3 year data of South Atlantic storms showed to be similar to the 42 year data studied by Dolan and Davis (1992) for North Atlantic storms. Such classification has proved to be effective for the southern Brazilian coast. Autumn and winter are the storm periods with greatest intensity, wich associated to maximum spring tides and storm surges generate the erosion cicle at this coast. The inverse process is verified to spring and summer, when the accretion cicle takes place. In addiction to this seasonal behavior trend, a continuous process of erosion without further recovering occurred at Conceição Lighthouse and Lagamarzinho beach locations, at rates of 3,6 meter per year and 1 meter per year respectively. The use of such method made possible quantifying storm intensity and establishing its relationship to seasonal erosion processes taking place in the southern Brazilian beaches.

Resumo Este trabalho visa analisar a variabilidade morfológica de perfis de praia obtidos na praia do Pântano do Sul, sul da ilha de Santa Catarina. Três perfis de praia foram analisados, mensalmente, entre agosto de 2002 e agosto de 2003. Um perfil extra foi realizado para elucidar a presença de megacúspides. Características de onda na zona de surf foram medidas através da observação visual a cada perfil. Durante o período de amostragem dos perfis de praia, o regime de ondas em águas profundas também foi monitorado, através de dados coletados por um ondógrafo direcional localizado a cerca de 35 km da ilha de Santa Catarina. As variações morfológicas dos perfis ocorreram em decorrência de quatro principais fatores: (i) Do grau de exposição dos diferentes trechos da praia às ondas incidentes. Quando mais exposta à ação de ondas, a praia tendeu a apresentar maiores variações no estoque sedimentar; (ii) Da ação de ondas de alta energia na praia, caracterizada pela incidência de ondulações de sul-sudeste com período de pico de onda acima de 10 s e altura significativa acima de 4 m, em águas profundas, condição que gera erosão da porção subaérea da praia; (iii) Da ação de ondas de baixa energia na praia, que geralmente acarreta deposição sedimentar da praia subaérea; (iv) Da própria morfologia rítmica da praia, que pode gerar variações locais na declividade e no volume entre perfis medidos sobre pontas ou embaiamentos das megacúspides.

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