White sand, bare bottoms under threat
IT is famous for its white sand and bare bottoms, but for how much longer?
Picturesque Sandy Bay, better known as a nudist mecca, is one of several Cape beaches fast running out of sand as human activity disrupts natural sand flow around the peninsula.
Now a team of scientists is conducting underwater seismic tests to find out what is happening — and whether anything can be done.
The problem has also prompted an unusual emergency sanddump plan in Hout Bay, where the city council plans to transport 25 000 cubic metres of sand to a ridge above Sandy Bay in the hope that the wind will blow it to the beach.
Sandy Bay’s normal sand supply — a wide dune belt linking it to Hout Bay beach — has mostly disappeared under housing development. Instead, the sand now builds up in Hout Bay with nowhere to go.
The council confirmed the emergency sand intervention this week.
“We are about to begin the trucking of sand from Hout Bay beach up to the Nek,” said Garreth Bloor, city mayoral committee member for economic, environmental and spatial planning.
‘‘The purpose is to reduce the sand bulk on Hout Bay beach, but as a second component we will assess whether the sand is transported into Sandy Bay.
“The reality is, however, that due to extensive urbanisation and development in Hout Bay, the historical sand-transport system has been irrevocably changed. And, as a result, Sandy Bay will have less sand, which is evident in photographs from the 1930s,” Bloor said.
The plan was unlikely to have an immediate impact, “but we will assess it as the project unfolds”, he said.
Environmentalists say the crux of the problem is the development of housing on key sand-dune pathways that act as conveyor belts of sand moving from one beach to the next. Without these dune passageways, the sand cannot move freely and piles up.
There is also mounting concern that sand mining — legal and illegal — on the Cape Flats is removing too much sand from the natural cycle, adding to the beach shortage.
Sand is the main ingredient for making cement.
Hout Bay Ratepayers Association chairman Len Swimmer said the council was partly to blame for the situation by “approving bad developments”.
“The sand has been blocked by development that should never have happened,” Swimmer said. But he welcomed the city’s initiative to address the bottleneck near the beach where sand has almost entirely covered a local law enforcement office.
Concerns about sand are also being addressed by a unique sediment survey conducted by the Council for Geoscience as part of a five-year offshore seismic mapping project.
Marine geophysicist Michael MacHutchon said that by sampling sediment levels offshore, the survey could provide insight into the rate at which sand moved around the peninsula.
“What we ultimately hope to quantify is the rate of sediment transport,” Mac-Hutchon said.
“From this we will be able to calculate the net sediment flux and budgets. If we can show that the rate of transport is slow, we could impose quotas on the sand miners along Macassar. However, at the moment there is just not enough empirical data.’’
The geoscience offshore mapping project would also collect other useful data, such as shipwreck and reef locations.
South Africa is in the process of mapping a vast new offshore area that it hopes to acquire in terms of an international offshore claim.
Bloor said the geoscience sediment survey would help the council to assess and understand “complex” sand dynamics. “This is a very complex issue. We currently monitor our coastal systems, but the geoscience study will be very helpful and guide us into the future,” he said.