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Nesta contribuição descrevemos como os dados referente ao número de casos positivos para COVID-19, reportados em cada um dos 21 agrupamentos estabelecidos pela secretaria de saúde pública do estado do Rio Grande do Sul (RS), entre os meses de Março de 2020 e Junho de 2021, são obtidos, georreferenciados e utilizados como suporte para a modelagem matemática proposta, a qual descreve de maneira preditiva a evolução da COVID-19 no estado. Tal conjunto de dados epidemiológicos, bem como as informações da progressão da COVID-19 provenientes da modelagem matemática são armazenadas em um banco de dados como parte do projeto “Exactum - Núcleo Transdisciplinar de Teoria, Modelagem, Tecnologia e Educação de Combate a Surtos, Endemias, Epidemias e Pandemias”

One of the great challenges faced due to current human demands is to reconcile the conservation of the innumerable natural resources present in the marine realm with the intense development processes occurring in the coastal zones. The latter aspect includes Marine Spatial Planning (MSP), an important management tool created to establish a more rational organization of the use of marine and coastal areas, equalizing the demands of development with the need to protect these ecosystems. Some of the most important international organizations — the European Union, OSPAR, HELCOM/VASAB, and the International Council for the Exploration of the Sea (ICES) — are encouraging MSP at a national level. Another efficient tool is Ecosystem-based Management (EBM), which allows a full arrangement of interactions within the marine realm and effectively integrates science and governance for the management of natural resources. This work aims to propose an integrated analysis methodology using an EBM approach that encompasses environmental variables and current and potential uses, contributing to the implementation of marine spatial planning for the inner continental shelf surrounding the Patos lagoon estuary. Datasets were used to produce the thematic maps, such as surface sedimentology, location of the ecologically important submerged features, occurrence of mineral resources and zoobenthic fauna, with trophic importance and/or endangered. A sedimentological map was initially drawn; it was possible to observe the predominance of fine sand sediments between the coastal zone and the 50 meter isobaths, together with some coarse and medium quartzose sand and shell gravel deposits. The identification of these sedimentological patterns is fundamental in the understanding of the benthic communities, in addition to creating subsidies for the conservation of species. The present study proposes the creation of zones for exclusive use and multiple-use based on the surveys and mapping of the environmental and socioeconomic features of the region.

This work aims to evaluate the application of geotechnologies in the construction of Digital Surface Models (DSM) for two washouts located at Cassino Beach, Rio Grande, RS. The use of geotechnologies such as remote pilot aircraft (RPA) and GNSS-RTK receiver resulted in the construction of six DSMs, two for each flight day, of channels with Ground Sample Distance (GSD) between 5.05 cm and 5.26 cm. We emphasize that the use of RPA and application geoprocessing techniques are of great value in the improvement of studies on the coastal areas and washouts of the Cassino beach. Este trabalho teve como objetivo avaliar a aplicação das geotecnologias na construção de Modelos Digitais de Superfície (MDS) para dois sangradouros localizados na praia do Cassino, município do Rio Grande, RS. O emprego das geotecnologias, como a aeronave remotamente pilotada (ARP) e o receptor GNSS-RTK, resultou na construção de seis MDS, dois para cada dia de voo, dos canais com resolução espacial entre 5,05 cm e 5,26 cm. Ressaltamos que o uso das técnicas de geoprocessamento e a aplicação da ARP são de grande valor no aprimoramento de estudos sobre as zonas costeiras e os sangradouros do Balneário Cassino.

