This work aimed to evaluate deforestation, relating it to different classes of slope in the municipality of Ibirubá, RS. Four thematic maps were developed, one with declivity classes and three with forest areas, corresponding to the periods of 1956, 1965 and 1975. The map of the declivity classes was based on the classification map of soils of the municipality and on determinations of slopes by aerial photographs. The forest maps were made using aerophotogrammetric coverage of the three dates cited. The results found, for the original zone of forest, revealed that deforestation started with greater intensity in the class of 8 to 15% of slope. Although the class of 2 to 8% offered topographic conditions to agriculture, it remained the main forest reserves, coinciding with the farms' fund. These reserves gradually gave way to agricultural occupation, especially in the period 1965 to 1975. In classes of declivity of less than 2 and above 15%, there was less deforestation due to topographic conditions because they are lands subject to flood or very steep. In the original field zone, deforestation was present on all declivity classes, with higher intensity where topographic conditions favored agricultural occupation, that is, in the declivity class of 2 to 8% and in the 8 to 15% class. In classes of slope less than 2 and above 15% there was less deforestation due to topographic conditions because they are terrains subject to flood or very steep. In the original field zone, deforestation was present on all declivity classes, with higher intensity where topographic conditions favored agricultural occupation, that is, in the declivity class of 2 to 8% and in the 8 to 15% class. In classes of slope less than 2 and above 15% there was less deforestation due to topographic conditions because they are terrains subject to flood or very steep. In the original field zone, deforestation was present on all declivity classes, with higher intensity where topographic conditions favored agricultural occupation, that is, in the declivity class of 2 to 8% and in the 8 to 15% class.
