Cape Town - A much-anticipated dredging project is due to begin on Saturday at the overstimulated Lower Silvermine Wetlands (LSW), between Clovelly and Fish Hoek, which has become heavily infested with reeds and suffers from frequent flooding, biodiversity loss, and even safety issues.
Run-off from a golf course upstream, minor sewage spills, and natural siltation have resulted in a massive influx of nutrients into the water of the wetland which has exacerbated siltation and encouraged reed growth. This has closed-off open water ponds and channels within the LSW, which is managed by the City.
Councillor Alex Lansdowne, deputy chairperson of the mayoral advisory committee on water quality in wetlands and waterways, said: “The dredging of LSW will have immense benefits for biodiversity.
“The endangered western leopard toad occurs here and the opening of the ponds and channels will create more breeding habitat for this threatened species. The clearing of the reed overgrowth will also increase line of sight which will improve security and usability for the local community and user groups.”
Acting water and sanitation Mayco member Siseko Mbandezi said about R7 million was invested into the dredging of the upper wetland with phase 1 to start on April 1, and was expected to be completed by June 30.
Lansdowne and Mbandezi said the anticipated dredging was of critical ecological importance because it was the breeding habitat of the endangered western leopard toad, it suffered from reduced plant diversity and displacement of locally indigenous plants with reed beds, and increased flood risk to residential properties.
Mbandezi said: “Other waterways within the City are being modelled after LSW – as a reference location for what urban waterways should look like – so the wetlands must be maintained properly to continue this function.”
Lansdowne visited Fish Hoek with City officials, water quality advisory committee members, and local community stakeholders on Tuesday as part of their preparation to dredge the LSW.
At the meeting, officials were interrupted by screams from a nanny who was being mugged in the high reeds. The woman, who did not want to be named, was pushing a toddler in a stroller along a frequently used pathway when she was accosted by a man who tried to snatch her phone. When City officials ran towards them, the man took flight.
Dave Balfour, chairperson of Friends of Silvermine Nature Area (Fosna) - a group of local community members concerned about the catchment - welcomed this dredging work and explained as it sits in the lower reaches of the Silvermine River, the wetlands were vulnerable to regular discharges of raw sewage overflow when the Vallyland sewage pump station either experiences a breakdown or when there is load shedding and the build-up of sewage is discharged into the wetlands.
“The dredging will aim to create large bodies of open and deeper water which will better serve and attract different wildlife including water fowl and local otters as well as habitat for other aquatic diversity. A central island, which we hope will be created, will serve as a refuge for some sensitive species,” Balfour said.
At the meeting, officials were interrupted by screams from a nanny who was being mugged amid the high reeds. The nanny, who did not want to be named, was taking a stroll along a frequently used pathway while pushing a toddler in a stroller when she was accosted by a man that attempted to snatch her phone.
When City officials came running towards them, the man took off and abandoned the mugging.
Fortunately neither the nanny or the toddler were harmed. Balfour added that there were occasional incidents of this nature as a lot of local citizens walk that pathway recreationally, as well as those who use it as a transit route.
Local resident and Fosna member Kim Kruyshaar added this was a proclaimed biodiversity area, and they were losing the biodiversity - that was the main issue and why these ponds needed to be dredged.
“We have pleading and begging for this dredging for so many years because we've lost the open water bodies, we've now got this rampant reed growth going into the dryland areas and outcompeting the plants, it is also very high which affects visibility and makes it a safety issue as well,” Kruyshaar said.
Kruyshaar said that school groups often came to the wetland to observe otters, over 50 bird species, water mongoose and sometimes even buck that come down the mountain to the wetland.
kristin.engel@inl.co.za