MORPHOMETRIC STUDY OF CONTROLS TO EROSIONAL FEATURES AND IDENTIFICATION OF AREAS SUSCEPTIBLE TO MASS MOVEMENT HAZARDS IN THE CONTAGEM WATERSHED, DISTRITO FEDERAL

Abstract

This work aims to create a morfometric analysis oriented to the catchment on the Contagem Basins/DF. We are trying to identify rates of erosion susceptibility from a hydro-geomorphologycal map proposal. The map were generate crossing the drainage efficiency index (DEI) and the morphological map (slope and curvature). We used the ArcMap 9.3 SIG to build Maps and create datas to made tables and graphs. Second order catchments have DEI (km/km²) values from 0,04to 18,56, with 4,51 of average. Third order catchments have values from 0,04to 18,56, with 2,48 of average. Near 80% of the features mapped by Braga (2012) were in the areas of DEI, because that map has covered the slope process mainly. The curvature map shows the concentration of the erosive features on the concave slopes, despite the fact that there are a majority of convex features, confirming expectations about the correlation of erosion and flow concentration. The hydro-geomorphological map showed areas of erosive susceptibility emphasizing the possible landslides areas. There are a low erosion potential in average, despites the fact that 49% were divided in medium and high erosion potential, which was not expected to a basin in Brasília. Landslides were observed in fieldworks, even if they have not been systematically mapped. The next steps of the work in the Contagem basin will focus on the landslides mapping and geotechnical resistance of the material.