Certain parts of the ground surface of South Africa are prone to sudden, catastrophic collapse, which may lead to death, injury or structural damage. Such features are known as sinkholes and in South Africa they occur in areas underlain by dolomite rock. This poses a potential risk to the safety of many people and the structures in which they work and live. Given sufficient time and the correct triggering mechanisms, instability may occur naturally but is expedited many orders of magnitude due to man’s activities. The primary triggering mechanisms in such instances include:
- The ingress of water from leaking water-bearing services;
- Poorly managed surface water drainage; and
- Groundwater level drawdown.
Approximately 25% of the Gauteng Province, as well as parts of Mpumulanga, Limpopo, North West and Northern Cape Provinces, are underlain by dolomite. Sinkholes have over the past 50 years been the direct cause of death of at least 39 people in South Africa. Sinkholes not only cause damage to developments and infrastructure, their remediation costs are also high. An estimated cost of the damage caused by sinkholes to date is in excess of R1, 3 billion.
The report by Oosthuizen and Richardson 2011 discusses the mechanisms and consequences of sinkhole and subsidence formation and the areas affected in South Africa.
Oosthuizen, A.C., & Richardson, S. 2011. Sinkholes and subsidence in South Africa. Council for Geoscience Report number: 2011-0010.