Recentemente uma alternativa para o levantamento de fotografias áreas vem crescendo no mundo e no Brasil. Trata-se da utilização de “drones”. Apesar de diversos trabalhos com drone estarem sendo realizados atualmente, ainda há a necessidade do compartilhamento de ideias e experiências com enfoque metodológico, por tratarem-se de uma tecnologia há pouco popularizada. O presente trabalho visa apresentar informações com foco metodológico, derivadas de mais de dois anos do uso de um drone, modelo DJI Phantom 3 Professional, em segmentos da costa central e sul do Estado do Rio Grande do Sul. Serão apresentados neste trabalho, o equipamento utilizado, detalhes da configuração da câmera, os modos de voo (manual e automatizado), um fluxograma de trabalho, um checklist de campo e considerações sobre o processamento e a análise de mosaicos de fotografias aéreas de drone, de modelos digitais de superfície e do terreno, perfis de praia e cálculo de variação de linha de costa que podem ser realizados a partir de dados coletados com este equipamento. Pretende-se, com isto, contribuir para a realização de trabalhos futuros com este tipo de equipamento, ou similares, na análise de ambientes costeiros, sobretudo em praias e dunas, podendo ser aplicado em outros trabalhos de análise ambiental. A B S T R A C T Recently it has growing all over the world, including Brazil, an alternative for aerial photogrammetric surveys. With the utilization of drones. Although many studies having been made using drones, nowadays we still have the necessity of sharing ideas and experiences through a methodological approach, because drones thecnology having been only available recently. This paper aims to show informations through a methodological approach, derived from more than two years of use of a drone, model DJI Phantom 3 Professional, in the segments of central and southern coast of the state of Rio Grande do Sul. It will be showed on this paper, the equipment used, details of camera configuration, flight models (manual and automatized), a flow chart of work, field checklist and considerations about the processament and analysis of drone aerial photographic mosaics, digital surface models and digital terrain models, beach profiles and shoreline change calculation that can be made through this equipament. It is intended to contribute for the realization of future work, with this kind of equipment, or similar one, on coastal environmental analysis, specially on beaches and dunes, being able to be applied in other environmental analysis studies.

This paper presents the validation of the End Point Rate (EPR) tool for QGIS (EPR4Q), a tool built-in QGIS graphical modeler for calculating the shoreline change with the end point rate method. The EPR4Q tries to fill the gaps in user-friendly and free open-source tools for shoreline analysis in a geographic information system environment since the most used software—Digital Shoreline Analysis System (DSAS)—although being a free extension, it is created for commercial software. Additionally, the best free, open-source option to calculate EPR is called Analyzing Moving Boundaries Using R (AMBUR), since it is a robust and powerful tool, the complexity can restrict the accessibility and simple usage. The validation methodology consists of applying the EPR4Q, DSAS, and AMBUR with different types of shorelines found in nature, extracted from the US Geological Survey Open-File. The obtained results of each tool were compared with Pearson’s correlation coefficient. The validation results indicate that the EPR4Q tool acquired high correlation values with DSAS and AMBUR, reaching a coefficient of 0.98 to 1.00 on linear, extensive, and non-extensive shorelines, proving that the EPR4Q tool is ready to be freely used by the academic, scientific, engineering, and coastal managers communities worldwide.

The Cassino Beach is a low-lying coast with high inundation susceptibility in southern Brazil. To map this vulnerability, a low cost alternative to the increasingly employed fine-scale remote sensing is the employment of a digital camera coupled with unmanned aerial vehicle (UAV). However, this was only achieved through the adoption of photogrammetric principles and computational advances of structure-from-motion (SfM) algorithms. The study objectives were: a topographic reconstruction of the Cassino beach; an accurate digital terrain model (DTM) generation from the dense cloud classification; and inundation maps based on representative concentration pathway (RCP) scenarios from the Intergovernmental Panel on Climate Change using the bathtub approach. The primary input of the inundation model was a DTM with spatial resolution of 0.1294 m and an RMSE elevation of 0.0607 m. The high-resolution and vertical precision were appropriated to the bathtub approach, with the mapping identifying the exposed areas with the drowning potential correctly connected to the source. The inundation maps revealed that: in the 2046–2065 RCP scenario, the urban drowned area has varied between 37 and 41%; in the 2081–2100 RCP scenario, the urban drowned area has varied between 51 and 73%; and in the 2100 RCP scenario, the urban drowned area has varied between 54 and 82%. The bathtub modeling shows that low-lying coasts are highly susceptible to sea-level rise effects, and the use of UAV-SfM technology in the production of topographic data was suitable for the study area.

