Mapping alluvial areas in semi-arid region of Brazil through collateral data and satellite images/Mapeamento de areas aluvionares no semiarido brasileiro por meio de dados colaterais e imagens orbitais

The semi-arid region of Brazil has great potential for storing water in alluvial areas, and may give support to small-scale family farming. There is a need to establish a methodology for mapping these areas with the objective of future studies to implement underground dams and suitable management of the soils that occur on alluvial terraces. In this way, the aim of this study was to apply Landsat-Thematic Mapper images together with collateral data such as the drainage network, map of soil classes and elevation data to assist in the classification of alluvial terraces. The study area was Pajeu River basin located in the 'Caatinga' ecosystem of the Pernambuco state. Topographic assessment of the alluvial areas was done by using SRTM (Shuttle Radar Topography Mission) data. It was found that the single use of orbital data brings incongruous classification, but with the inclusion of collateral data it was possible to obtain better results in classification. The drainage network was also important in masking the spurious classification. The analysis of the topography of the classified areas was inadequate using SRTM data. Key words: alluvial soils, supervised classification, remote sensing, relief A regiao semiarida do Brasil possui grande potencial para armazenamento de agua em areas aluvionares, podendo potencializar a pequena agricultura. Verifica-se a necessidade de uma metodologia para mapeamento dessas areas, com o objetivo de futuros estudos in loco para implantacao de barragens subterraneas e manejo correto dos solos aluvionares. Neste sentido, objetivou-se a aplicacao de imagens Landsat- Mapeador Tematico 5 em conjunto com dados colaterais, como a rede de drenagem, mapa de classes de solo e mapa de relevo para auxiliar na classificacao de terracos aluviais. Teve-se, como area de estudo, a bacia do Rio Pajeu, no sertao do estado de Pernambuco. Buscou-se tambem, por meio de dados SRTM (Shuttle Radar Topography Mission), a avaliacao topografica das areas classificadas. Verifica-se que a utilizacao unica de dados orbitais traz classificacao incongruente mas com a insercao de dados colaterais e possivel obter melhores resultados na classificacao. A rede de drenagem e fundamental no mascaramento de classificacoes espurias. Quando procede a analise topografica por meio de dados do SRTM das areas classificadas como terracos aluvionares, observa-se a inconsistencia desses dados. Palavras-chave: solos aluviais, classificacao supervisionada, sensoriamento remoto