Different methodological approaches to natural vulnerability to erosion in southeastern Brazil

The natural vulnerability addresses the processes of morphogenesis and pedogenesis integrating information related to the rocky substrate, soils, geomorphology, vegetation. The study of natural variability is essential for understanding ecosystems in the face of change processes in the environment. This work aimed to analyze the natural vulnerability to the occurrence of erosion, adopting a method based on Crepani and Analysis Hierarchical Process (AHP) method in the Rio Claro Watershed - São Paulo - Brazil. Four information plans were used in the 1: 50000 scale, being: geomorphology, pedology, geology and vegetation / anthropic intervention. The Natural Vulnerability to Erosion Chart is classified into five classes (Very Low, Low, Average, High, and Very High). Comparing the charts generated by the two methods based on Crepani et al. (2001) and Saaty (1980), there was a difference in the Very Low and High vulnerability classes. The most evident class in both charts is the average vulnerability, corresponding 94.55km² of the area in Crepani Method chart, and 93.34km² in AHP Method chart, followed by the “Low” class corresponding of 55. 56km² and 76.67% respectively the Crepani and AHP methods. For the "High" class there was a decrease of 48.28% when compared to the two cards, the "Very high" class suffered the least change (-0.09%), while the "Very low" class increased above 100%. The methods employed allowed the generation of results that show the reality of the study area, it is worth mentioning that the Crepani method is more generic because it considers the similarity of the information plans for the vulnerability analysis, whereas the AHP method presents the advantage of hierarchizing both information plans and their classes, highlighting the relative importance of natural vulnerability to erosion. the "Very high" class suffered the least change (-0.09%), while the "Very low" class increased above 100%. The methods employed allowed the generation of results that show the reality of the study area, it is worth mentioning that the Crepani method is more generic because it considers the similarity of the information plans for the vulnerability analysis, whereas the AHP method presents the advantage of hierarchizing both information plans and their classes, highlighting the relative importance of natural vulnerability to erosion. the "Very high" class suffered the least change (-0.09%), while the "Very low" class increased above 100%. The methods employed allowed the generation of results that show the reality of the study area, it is worth mentioning that the Crepani method is more generic because it considers the similarity of the information plans for the vulnerability analysis, whereas the AHP method presents the advantage of hierarchizing both information plans and their classes, highlighting the relative importance of natural vulnerability to erosion.