Recentemente uma alternativa para o levantamento de fotografias areas vem crescendo no mundo e no Brasil. Trata-se da utilizacao de “drones”. Apesar de diversos trabalhos com drone estarem sendo realizados atualmente, ainda ha a necessidade do compartilhamento de ideias e experiencias com enfoque metodologico, por tratarem-se de uma tecnologia ha pouco popularizada. O presente trabalho visa apresentar informacoes com foco metodologico, derivadas de mais de dois anos do uso de um drone, modelo DJI Phantom 3 Professional , em segmentos da costa central e sul do Estado do Rio Grande do Sul. Serao apresentados neste trabalho, o equipamento utilizado, detalhes da configuracao da câmera, os modos de voo (manual e automatizado), um fluxograma de trabalho, um checklist de campo e consideracoes sobre o processamento e a analise de mosaicos de fotografias aereas de drone, de modelos digitais de superficie e do terreno, perfis de praia e calculo de variacao de linha de costa que podem ser realizados a partir de dados coletados com este equipamento. Pretende-se, com isto, contribuir para a realizacao de trabalhos futuros com este tipo de equipamento, ou similares, na analise de ambientes costeiros, sobretudo em praias e dunas, podendo ser aplicado em outros trabalhos de analise ambiental. A B S T R A C T Recently it has growing all over the world, including Brazil, an alternative for aerial photogrammetric surveys. With the utilization of drones. Although many studies having been made using drones, nowadays we still have the necessity of sharing ideas and experiences through a methodological approach, because drones thecnology having been only available recently. This paper aims to show informations through a methodological approach, derived from more than two years of use of a drone, model DJI Phantom 3 Professional, in the segments of central and southern coast of the state of Rio Grande do Sul. It will be showed on this paper, the equipment used, details of camera configuration, flight models (manual and automatized), a flow chart of work, field checklist and considerations about the processament and analysis of drone aerial photographic mosaics, digital surface models and digital terrain models, beach profiles and shoreline change calculation that can be made through this equipament. It is intended to contribute for the realization of future work, with this kind of equipment, or similar one, on coastal environmental analysis, specially on beaches and dunes, being able to be applied in other environmental analysis studies.

Leal Alves, D.C.; Espinoza, J.M.A.; Albuquerque, M.G.; Silva, M.B.; Fontoura, J.S.; Serpa, C., and Weschenfelder, J., 2018. Bathymetry estimation by orbital data of OLI sensor: a case study of the Rio Grande harbor, southern Brazil. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 51–55. Coconut Creek (Florida), ISSN 0749-0208.In the coastal and estuarine systems, the determination of bathymetric data is an important instrument for a safe shipping in harbor zones. Generally, data are collected in situ or ground, however, this information is time-consuming and costly. Remote sensing can be regarded as one of the most promising alternative tools to map bathymetry of the estuaries and coastal zones, due to its extensive coverage of the area and the low cost imbued. This study aims to analyze the accuracy of bathymetric data obtained by the Operational Land Imager (OLI) sensor, coupled to Landsat 8 orbital platform, in comparison to the results with bathymetric data collected in situ (echo sounder) at the Rio Grande channel, situated in Patos Lagoon estuary, southern Brazil. With the bathymetric maps and data collected in situ, it was possible to estimate the estuary depth from Landsat 8 image; using the Coastal band (b1), with a spatial resolution of 30 m and penetration capacity of 15 m, and Near Infrared band (b5), with a spatial resolution of 30 m. The relation between the data collected in situ and the data obtained by remote sensing showed the accuracy of 71% kappa (index of accuracy) and R2 of 81.7% for the image referring to February 2015, nine months before the echo sounding survey. Nevertheless, the image processing for December 2015, one month after the survey with echo sounder, presented a kappa of 85%, and R2 of 96.5%. The results show a good correlation between the data acquired in situ and the data obtained by the OLI sensor. In this way, the remote sensing technique used for bathymetric analysis can be applied as a complementary form, increasing the temporal resolution of the obtained data.

Meteo-oceanographic events are characterized by low pressure centers and intense winds. These systems are responsible for transferring a huge amount of energy from the atmosphere to the ocean that could cause serious socioeconomics damages to the coastal zones. Some of the consequences of these events propagation are an occurrence of large amplitude waves and an increase in the coastal water level. This study aims to characterize the effects of the extratropical cyclone in the southern Brazil occurred in October 2016, seeking a relationship between this event and the recent erosive episodes. Using satellite images and data obtained by unmanned aerial vehicle (UAV), it was possible to trace the shoreline behavior at time intervals, where occurred actions of extratropical cyclones during the year of 2016. The comparison of the shoreline position data, obtained by the image of July 2016, and the UAV (obtained in September and November 2016) presented an approximated shoreline retraction balance of 5.91 m associated for the cyclone that occurred between October 26th and 27th, 2016. This event was associated with synoptic pattern, which have feature cyclogenesis in the Southern Uruguayan coast with a displacement to the east and trajectory between 28° and 43°S, with winds of 17.9 m s-1 and SW direction. Associated with the meteorological aspects, erosive process is frequently accelerated or augmented by anthropogenic action, which is mainly related to building constructions activities and sometimes contributes to the destruction of dunes. After the passage of cyclone there was a partial or total destruction of 40% of beachfront houses and 65% of coastal protection structures. Therefore, this type of study constitutes a basic tool of general interest in the coastal management, contributing to understanding of the impacts and risks associated with the coastal dynamics and effects of the meteo-oceanographic events, along the Soutrhern Brazil.

