GIS applied to determine environmental impact indicators made by sand mining in a floodplain in southeastern Brazil

Since the late 1940s sand mining has been developing in the Paraiba do Sul River, especially in its floodplain. Today, sand extraction exceeds 15 million tons per year causing the relevant environmental problems. To examine the evolution over a 35-year time span of these environmental impacts, land cover data from a 31-km(2) floodplain were compiled from large-scale vertical aerial photographs from 1962, 1986/1988, and 1997/1998. These data were analyzed using a geographical information system (GIS). A number of environmental impact indicators were identified and measured through the application of aerial photo/GIS methodology. These include (1) total mining areas, (2) former agricultural land converted into open pits, open water ponds and mining ancillary installations, (3) deforested areas, (4) channel river morphology modification, (5) vegetation growth in reclaimed areas, and (6) mining encroachment on the legally protected riverside zone. Most indicators show a great increase in impact magnitude over the period.