Caracterização geológica, geomorfológica e evolutiva holocênica do litoral sul de Jaguaruna, SC, Brasil

Understanding the evolutionary processes that occurred for the current conformation of the coastal environment is very important for studies related to the planning and coastal management. This study aims to characterize the Holocene coastal barrier at the southern sector of Jaguaruna, Santa Catarina, in terms of geology, geomorphology and evolution, by analyzing surface and subsurface data, to support the coastal management in the region. The study was based on aerial photographs interpretation and geophysical analysis of GPR data. Four sedimentary deposits were identified on the surface of the coastal barrier: Eolic Deposit, Beach-Marine Deposit, Beach-Lagoonal Deposit and Paludal Deposit. Geomorphologicaly, these deposits occur as sand dunes, strandplain and wetlands, respectively. Furthermore, precipitation ridges and paleochannels are also found in the morphology of the barrier. Regarding the subsurface information, the main observation is the influence of the Urussanga River in the shallow marine and beach environment during the barrier evolution. The presence of paleochannels in subsurface along with other surface information allowed the characterization of the evolutionary behavior of the barrier as regressive. The GPR sections enable to identify the paleochannels due to the presence of concave erosive surface with high amplitude and lateral continuity. Above these surface occurs paleochannels filling in different phases. These geological and geomorphological information have important implications for the planning and territorial management.Compreender os processos evolutivos que ocorreram para a conformação atual do ambiente costeiro é de suma importância para estudos relacionados ao planejamento e gestão do litoral. O presente trabalho tem como objetivo caracterizar a barreira costeira holocênica do setor sul de Jaguaruna, Santa Catarina, do ponto de vista geológico, geomorfológico e evolutivo, através de dados de superfície e de subsuperfície, a fim de subsidiar a gestão costeira da região. O estudo foi realizado com base na interpretação de fotografias aéreas e na análise de dados geofísicos obtidos com um GPR. Em superfície foram identificados quatro depósitos sedimentares compondo a barreira costeira: Depósito Lagunar Praial, Depósito Paludial, Depósito Eólico e Depósito Marinho Praial. Do ponto de vista geomorfológico, esses depósitos se apresentam na forma de planície de cordões litorâneos, banhados, dunas e praia, respectivamente. Além destes, cristas de precipitação e paleocanais se destacam na morfologia da barreira. Quanto às informações de subsuperfície, a principal observação está relacionada à influência do Rio Urussanga sobre o ambiente marinho raso e praial durante a evolução da barreira. A presença de paleocanais em subsuperfície, juntamente com outras informações identificadas em superfície, permitiram caracterizar o comportamento evolutivo da barreira como regressiva. As seções de GPR possibilitaram identificar os paleocanais devido à presença de uma superfície erosiva em forma côncava, com alta amplitude e continuidade lateral. Acima dessa superfície ocorre o preenchimento dos paleocanais em fases distintas. Estas informa- ções de caráter geológico e geomorfológico têm implicações importantes para o planejamento e gestão territorial

Control factors in the evolution of Holocene coastal barriers in Southern Brazil

The evolution and behavior of coastal barriers are controlled by several allogenic and autogenic factors. Some of these may be more deterministic than others. In this study, the GEOMBEST morphostratigraphic model is used to evaluate the degree of influence of both the substrate slope and the long-term sedimentary budget on the evolution of an extensive lagoon-barrier system during the mid-late Holocene in the middle littoral of Rio Grande do Sul state (Southern Brazil). Along this coastal stretch there is a coexistence of barriers with regressive, transgressive and stationery morphological behavior over >200 km. The modern configuration of the Holocene system (shoreline position and the lagoon-barrier width) was reproduced through the variability of two factors: the substrate slope (which defines the horizontal and vertical distance that the barrier will translate and rotate) and the sedimentary budget (which controls the evolution of the barrier when sea level oscillates slowly). The substrate slope of the middle littoral, between 0.021° and 0.149°, determined the cross-shore position of the shoreline, and the exogenous input or removal of sediment (estimated between −8 to +4.5 m3/m/a) allowed establishing the type of barrier behavior in the last millennia. Thus, the substrate slope exerts both direct and indirect control on coastal evolution. According to sensitivity analysis, a small decrease in the slope of the substrate, on the order of 0.001°, can increase the resulting barrier translation by >150 m, considering a 1-m rise in sea level over a 100year interval

Geomorphological responses due to storm wave events at Praia da Barra, Garopaba – Santa Catarina State, Southern Brazil

This work presents a beach morphodynamics analysis for Praia da Barra, located in the municipality of Garopaba, Santa Catarina State, Brazil. Praia da Barra has sectors with a natural beach/dune system and sectors where the foredune is completely anthropized. In 2017, during autumn and winter, eight storm wave events reached the study area, resulting in a coastline retreat and infrastructure damages at the site and along the southern Brazilian coastal zone. This work applied two methodologies to study the impacts of storm waves at the study area, 1) Four photogrammetric surveys using UAV high-resolution Orthophoto and DEMs for monitoring geomorphological changes at the site, before and after storm wave events in 2017; and 2) wave simulation using the SMC-Brazil platform to assess wave and current patterns from three main wave directions scenarios. The authors integrated the results from both methodologies to understand the behavior of Praia da Barra’s beach/dune system when attacked by storm wave events. The authors identified erosive hot spots at Praia da Barra that are concentrated at the central sector of the beach, which presents more anthropization. While the northern and southern sectors present a vegetated and well-developed foredune system, they also presented a higher resilience against the storm events that hit Praia da Barra during the autumn and winter seasons of 2017