Wind energy is considered one of the most promising clean technologies for power generation. For the sustainable development of this industry, it is essential that planning integrate spatial zoning with estimates of installed capacity and energy production. A Geographic Information System-based methodology was developed to propose planning for wind farms from a spatial perspective in the extreme south of Brazil. Through multi-criteria evaluation, the feasibility of the study area for this activity was analyzed according to suitability and constraint criteria. The assessment of suitability was based on wind energy exploitation, while the constraint analysis was based on the environmental legislation, social aspects and exclusion areas. In the suitability analysis, importance weights were assigned to the variables according to the unprecedented combination of the Delphi, linear and geometric Analytic Hierarchy Process methods. Constraint and suitability maps were established for the wind farms. The integration of both aspects allowed the generation of a spatial zoning map. Based on this zoning, installed capacity was calculated according to technical characteristics of a reference wind turbine. Finally, energy production of the suitable zones was estimated. The proposed spatial planning aims to contribute to the licensing processes in southern Brazil. Furthermore, the methodology developed can be replicated in other similar case studies.

A linha de costa e uma feicao geomorfologica em que as mudancas topograficas podem acontecer ao longo de horas ou dias devido a ocorrencias de eventos de alta energia. Essa feicao e de importância estrategica para o planejamento ambiental das cidades costeiras, sendo necessario o seu monitoramento continuo. Este estudo propoe analisar a variacao da linha de costa na praia do Icarai, litoral de Caucaia – CE, a partir da aplicacao dos metodos Digital Shoreline Analysis System (DSAS) e Poligono de Mudanca. O recorte temporal de analise esta compreendido entre os anos de 2004 e 2018, pois o agravamento da erosao se deu particularmente nos anos 2000. Os resultados demonstram que os deslocamentos medios da linha de costa, tanto para o DSAS (-3,72 m) quanto para o Poligono de Mudanca (-3,41 m), se mostraram muito proximos. No entanto, quando observados parâmetros estatisticos mediana, desvio padrao e deslocamento minimo e maximo foi observada uma superestimacao das taxas obtidas pelo DSAS. A partir de uma analise de regressao linear foi observado que o Poligono de Mudanca (R² = 0,9471) se mostrou mais adequado, pois considera todo o segmento costeiro nos calculos de deslocamento. Tendo em vista os adjetivos e limitacoes dos metodos empregados, o Poligono de Mudanca apresentou um melhor desempenho tanto em termos estatisticos quanto aos erros inerentes. Por fim, estudos de abordagem comparativa entre metodos sao de grande importância para os gestores, visto que muitos municipios costeiros do Ceara e do Brasil tem apresentado problemas serios ligados a erosao costeira. Study of the shoreline behavior at Icarai beach (Caucaia, Ceara), using digital shoreline analysis system and the change polygon methods A B S T R A C T The shoreline is a geomorphological feature with variable topographic and subject to changes vary very quickly in the time-space scale, and may present major changes in a few hours, as in the occurence of storm surges. This feature is of strategic importance for the coastal cities environmental planning, being necessary its continuous monitoring. This study aims to analyze the shoreline variation at Icarai beach, Caucaia – CE coast, using two different methods: the Digital Shoreline Analysis System (DSAS) and the Change Polygon method. The analysis time frame is comprised between the years 2004 and 2018, since erosion worsened occurred particularly in the 2000s. The results showed that the average displacements from the shoreline, both for the DSAS (-3.72 m) and to Change Polygon (-3.41 m), were very close. However, when the other statistical parameters were observed (median, standard deviation, minimum and maximum displacement), an overestimation rates obtained by DSAS was observed. A linear regression analysis showed out that the Change Polygon method (R² = 0.9471), proved to be more suitable for the Icarai beach, as it considers the entire coastal segment in the calculation of shoreline displacement. Although both methods approaches have their adjectives and limitations, the Change Polygon showed a better performance, both statistical terms and in relation to inherent errors. Finally, studies that take into account the comparative approach between methos are of great importance for managers, given that many coastal municipalities in Ceara and Brazil have presented serious problems related to coastal erosion. Keywords: erosion, DSAS, change polygon, remote sensing.

