The main supply of new sand to the beaches of KZN is derived from riverine sources via its 77 estuaries. Interrupt the supply of sand and beach nourishment, suddenly beaches fade and disappear. Port cities such as Durban know only too well what happens when the natural supply of sand to their beaches is compromised.
However, the construction industry values this supply of clean sand, and often “mine” their sand from environmentally vulnerable estuaries. Sand mining is largely driven by demand for development of houses and associated infrastructure.
Sand mining is a consumptive activity that results in a net decrease in the resource, such that less sand may be available for coastal replenishment and hence other, often non-consumptive, uses such as recreation and tourism. A number of estuaries are now under threat from sand mining activities.
Sand Mining in Estuaries
Estuaries are one of the most important ecosystems found within the coastal zone. Estuaries are known for their high levels of biodiversity and services, such as nursery areas for fish, shrimps and crabs, as well as feeding and roosting sites for waders and other migratory birds.
A study in 2007 showed that there were approximately 60 sand mining operations within 18 of KZN’s estuaries; predominately occurring in the bigger systems. The number of operations occurring on a single system varied, from a single operation on the Thukela to 10 on the Mvoti Estuary. A previous study, done in 2003, showed that the total mining volume for all KZN estuaries was approximately 742 900 m per annum, split across 14 systems in the Province. Of concern is that sand mining activities have an adverse effect on estuarine and river functioning through the depletion of sand.
Effects of Sand Mining on the Shoreline
Effects of sand mining can be much further reaching than the immediate habitat, whereby the quantity of sand that reaches the coast is negatively affected. This affects coastal stability and functioning of beaches. Sandy beaches are identified as critical for a range of socio-economic reasons, with direct benefits from eThekweni sandy beaches being estimated at R 113 596 667 per km, through value for recreation, tourism and aesthetics. In addition, indirect benefits were valued at R 915 000 per km for factors such as erosion control, biological control, habitats and existence value. Depletion of sand instream and at the coast can result in alterations to estuarine mouth functioning, the effects of which are compounded by sea-level rise and coastal erosion.
In some cases sand mining can in turn lead to damage of infrastructure and properties, through the undercutting of banks, increased erosion and a change in the carrying capacity of the stream.
Sand mining in KZN estuaries has an adverse effect on both estuarine and coastal functioning, having contributed to the reduction of natural buffers, predisposing sections of the coastline to damage from increasingly variable seas and storm surge events. Impacts on the biological function of estuaries have also been recorded. While the need for building material is unquestionable, other terrestrial sources of sand should be preferred. Moreover, estuarine sand mining should be better and more wisely managed by the permitting authority, the Department of Mineral Resources, in order to halt a cascade of negative environmental effects.