Use of Geographic Information System for ranking degraded areas for residual soil - saibro - exploitation, Ubatuba, SP, Brazil

Abstract

The Municipality of Ubatuba (northern coast of São Paulo, SE Brazil) contains 116 sites degraded by mining activities, which were assessed and classified by means of a Mineral Exploitation Index. The Index is based on GIS operations and takes into consideration topographic variables as well as legal variables and land use restrictions. Its application classified six sites as very highly potential for exploitation and 35 as highly to moderately potential. In the first phase of assessment, the volume of bulk material available was calculated semi-automatically using a computer routine present in the SPRING GIS package. This was followed by the application of criteria for the adjustment of bulk volumes, such as a) changes in the topographic geometry and b) numerical scores related to legal and land use restrictions, which were attained through GIS topological operations. The results were sorted into five numerical interval classes that express priorities for the exploitation of residual soil (saibro) based on its mineral potential. The outcomes are thought to be useful in two ways: a) for devising technical and financial schemes for site reclamation; b) for responding to the local demand for construction materials without having to initiate new mining sites in areas that should be preserved instead.