Gonzaga, B.A.; Alves, D.C.L.; Albuquerque, M.G.; Espinoza, J.M.A.; Almeida, L.P.M., and Weschenfelder, J., 2020. Development of a low-cost ultrasonic sensor for groundwater monitoring in coastal environments: Validation using field and laboratory observations. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1001–1005. Coconut Creek (Florida), ISSN 0749-0208.This study presents the development and validation of a low-cost ultrasonic sensor (HCSR 04), coupled to an open source Arduino microcontroller platform, for groundwater monitoring in coastal environments. Given the fact that low-lying coastal zones are regions naturally prone to flooding (due to oceanic forcing and pluviosity) and densely occupied, monitoring groundwater variations is crucial for the management of flood-related events. A groundwater monitoring well was built, (made of a PVC pipe with 100 mm in diameter and 2 m long) and installed on the ground of a dune field, located in Cassino beach, southern of Brazil. The system was deployed for 84 consecutive days and programmed to perform water level measurements every 10 min. In laboratory, three units with the same hardware setup of the unit installed in the field (ultrasonic sensor coupled to the Arduino microcontroller) were installed on a 20 liter graduated PVC tube. Varying water levels were tested in the laboratory along the time (changing 1 cm every 2 minutes during 4 hours) in order to reproduce the synthetic signal. Eighty measurements were obtained for each sensor, a total of 240 for each validation process. For the laboratory validation, the results for nonparametric statistical tests (Kruskal and Wallis, and Dunn) presented a correlation of 99%, with Root mean square error (RMSE) 0.4113 and bias 0.0418. For the field tests, 3262 data collected by an ultrasonic sensor during 240 hours showed a means registration of 0.543 m. The minimum and maximum cataloged is 0.40 and 0.70 m, respectively, with 0.1076 m of standard deviation. Groundwater classical measurements, using a measuring tape, showed a mean and standard deviation of 0.544 and 0.1069 m, respectively. These preliminary tests showed that the developed monitoring system performs observations with an accuracy and precision within standard methods, therefore can be applied to monitoring changes in the level of groundwater.

As praias oceânicas arenosas são extremamente vulneráveis tanto aos fatores morfodinâmicos naturais quanto às ações antrópicas. O presente trabalho tem como objetivo quantificar e caracterizar, a partir de uma série temporal de imagens orbitais no intervalo de 2003 - 2015, a variação especial do limite entre a praia e a duna frontal nos Balneários Mostardense, Mar Grosso, Cassino e Barra do Chuí – RS, a fim de estimar se estão em processo de erosão, acresção ou estabilidade. A metodologia foi empregada a partir de uma base cartográfica adquirida no software GoogleEarthPro® e técnicas realizadas nos softwares ArcGis 10.3.1® e ERDAS Imagine 2013®. A variação da linha de costa foi obtida a partir do método polígono de mudança (Change Polygon Method), por meio de uma linha de controle aplicada ao limite praia duna frontal. Para o Balneário Mostardense, entre os anos de 2005 e 2014, se obteve taxa erosiva ao longo da costa. O Balneário Mar Grosso, entre os anos de 2006 e 2015, apresentou variações ao longo dos anos, predominando acresção e desenvolvimento dunar. O Balneário Cassino, entre os anos de 2006 e 2015, apresentou taxas acrescivas bastante significativas, associadas ao grande aporte sedimentar para a praia no período. O Balneário da Barra do Chuí, entre os anos de 2003 e 2013, apresentou taxas erosivas e acrescivas. Porém, segundo evidências no campo, constata-se que esse local está sofrendo processo erosivo. As variações do limite superior de praia, limite praia duna, têm relação com a ação de eventos de alta energia hidrodinâmica, que por vezes erodem as dunas frontais, e processos de recomposição, promovidos pela ação marinha e eólica. Os resultados mostraram também a importância das características locais no contexto da variação da linha de costa. Oceanic sandy beaches are extremely vulnerable both to natural morphodynamic factors and to anthropic activity. Based on a time series of orbital images collected from 2003 to 2015, this study aims at quantifying and characterizing the beach dune limit variation on Mostardense, Mar Grosso, Cassino and Barra do Chuí beaches, located in Rio Grande do Sul state, in the south of Brazil, in order to estimate if they are undergoing erosion, accretion or stability processes. The methodology is based on a cartographic base found at GoogleEarthPro® software and on techniques carried out by ArcGis 10.3.1® and ERDAS Imagine 2013®. Coastline variation was analysed by the Change Polygon Method, through one control line, the beach dune limit. On Mostardense beach, erosive rates were found along the coastline from 2005 to 2014. Mar Grosso beach showed variation with areas of dune development, between 2006 and 2015. Cassino beach had rather significant accretive rates, associated with high sedimentation and fluid mud deposit on the beach, from 2006 to 2015. Barra do Chuí beach showed accretive and erosive rates between 2003 and 2013; however, field evidence shows that this place has undergone an erosive process. The variation in the upper limit of the beach, beach dune limit, is more related to the action of events with high hydrodynamic energy which may erode frontal dunes, and recomposition to frontal dunas promoved by marine and eolian action. The results also showed the importance of locals characteristics in the context of the coastline variations.