Geomorphological responses due to storm wave events at praia da barra, garopaba – Santa Catarina state, southern Brazil

his work presents a beach morphodynamics analysis for Praia da Barra, located in the municipality of Garopaba, Santa Catarina State, Brazil. Praia da Barra has sectors with a natural beach/dune system and sectors where the foredune is completely anthropized. In 2017, during autumn and winter, eight storm wave events reached the study area, resulting in a coastline retreat and infrastructure damages at the site and along the southern Brazilian coastal zone. This work applied two methodologies to study the impacts of storm waves at the study area, 1) Four photogrammetric surveys using UAV high-resolution Orthophoto and DEMs for monitoring geomorphological changes at the site, before and after storm wave events in 2017; and 2) wave simulation using the SMC-Brazil platform to assess wave and current patterns from three main wave directions scenarios. The authors integrated the results from both methodologies to understand the behavior of Praia da Barra's beach/dune system when attacked by storm wave events. The authors identified erosive hot spots at Praia da Barra that are concentrated at the central sector of the beach, which presents more anthropization. While the northern and southern sectors present a vegetated and well-developed foredune system, they also presented a higher resilience against the storm events that hit Praia da Barra during the autumn and winter seasons of 2017

Strategies for the management of the marine shoreline in the orla araranguá project (Santa Catarina, Brazil)

The Orla Project is a tool of the Brazilian Coastal Management resultant of joint action between the Environment Ministry and the Planning Ministry. This project articulates the three spheres of the government (federal, state, and municipal) and society. Its actions seek the management of the coastal spaces, approaching the environmental and heritage politics. The construction of a Plan for the Integrated Management of the Coastline occurs through workshops with the development of methodologies of diagnosis construction, classification and formulation of scenarios. The classification of the coastline integrates the strategic planning, which will subsidize the decision making process to reach the desired scenarios. Araranguá municipality started its workshops in October 2014, with lectures and discussions between technicians from the federal and state governments, and coordination by the municipal government. During the project period, a field day and more than 40 workshops were developed, which had the participation of the community and public managers. As a result of the workshops, the coastline was sectored by its landscape, typology (exposed, semi-exposed, and sheltered), and levels of occupation in five sectors (S1 to S5). The project identified 40 problems in the area, some recurrent in all sectors and a few specific of some places. In order to solve these problems, 80 actions and measures with different priorities were defined. From the workshops of the Orla Project, it was possible to identify the need to create rules for the use of Araranguá coastline, thus enabling its conservation and helping its sustainable development

Análise espaço-temporal dos ventos no extremo norte da Planície Costeira do Rio Grande do Sul, Brasil

The sediment transport between different regions is strongly influenced by wind activity, which can have great influence on the formation of coastal landscapes. Aiming to characterize the wind dynamic in the extreme north of Rio Grande do Sul (RS) Coastal Plain, historic and annual wind data (speed and direction) of four meteorological stations located in the region were analyzed in this study. Results show that in Torres station the winds that occur more often are from NE and S, and winds from W and N are rare. In the SBTR/Airport station, winds from the N-NE quadrant are the most frequent (32%), followed by the winds from SW, SSW and S. In the Central Itapeva Lake station the wind pattern changes slightly, and the most frequent wind directions are NE and SW, with more intense winds coming from SW. It was verified also a variability in the winds directions and frequency during different seasons, with more intense winds during winter. Based on the wind data from each meteorological station, it was found that in the extreme north of RS Coastal Plain the greatest winds intensity (S-SW quadrant) occur at the station which is located further south (Arroio do Sal Municipality), which is closer to the Serra Geral scarps, where the wind direction coincides with the direction free of orographic obstacles. Nevertheless, the spatial-temporal analysis showed that the different localities do not have significant differences in wind directional patterns considering the directional unit as the quadrant.O transporte de partículas entre diferentes regiões é fortemente influenciado pela atividade dos ventos, o qual pode exercer grande influência na formação das paisagens litorâneas. Com o objetivo de caracterizar a dinâmica dos ventos no extremo norte da Planície Costeira do Rio Grande do Sul (RS), foram analisados dados históricos e anuais dos ventos (velocidade e direção) de quatro estações meteorológicas localizadas na região. Os resultados demonstram que na estação de Torres os ventos provenientes das direções NE e S são mais frequentes, e que os ventos das direções W e N são raros. Na estação SBTR/Aeroporto, os ventos do quadrante N-E são os mais frequentes (32%), seguidos dos ventos provenientes das direções SW, SSW e S. Na estação da Lagoa Itapeva Central o padrão dos ventos se altera um pouco, prevalecendo as direções NE e SW, com ventos de maior intensidade provenientes da direção SW. Verificou-se uma variabilidade considerável na direção e frequência dos ventos no decorrer das estações do ano, apresentando maiores valores de intensidade durante o inverno. Com base nos dados obtidos para cada estação meteorológica, constatou- -se que no extremo norte da Planície Costeira do RS os ventos de maiores intensidade (quadrante S-SW) são registrados na estação localizada mais ao sul (município de Arroio do Sal), mais próxima à base do Planalto Serra Geral, numa localidade em que as ocorrências coincidem com as direções livres de obstáculos orográficos. Apesar disso, as análises espaço-temporais evidenciaram que as diferentes localidades não possuem diferenças significativas nos padrões direcionais do vento considerando a unidade direcional como sendo o quadrante

