Mining activities in South Africa over the past 120 years have changed the natural environment in several ways. Current challenges for mining companies lie in rehabilitation and prevention of further environmental degradation. One particular area of concern is surface deformation associated with mining activities, particularly mining subsidence.
Mining subsidence associated with underground coal mining is, a gentle, gradual settling of the earth’s surface. Underground mining cavities can result in a lowering of the earth’s surface (surface subsidence) as a result of the collapse of bedrock and the subsequent sinking of unconsolidated surface sediments (Perski & Jura 2003). The effects of surface subsidence on the built environment are severe and include damage to infrastructure (roads, dams, pipelines and buildings). The effects of surface subsidence on the natural environment include the alteration of hydrological pathways. The ponding of water in subsidence basins results in an increase in groundwater recharge. The groundwater circulating through mining cavities becomes polluted and discharges into the natural environment contaminating wetlands, streams and dams.
The report by Heath and Engelbrecht (2011) describes the surface deformation features associated with mining activities in two case-study areas: gold mining activities in the Witwatersrand gold fields and coal mining activities in the Witbank coalfields.
Heath, G., & Engelbrecht, J. 2011. Deformation due to mining activities. Council for Geoscience Report Number: 2011-065.