Esse estudo visa caracterizar o comportamento do lençol freático na área urbana do balneário Cassino, Rio Grande do Sul, nos bairros Querência e Atlântico Sul. A partir de dados de altimetria do terreno (obtidos com GNSS-RTK), composição do solo, pluviosidade, GPR (Ground Penetration Radar) e medição da profundidade do lençol freático foram possíveis medir as diferentes profundidades da franja capilar superior e inferior do lençol freático e estimar as zonas com maior suscetibilidade a alagamentos. As posições de nível do lençol freático superficial obtido com GPR corroboraram com os valores medidos in situ através da escavação de poços de observação com uso de trado manual. O lençol freático apresentou um caráter superficial, com valor médio de 0,59 m de profundidade e aeração pouco espessa. Para o lençol freático profundo, o nível médio estimado foi de 1,37 m. Através da modelagem foi possível observar que o solo apresenta um maior índice de vazios nas regiões onde o lençol freático é mais profundo. Nas localidades onde o solo apresenta uma menor capacidade de absorção da água da chuva há uma maior suscetibilidade a alagamentos. A saturação do solo, como consequência o alagamento de uma região, ocorre quando o aporte de água corresponde ao volume livre do solo, que no caso da área de estudo, apresentou limiar de saturação na ordem de 108,78 mm. O conhecimento do comportamento do lençol freático é fundamental para que os gestores municipais disponham de ferramentas para o devido planejamento das localidades suscetíveis a alagamentos no balneário Cassino.

O presente estudo visa mostrar por meio de imagens de satelite e tecnicas de geoprocessamento, o comportamento da linha de costa estuarina do municipio de Rio Grande, entre a Avenida Major Carlos Pinto e a Rua Saturnino de Brito, nos anos de 2006, 2009, 2012 e 2016. A partir dos dados de linha de costa e da tecnica do Poligono de mudanca foi possivel detectar quais localidades apresentaram um processo de acrescao e/ ou erosao. O periodo entre 2006 e 2009 apresentou as maiores taxas de acrescao (1,78 m/ano), ao passo que as maiores taxas de erosao foram registradas entre os anos de 2009 a 2012 (0,85 m/ano). A partir do exposto tem-se que esse estudo pode vir a contribuir para o municipio, de forma que o uso dessas ferramentas auxilie na elaboracao e aplicacao de novas propostas de ordenamento para orla de Rio Grande.

Albuquerque, M., Espinoza, J., Teixeira, P., de Oliveira, A., Correa, I., Calliari, L., 2013. Erosion or Coastal Variability: an evaluation of the DSAS and the Change Polygon methods for the determination of erosive processes on sandy beaches. There has recently been growing concern about issues related to erosive processes on sandy beaches and climate change in the scientific community. Several methodologies have been proposed in the worldwide literature to quantify coastline retreat on shorelines in an accurate way. It has been questioned whether these methodologies show the erosive process or the shoreline variability in a certain area. From this perspective, this paper aims at characterizing the accuracy of the Digital Shoreline Analysis System (DSAS) and the Change Polygon Method in the studies of regression on shorelines which are prone to erosion. Data collected by a GPS-RTK along Hermenegildo Beach, located in the south of Brazil, and the geo-referencing of satellite images enabled the ou...