PAISAGENS INSULARES DO CEARÁ: distribuição geográfica e caracterização estrutural nas bacias Metropolitana, Curu e Médio Jaguaribe (insular landscapes of Ceará: distribution and structure in basins metropolitana, Curu and Médio Jaguaribe)
Abstract
A construção de açudes perenes no Nordeste Brasileiro acionou a fragmentação da paisagem, criando paisagens insulares lacustres ou ilhas artificiais. O Ceará é detentor de inúmeras ilhas artificiais e o presente trabalho determinou o número, distribuição e localização geográfica delas nas bacias Metropolitana, Curu e Médio Jaguaribe, bem como as caracterizou estruturalmente quanto ao tamanho, forma e grau de isolamento. Imagens de açudes com ilhas receberam vários tratamentos tendo sido gerado mapas com legendas contendo espelho d’água e ilha(s). Em cada mapa foi aplicado o software Fragstats. Dos 40 açudes públicos analisados 21 ou 52,5% do total, apresentaram pelo menos uma ilha. O total de ilhas levantadas nas três bacias hidrográficas foi de 201. A localização geográfica das ilhas nos açudes foi predominantemente aleatória. A ilha de menor área coube a de número 5 do açude Caracas com 0,005 ha e a maior ficou representada pela de número 2 do açude General Sampaio com 27,238 ha. Todas as ilhas apresentaram forma não circular. A ilha mais remota foi a de número 11 do açude Pacoti com 943 m e a mais próxima a de número 3 do açude Caracas com 3 m.
Palavras chave: paisagem insular, ilha artificial, açude, fragstats.
ABSTRACT The construction of perennial dams in Northeast of Brazil set in action the fragmentation of landscapes, producing insular landscapes or artificial islands. The State of Ceará possesses a significance number of them and the present work determined number, distribution, geographic localization of lake islands found in basins Metropolitana, Curu and Médio Jaguaribe, and characterizing each of them regarding to size, shape and degree of insulation. Images from selected dams were used to plot maps containing water covered areas and island(s), and then FRAGSTATS software was applied to analyze each map. From 40 public dams studied, 21 (52,5%) showed at least one island. A total amount of 201 islands were countered. It was observed that islands were randomly located inside the area covered by dams. The smallest island was the number 5 of dam Caracas with 0.005 ha, whilst the biggest one was number 2 of dam General Sampaio with 27.238 ha. All studied islands showed non-circular shape. The most distant from margins were islands number 11 of dam Pacoti with 943 m, whilst the closest to margins were island number 3 of dam Caracas with 3 m.
Key words: insular landscape, artificial island, dam, fragstats.
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