Physiographic compartmentation applied to the progressively detailed mapping of the urban center of Ilhabela, São Paulo State, Brazil

Abstract

The urbanization process in Brazil occurs mainly in a non-ordered way, without the proper consideration of the potentials and limitations of the physical environment, resulting in a form of urban development that may expose the population and the urban equipment to surface processes such as floods and mass movements. This has been observed in Ilhabela (São Paulo State, Brazil), where the high rates of population growth, combined with its rough topography, intensify this problem, highlighting the need of an adequate orientation to the urban expansion. In this context, the physiographic compartmentation based mapping may give us appropriate tools for the planning of orderly urban expansion in the physical environment. Therefore, the aim of this research was the mapping of the most densely urbanized area of Ilhabela, through the physiographic compartmentation based on the integrated analysis of aerial images. Photo analysis and photo interpretation, combined with field data, subsidized the division and classification of the study area in units that show similar morphological and geotechnical properties. This procedure resulted in the identification of units mapped at three scales (1:50.000, 1:20.000, 1:10.000), each with a different level of details, accompanied by the description of their main physical characteristics and main acting exogenous processes. The maps obtained allowed a detailed comprehension of the São Sebastião Island physical environment characteristics, as well as the main conditioning aspects of its human occupation, thus proving to be useful tools that are appropriate to the urban planning of the archipelago city.