Erosão Costeira em Praias Adjacentes às Desembocaduras Fluviais: O Caso de Pontal de Maceió, Ceará, Brasil. (Portuguese)

Coastal Erosion of Beaches near River Mouths: The Case of the Pontal de Maceió, Ceará, Brazil. (English)

FORTALEZA (Brazil); BRAZIL

This article aims to analyze the relationship of the erosion process with the dynamics of the river Jaguaribe, and the consequent depreciation of buildings and decline of leisure activities on the beach of Pontal de Maceio, in the Town of Fortim, in the costal state of Ceará, Brazil. Inserted in the valley of the Jaguaribe River, one of the most important basin in the hydrological and historical context in the state of Ceará, it is the only option for leisure of ocean beaches in the city of Fortim, attracting close to 4,000 visitors per year. The natural beauty, the shallow water and calmness in tidal flats, the local cuisine, the bucolic atmosphere and the proximity of Fortaleza, the capital of Ceará State, are the main attractions for tourism. The water deficit and the changing of social space and occupation within the drainage areas over the last 40 years have affected the evolution of the adjacent coastal area. Among the impacts we can enumerate a large number of dam construction of large and small sizes, deforestation of gallery forests and silting. To assess the erosion evolution and its impact on historical, social and economic of the dwelling houses and buildings, the data from reservoirs regulated and settled spilling flow were correlated with the shoreline retreat rates in order to assessing the interdependence between these two variables. The shoreline retreat rate has been calculated based on past studies and surveys of beach morphology in the period 2001 to 2006. To validate the information, calculations of setbacks, obtained by techniques of Geographic Information System (GIS) of aerial photographs and satellite images, were used. This same technique was used to obtain the number of buildings located in sedimentary features important to the coastal sediment balance. Researches on the evolution of the values of enterprises, infrastructure, tourism, leisure activities and the perception of the local analysis on the impact of erosion on the property devaluation were held in public agencies and in the field through the application of questionnaires. Among the observed results stands out the decreasing flow of the Jaguaribe River and consequent increase in the rate of retreat to the shoreline from 17 meters per year to 29 m / year soon after the operation of Castanhão Dam has been set. During that period, tents, barracks and bars in the strip of beach were away 100m from the line in the water. But the lack of adequate management, such as the construction of stalls and restaurants in masonry and absence of drainage system of rainfall waters favored the return of erosive processes. Part of backshore in the Fortim town urban core is occupied by constructions and buildings making the sediment balance difficult in this sector. … [ABSTRACT FROM AUTHOR]

Esse artigo tem por objetivo analisar a relação do processo erosivo com a dinâmica do rio Jaguaribe e a conseqüente desvalorização dos imóveis e declínio das atividades de lazer na Praia de Pontal de Maceió, no Município de Fortim, na costa leste do Estado do Ceará-Brasil. Inserida no vale do Rio Jaguaribe, uma das mais importantes bacias hidrográficas, no contexto hidrológico e histórico no Estado do Ceará, representa a única opção de lazer em praias oceânicas no Município de Fortim, atraindo cerca de 4.000 visitantes/ano. A beleza paisagística, as águas rasas e calmas nos baixios de marés, a cozinha regional, o clima bucólico e a proximidade de Fortaleza são os principais atrativos ao turismo. O déficit hídrico e as transformações sócio-espaciais no interior da bacia de drenagem nos últimos 40 anos repercutiram na evolução da zona costeira adjacente. Para avaliar a evolução da erosão e seu impacto no valor histórico, social e econômico dos imóveis foram correlacionados os dados de vazão regularizada dos reservatórios com as taxas de recuo da linha de costa para avaliar a interdependência entre essas duas variáveis. As taxas de recuo da linha foram calculadas baseadas em estudos pretéritos e levantamentos da morfologia praial no período de 2001 a 2006. Para validação das informações foram utilizados cálculos de recuos obtidos por técnicas de geoprocessamento em fotografias aéreas e imagens de satélites. Esta mesma técnica foi utilizada para obtenção do número de imóveis localizados em feições sedimentares importantes para o balanço sedimentar costeiro. Pesquisas sobre a evolução dos valores dos empreendimentos, infra-estrutura turísticas, atividades de lazer e análise da percepção dos locais sobre o impacto da erosão na desvalorização dos imóveis foram realizadas nos órgãos públicos e em campo com a aplicação de questionários. Dentre os resultados observados destacamse a diminuição da vazão do rio Jaguaribe e conseqüente aumento da taxa de recuo da linha de costa de 17 m/ano para 29 m/ano após o funcionamento do Castanhão. … [ABSTRACT FROM AUTHOR]

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