Aplicação de geotecnologias na análise dos impactos ambientais nos imóveis rurais localizados na Bacia Hidrográfica do Rio Doce quanto ao desastre do rompimento da Barragem de Fundão em Mariana/MG

Abstract

On November 5, 2015, what is currently classified as the largest environmental accident in history in Brazil was recorded, the rupture of the mining tailings deposit contained in the Fundão dam, located in Bento Rodrigues, district of Mariana in the state of Minas Gerais. This tailings deposit is managed by Samarco Mineração S. A., representative and subsidiary of an international consortium of Vale S. A. and BHP Billiton. This environmental accident gained due importance due to its direct consequences, where it is worth mentioning the total destruction of the urban area of the Bento Rodrigues district, the loss of nineteen human lives and the silting of the Gualaxo do Norte, Carmo and Doce rivers, such as their pollution. However, the chain of indirect consequences, depending on the type and form in which the waste was found, as well as the means of dispersion favored by the local hydrographic dynamics, led in its indirect form to a potentialization of environmental, economic and social damage, as the dynamics of the watershed directly influenced the dispersion and evolution of the problem, while leading the flow of mud along the gutter of rivers located downstream of the accident point. The present research, through the application of geotechnologies in its analyzes, establishes a division in the study area into two regions, the one directly affected by the mud rejection in the suppression of the areas where it advanced on the ground (Region 1: dam breaking point to the Risoleta Neves HPP spillway, covering the Gualaxo do Norte, Carmos and Doce rivers), with an area of 52162.46 hectares in this region and a total of 308 properties (rural properties) affected by the accident. Region 2 has an area of 237135.12 hectares and a total of 762 properties located on the banks of the Doce River (from the Risoleta Neves HPP spillway until reaching its mouth in the Atlantic Ocean) where the main environmental aggravating factor was contamination. Through the elaboration of land use and land cover maps, it accounted for Region 1 a total of 1999.92 hectares of area affected by tailings mud, of which 76.5% resulted in direct losses to rural properties registered in CAR. Also identifying for the municipalities of Mariana and Barra Longa the properties that suffered direct damage, presenting these losses to the values of: Permanent Protection Area, 821.06 ha; Consolidated Area, 429.41 ha; Legal Reserve, 141.56 ha; Native Vegetation: 275.70 ha. Through the use of the FragStats 4.2 software, a quantification of geospatial landscape metrics was performed, showing as results, indices corresponding to areas suitable for natural recovery. SHDI and SHEI shape indices were calculated, showing 1.01 and 0.46 respectively, indicating the predominance of fragments with simple shapes and the edge density indices, with 33.57 and 2.03 format, which in turn reinforce a pattern in a simplified manner with little edge effect around it. The use of public geospatial data proves to be effective in landscape analysis and guiding actions after spatial analysis and pre- and postdisaster events regarding correct decision making and activities to be performed in an impacted environment.