Moluscos holocênicos em sedimentos lagunares associados à barreira arenosa da Pinheira-Guarda-Gamboa, Santa Catarina: implicações paleoambientais

This paper documents the occurrence of mollusk carbonate fossils in sediments of the backbarrier of the Pinheira-Guarda- -Gamboa beaches, Santa Catarina Coastal Plain, southern Brazil, in which five species of gastropods and nine of bivalves were recognized. Among the bivalves, four species were articulated, Ostrea equestris, Anomalocardia brasiliana, Lucina pectinata and Tagelus plebeius, and the last three were found in life position. Radiocarbon datings were performed on articulate and life position specimens: Lucina pectinata, indicating a conventional age of 5.260 ± 30 years BP. (calibrate age 5.620 - 5.440), Tagelus plebeius, 5.620 ± 30 years BP. (calibrate age 6.000 - 5.840) and Ostrea equestris articulate, 5.410 ± 30 years BP. (calibrate age 5.805 - 5.580), indicating the material in the middle Holocene. The topographic data gathered with precision equipment established that the top of the outcrop is 2 m above the relative sea-level. The fossil association suggests lagoon-estuarine environment subsequently filled in response to a lowering of the sea level.Este trabalho documenta a ocorrência de moluscos fósseis carbonáticos em sedimentos da retrobarreira das praias da Pinheira-Guarda-Gamboa, Planície Costeira de Santa Catarina, sul do Brasil, onde foram reconhecidas cinco espécies de gastrópodes e nove de bivalves. Dentre os bivalves, identificaram-se quatro espécies articuladas, Ostrea equestris, Anomalocardia brasiliana, Lucina pectinata e Tagelus plebeius, as três últimas registradas em posição de vida. Datações radiocarbônicas foram realizadas em espécimes articulados e em posição de vida: Lucina pectinata apontando idades convencionais de 5.260 ± 30 anos AP (idade calibrada 5.620 - 5.440), Tagelus plebeius, 5.620 ± 30 anos AP (idade calibrada 6.000 - 5.840) e Ostrea equestris apenas articulado, 5.410 ± 30 anos AP (idade calibrada 5.805 - 5.580), posicionando o material no Holoceno médio. O dado topográfico com equipamento de precisão estabeleceu que o topo do afloramento encontra- -se a 2 m acima do nível relativo atual do mar. A associação indica um ambiente lagunar-estuarino, posteriormente colmatado como resposta ao rebaixamento do nível do mar

Arquitetura deposicional da barreira holocênica na porção meridional da Ilha de São Francisco do Sul, SC, Brasil

The geophysical method GPR (Ground Penetrating Radar) together with subsurface sampling with a vibrocore allowed to characterize the sedimentary facies and depositional architecture of the Holocenic portion of the Ilha de São Francisco do Sul coastal plain, located in the northern region of Santa Catarina State. The study area was divided into two distinct blocks, north and south, according to the sedimentary architecture defined by radar stratigraphy. The collected data allowed the characterization of beach, eolic, lagoon and estuarine depositional environments in the radargram profiles. The north block has reflectors consistent with barrier progradation during the sea level fall of 2.5 m in the last 5,000 years. At south block the reflectors show clear influence of paleochannels systems and spits in the barrier development, where the progradation occurred under the influence of the Babitonga paleoestuary dynamics.O método geofísico do radar de penetração no solo (GPR) juntamente com sondagens utilizando um vibrotestemunhador permitiram caracterizar as fácies sedimentares e a arquitetura deposicional da porção holocênica da planície costeira da Ilha de São Francisco do Sul, litoral norte de Santa Catarina. A área de estudo foi dividida em dois blocos, norte e sul, segundo a arquitetura deposicional definida através da estratigrafia de radar. Os dados obtidos permitiram a caracteriza- ção dos ambientes de sedimentação praial, eólico, lagunar e estuarino nos radargramas. No bloco norte são interpretados refletores condizentes com a progradação da barreira, relacionada com a queda de nível do mar de 2,5 m nos últimos 5.000 anos. No bloco sul, os refletores mostram clara influência de sistemas de paleocanais e esporões arenosos no desenvolvimento da barreira, onde a progradação se desenvolveu sob a influência da dinâmica do paleoestuário da Babitonga