DEFINITION OF PHYSIOGRAPHIC UNITS IN THE SÃO FRANCISCO DE ASSIS MUNICIPALITY WITH GIS APPLICATIONS

Abstract

The physiographic compartmentalization is based on the elements of the environment that define the composition of the slopes (lithology and soils) and the shape (landforms). In this work, we used the elements of the environment combined with Geographic Information Systems and decision trees. The objective is to describe, classify and compartmentalize the municipality of São Francisco de Assis, located in the Southern Region of Brazil, in the western portion of the State of Rio Grande do Sul. It was determined eight physiographic units and six subunits: Unit Beluno, composed of two subunits represents 14.7% of the total area,  presents the busiest relief of the municipality; Chapadão unit, composed of two subunits, occupies 3.67%, formed by smooth relief between cliffs; Fluvial Valleys Unit with 10.32% of the area, occurs as ramps along the rivers Ibicuí and Jaguari; Cerros Unit represents the Plateau retreat, by erosive action and occurs in 1.51% of the area, with two subunits; Santa Rosa Unit marks the areas of springs in the Itu river basin, with an area of 6.95%; São Francisco de Assis Unit, with 50.23% of the area, is composed of four subunits, constituting a gentle relief of hills, with substrate is sandstone sedimentary rocks and sandy soils, sometimes generating sand fields; Serra dos Canários unit, with 5.77% of the area, is composed of two subunits, forming the areas at the highest altitudes of the municipality; Vila Kramer Unit, with 6.84% of the area, forming well developed soils with presence of clay due to alteration of the top portions with vitreous material of the volcanic spills. The work of compartmentalisation allows to understand the superficial processes and helps in planning works..