MODELADO DO RELEVO E POTENCIAL DE FRAGILIDADE À EROSÃO NO ESTADO DO RIO GRANDE DO SUL

Abstract

The exploitation of environmental resources consumes thelandscape when it generates impacts that cause its degradation. Theknowledge of the natural fragility of a place allows to evaluate thedegradation risks that an atmosphere can suffer and it also makes possibleto know the degree of tolerance that certain atmosphere can support. TheState of the Rio Grande do Sul is constituted by the provincesgeomorphologic denominated by Ross (2005) as Plateaus and Plated ofthe Basin of Parana, Outlying Depression Sul-rio-grandense , Plateau Sulrio-grandense , Plain of Lagoa dos Patos and Lagoa Mirim . The territorywith that group present many relief forms and different types of soilsconverging for different fragility degrees. In that perspective the work hasas objective the determination and the cartographic registration, in the stateof Rio Grande do Sul, of areas with different degrees of natural fragilitystarting from the topographical resignation given by the modeled of therelief. The methodological procedures were based on the conception ofEUPS (Universal Equation of Losses of Soil) being taken as reference thetopographical factor (LS) through the rising of the modeled of the relief,obtained from the methodology proposed by Ross (1994). The factor K(erosion degree of the soil) had as reference the rising of recognition ofthe soils of the State (Brazil, 1973). The factor R (erosion degree of therain) was considered as a constant variable. The factor consideredextenuating, (C, P) were omitted the use of the earth and handling practices.The rising of the potential of natural fragility was obtained in atmosphere of SIG (System of Geographical Information) through the crossing of themap of modeled of the relief and of the map of soils. The classes fordefinition of the potential of natural fragility were contained through thetechnique of the deviation quartiles (Gerardi & Silva, 1981). The obtainedresults show the prevalence of the modeled of the relief with weak dissectionin the State, mainly in the North portion (Plateaus and Plated of the Basinof Parana) and significant occurrences in the Southeast (Plateau Sul-riograndense).The medium dissection is shown predominant in the PlateauSul-rio-grandense. The strong dissection and very fort has prevalence inthe northeast area of the State (Plateaus and Plated of the Basin of Parana).The flattening areas locate at the area West of the State (Plateaus and Platedof the Basin of Parana) and the accumulation areas prevail in the OutlyingDepression Sul-rio-grandense and Plain of Lagoa dos Patos e Lagoa Mirim.The obtained map, considering the work scale adopted, shows therelationship of the modeled of the relief with the provinces geomorphologic.The fragility potential, expressed in the geographical distribution of theprovinces geomorphologic illustrates the different degrees of naturalfragility in Rio Grande do Sul.