The responsibility for clearing the litter-and-rubble net traps in Marina da Gama’s waterways is about to shift to the City after resident Mike Ryder resigned from his voluntary caretaker role.
City spokesman Luthando Tyhalibongo said the catchment, stormwater and river management branch was taking steps to ensure the nets would continue to be cleaned.
He said the City thanked Mr Ryder for the dedicated services he had performed.
Four years ago, Mr Ryder raised the alarm about the condition of the waterways and then set about organising the nets to catch the rubble and garbage, including some dead animals, that used to wash down the network of canals, straight into the Marina da Gama waterways, and then out to sea (“Second rubbish net for Marina da Gama waterways,” Echo April 26, 2018).
Mr Ryder has resigned from his volunteer duties for personal reasons, including travel.
He said his self-assumed duties included twice-a-month visits to Wild Wood island and environs, to assess the litter situation, and the employment of two workers with adequate safety gear and equipment, such as wheelbarrow, rakes, prods etc. He would provide transport to the site and instructions on what areas to clear.
From his pocket, he supplied lunches and cool drinks for the men doing the work. He’d then collect the men, allow them to shower and wash the equipment and then pay their wages.
“I’m sure the guys who know the drill now will be happy to carry on,” he said.
Mr Ryder, who has a BSc in polymer chemistry from Leeds University, also sent the City a detailed proposal in September to consider raising the rubble weir, which he said was a simple solution to the terrible water quality issues that had dogged Zandvlei, increasingly, for years.
He said raising the rubble weir by a mere 50cm could provide the desired summer water level in the vlei, create a reduction in sand washed up the canal causing the ongoing siltation problem, allow a continuous exchange of water with the sea throughout the summer season – creating a continuous connection to the sea for the all important migration of fish – and allow the regular rise and falls in the Zandvlei water body, encouraging circulation and reducing the stagnation problem in the Marina channels
“All that has to be done is instead of blocking off the mouth entirely with a 3 metre high sand bar – by the expensive bulldozing of sand – just raise the rubble weir for the summer period by 50cm or so,” he said.
It could be done by placing moveable concrete blocks (e.g. concrete traffic-lane dividers laid on their sides) across the top of the weir.
“It must surely be easier to do this twice a year than bulldoze hundreds of tons of sand back and forth every spring tide,” he said.
“I have given this considerable thought and see no reason it won’t work better, be cheaper and easier to facilitate than the existing method of building and removing a huge sand wall. In addition it removes the flood risk the high sand berm presents in an extreme rain event, the likes of which are happening all too more frequently,” he said.
The City, however, is dubious. Mr Tyhalibongo said the question of managing, altering, raising or lowering the rubble weir at the mouth of the Zandvlei estuary had been considered and debated for some time.
“The tidal flow through the mouth is, however, controlled and managed by the rubble weir (for water depth within the body of the vlei), and the opening and closing of the sand bar at the mouth,” he said.
Mr Tyhalibongo said the maintenance and management of these two features were set out in the City’s maintenance management plans for Zandvlei as well as other management documents.
“The mouth management plan supports the environmental authorisation which provides the legal framework for the City to open and close the mouth. The rubble weir also controls the amount of tidal flow into and out of the estuary, which impacts the salinity within the main water body of the vlei,” he said.
However, he added that the City’s catchment stormwater and river management branch was proposing a review of the Zandvlei outlet canal, and would look at including an alternative method of managing the flow through this structure, as part of that process.
