Planned dredging of Lower Silvermine Wetlands (LSW) imperative to mitigate flood risk
02 April 2023
Dredging work starts the first week of April on the LSW to reduce the risk of flooding for residents of the surrounding areas. This work is being done as part of ongoing river maintenance and programmes to improve inland water quality.
The area to be dredged is approximately 79 000 square metres, starting from Main Road until the major wooden footbridge that runs between Hilton Road and Carlton Road. The City’s Catchment, Stormwater & River Management (CSRM) branch is investing approximately R7 million into the project.
It is necessary in order to remove silt and litter as well as the expansive reed beds, and create open water for the endangered Western Leopard Toad, as well as bird and fish species.
The dredge will remove the excess silt and sludge from any sewage spills, wildfire erosion and stormwater runoff. This will then reset the water capacity of the ponds back to their original levels.
The current levels of silt in the ponds have resulted in the decreased hydrological capacity necessary to prevent flooding.
What to know about dredging
Dredging is the mechanical removal of accumulated sediments/silt deposits, including invasive water plants, litter and solid waste, using excavators.
Over time, this area has become concentrated with both pollution and alien invasive vegetation. The polluted top layer of sediment is being removed, leaving cleaner sand underneath.
Excavators inside the river remove the sediment and move the dredged material towards the river banks. The material is then lifted by means of a long boom excavator to stockpile it 10 m away from the banks and allow for dewatering for three weeks or more before the material can be carted away to the relevant disposal site.
‘The Lower Silvermine Wetlands has been used as a reference location as to what urban waterways should look like – an interface between the environment, people and wellbeing,’ said the City’s Acting Mayoral Committee Member for Water and Sanitation, Councillor Siseko Mbandezi.
As such it is crucial that this dredging take place. It is expected that phase one is to be completed by 30 June 2023.
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Published by:
City of Cape Town, Media Office
