Urban expansion and land use/land cover changes in Canoas municipality (Rio Grande do Sul) between 1984 and 2014.

Abstract

Canoas, a municipality at the metropolitan region of Porto Alegre, RS, Brazil registered a vertiginous population growth throughout the 20th century, mainly based on precarious allotment on unsuitable areas. The objective of this study was to evaluate the urban expansion process that took place in the municipal territory of Canoas between 1984 and 2014. Five land use/land cover (LULC) maps were developed by means of visual interpretation on Landsat 5 and 8 satellite images. Altogether, ten classes were identified. A cross-tabulation matrix as a result of a pairwise overlay of the LULC maps allowed to calculate the areal extent and proportion of detected transitions. Results show strong contrast between Canoas’ east and west side. The sectors are separated from each other by a highway which at the same time separates and stimulates the urban development. Between 1984 and 2002, the urban expansion followed an informal way, mainly by native vegetation suppression or conversion of agriculture and silviculture areas into urban ones. During the period 2002 and 2014 Canoas experienced a less intense urban growth which occurred mainly over grassland and bare soil areas. But in the period we recorded and expansion of forests and wetlands. We conclude that most of the land still available to urbanization in Canoas on areas susceptible to flooding.