Multitemporal analysis of land covering and vegetation areas under quaternary superficial formation - a study of the hydrographic basin stream Puitã, Rio Grande do Sul - Brazil

Abstract

The hydrographic basin of stream Puitã, located in the southwest of the state of R Grande do Sul - Brazil, is characterized by quaternary superficial formation. The formations are dominated by erosive features and sand strands located in the geologic compartment of hills as well by bushes located on the hillside and ciliary's bushes locate along the course of the water together with the campestre vegetation. The use of the lan stands out with plots of land used to agriculture, intensified in the last decades. Th agricultural activities left the soil fragile, causing erosive features. This study aims to identi he existent relationship between the type of vegetation and the soil degradation in the regio of the hydrographic basin. The methodology is based on digital classification of Landsat-T satellite images, data acquired between 1984 e 2004, on the correlation analysis betwee degraded areas, classes of land use and vegetation's types. The results showed thematic maps that allowed identifying the different fragilities an susceptible areas to the sandification process. The multitemporal approach allowed evaluate the modifications of the mapping classes and to identify the expansion or retractin of sand strands and erosive processes. It was detected that the agricultural use is th responsible agent for the amplification of the soil fragility.