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Tecnologias de Informação Geográfica no estudo de cheias/inundações e movimenntos de massas: o caso da Ilha de São Vicente, Cabo Verde
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As cheias/inundações e os movimentos de massas são fenómenos naturais que possuem um forte impacto nas populações constituindo, por isso, motivos de preocupações. Estes fenómenos, normalmente, desencadeados por precipitações extremas, podem ter consequências nefastas quando afetam aglomerados populacionais.
Neste sentido, a presente investigação tem como objetivo a aplicação dos Sistemas de Informação Geográfica (SIG) ao estudo das cheias/inundações e movimentos de massas, tendo como caso de estudo a ilha de São Vicente do arquipélago de Cabo Verde. Assim, através da utilização dos SIG procurou-se cartografar as áreas ou bairros possíveis de serem atingidos, pelas cheias/inundações e movimentos de massas, bem como a população afetada.
Recorreu-se à análise de notícias de jornais cabo-verdianos, assim como à exploração de entrevistas sobre a presente temática. Numa segunda fase, aplicou-se a técnica de análise multicritério em combinação com os SIG. Para auxiliar na atribuição dos pesos aos critérios utilizados na análise socorreu-se ao método Analytic Hierarchy Process (AHP). A presente investigação revelou que os bairros de Ribeirinha, Vila Nova/ Lombo Tanque, Ribeira Bote, Bela Vista/Pedreira e o centro da cidade destacam-se com risco elevado, uma vez que a se situam na convergência das linhas de água das principais bacias que drenam a metrópole e devido ao seu elevado número de residentes.
Realça-se a importância da extração de informação geográfica a partir do processamento digital de imagens de satélite para estudo de ocupação do solo e a sua integração em estudo de cheias/inundações e movimentos de massas. Através da abordagem píxel a píxel e orientada ao objeto, concluiu-se que a classificação ao nível do píxel, utilizando o classificador da Máxima Verosimilhança, produziu melhores resultados do que o classificador Bhattacharya. A imagem classificada no projeto deve integrar os Instrumentos de Gestão Territorial (IGT) da ilha, de modo a complementá-los e a enriquecê-los. Este complemento aos IGT é importante para prevenir eventuais situações de risco e perdas humanas ou materiais.
Flooding / floods and mass movements are natural phenomena which have a strong impact on populations and arise strong concern. These phenomena are usually triggered by extreme rainfall and may have adverse consequences when they affect settlements. In this sense, this research aims at the application of Geographic Information Systems (GIS) to study flood / flooding and mass movements, and using as a case study the island of São Vicente in the Cape Verde archipelago. Thus, through the use of GIS sought to map the areas or neighborhoods possible to be achieved, flood / flooding and mass movements, as well as the affected population. It appealed to the analysis of news Cape Verdean newspaper, as well as the exploitation of interviews on the subject present. In a second stage, was applied to multiple criteria analysis technique in combination with GIS. To assist in the allocation of weights to the criteria used in the analysis was used the method helped Analytic Hierarchy Process (AHP). This research revealed that the neighborhoods of Ribeirinha, Vila / Lobo Tanque, Ribeira Bote, Bela Vista / Pedreira and the City Center stand out with high risk, since they are in the convergence of streams of the main basin that drain the city and due to its high number of residents. It is important to emphasize the relevance of geographic information extraction from digital satellite imagery for land use study process and their integration into study of flood / flooding and mass movements. Through pixel to pixel-oriented approach to the object, it was found that the classification level of the pixel using the Maximum Likelihood classifier, produced better results than the classifier Bhattacharya. The classified image in the project should integrate the Territorial Management Instruments (IGT) of the island, in order to supplement them and enrich them. This addition to the IGT is important to prevent any risk situations and human or material losses.
Flooding / floods and mass movements are natural phenomena which have a strong impact on populations and arise strong concern. These phenomena are usually triggered by extreme rainfall and may have adverse consequences when they affect settlements. In this sense, this research aims at the application of Geographic Information Systems (GIS) to study flood / flooding and mass movements, and using as a case study the island of São Vicente in the Cape Verde archipelago. Thus, through the use of GIS sought to map the areas or neighborhoods possible to be achieved, flood / flooding and mass movements, as well as the affected population. It appealed to the analysis of news Cape Verdean newspaper, as well as the exploitation of interviews on the subject present. In a second stage, was applied to multiple criteria analysis technique in combination with GIS. To assist in the allocation of weights to the criteria used in the analysis was used the method helped Analytic Hierarchy Process (AHP). This research revealed that the neighborhoods of Ribeirinha, Vila / Lobo Tanque, Ribeira Bote, Bela Vista / Pedreira and the City Center stand out with high risk, since they are in the convergence of streams of the main basin that drain the city and due to its high number of residents. It is important to emphasize the relevance of geographic information extraction from digital satellite imagery for land use study process and their integration into study of flood / flooding and mass movements. Through pixel to pixel-oriented approach to the object, it was found that the classification level of the pixel using the Maximum Likelihood classifier, produced better results than the classifier Bhattacharya. The classified image in the project should integrate the Territorial Management Instruments (IGT) of the island, in order to supplement them and enrich them. This addition to the IGT is important to prevent any risk situations and human or material losses.
Descrição
Palavras-chave
cheias/inundações mass movements movimentos de massas floods / flooding Sistemas de Informação Geográfica Geographic Information System deteção remota Remote Sensing São Vicente Saint Vincent Cabo Verde Cape Verde