Distribuição e classificação de voçorocas por meio de indicadores morfométricos em sub-bacias no município de Cacequi - RS

Abstract

The southwest region of the state of Rio Grande do Sul is one of the areas where erosion processes by gullies occur, linked to the geological / geomorphological aspects, and in their genetic context they present particularities determining to the installation of such processes. In this context, the present research sought to understand the geographic distribution of occurrences of gullies in a sample area in the municipality of Cacequi. The analysis was based on the results referring to the morphometric indicators that made it possible to classify them in relation to their forms, in addition to understanding their levels of evolution and development, using as a unit of analysis the sub-basins present in the central portion of this municipality, where 298 gullies events were identified and mapped. This procedure took into account the morphometric attributes (area, perimeter, width, depth, volume, circularity index, hypsometry, slope, slope shapes, profile and plane curvature, slope orientation, slope lengths and fault geological fractures). The methods used in the research were based on the qualitative and quantitative analysis of the data on the morphometric properties, which were submitted to the statistical analysis, allowing to establish the correlation between the data and the similarity of the sub-basins, besides the application of the Method of Informative value to determine the physical attributes that contribute most to the development of the erosive process in question. The map of the gullies distribution indicated the patterns of the different forms of gullies, allowing their classification by analyzing the morphometric indicators, allowing identifying in the area six different forms of gullies (Linear, Bulbiform, Branched, Mixed Irregular, Rectangular and Irregular Rectangular). The lineaments mapped in the orientation of the gullies showed predominance in the east-west and northeast-southwest orientation, fact that evidences the influence of the structural control in these processes and the main directions of the gullies contribute in their forms. Finally, the obtained results allowed proposing a scenario of how the systematic development of the different forms of gullies occurs in this part of the Peripheral Depression in the State.