Application of image of the satelite Landsat TMS and of vertical aÃrias photographs for the mapping of coastal reefs and analysis of the littoral physical processes related - TAMANDARÃ, PE, BRAZIL / AplicaÃÃo de imagem do satelite Landsat TMS e de fotografias aÃrias verticais para o mapeamento dos recifes costeiros e anÃlise dos processos fÃsicos litorÃneos relacionados - TAMANDARÃ, PE, BRASIL

DamÃsia Carla Cunha Lima

The coastal area is one of the most complex and sensitive environments of nature, presenting great ecosystem diversity, coral reefs among them, and is widely recognized to be approaching a critical situation. The modern expressive urban occupation of coastal areas all over the world causes great pressure and marked alterations to these environments. The present work aims to accomplish the mapping of the coastal reefs of TamandarÃ, Pernambuco - Brazil, using images of the Landsat TM5 satellite and vertical aerial photography, as well as the analysis of coastal physical processes related to the presence of those reefs. The following mapping classes were considered: mapped reefs from satellite imagery and mosaiced aerialphotography, by photo-interpretation processes, mapped reefs from GPS, and traveled channels. Starting from remote sensing images with different spatial resolution, it was observed that, in spite of supplying a richer visual interpretation of colors and textures, the Landsat image had more limited spatial resolution, generating a map-image compatible with the 1:50.000 scale. Aerial photography, despite of being a monochrome product, allowed satisfactorily for more detailed mapping, resulting in a map-image compatible with the 1:10.000 scale. Joining the best of each technique, major spectral resolution in satellite imagery and major spatial resolution in verticals aerials photographs, through the fusion between the two products, resulting in a map-image in the 1:10.000 scale, with much information. The photo-interpretation process adopted for reef mapping responds satisfactorily to the purpose, with a precision value equal to 82,19%. Such precision however, is determinated from the average of the areas mapped by photo-interpretation, being thus relative. The process of walking the borders of the emerging reefs with a GPS turned on, in the averaging function, at fixed tide levels of about +10cm in relation to the mean sea level, proved to be satisfactory both to supply data at the beginning of the work â satellite imagery geo-referring â and to defining exposed reefs areas. Regarding coastal physical processes, it was possible to confirm alterations in the pattern of waves and currents caused by the presence of the reefs. Such presence is directly related to sandy strip width and shown to be one of the main factors leading to smaller erosional susceptibility, also being a conditional factor for local geomorphology. Starting from the results of this study, environmental management can be accomplished with better cartographic precision, e.g., the delimitation of areas of temporary impediment for fishing, establishing "nurseries", and areas of free fishing, thus increasing local biodiversity and causing other environmental benefits.

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