Runde River – Zimbabwe
- Purpose: to desilt the river weir for pump abstraction
- Performance requirements: Non electro-mechanical operation; Automatic on to pass flood in river; Close to retain FSL
- Type: TOPS gate
- Size: 12 m long by 4 m high
- № off: 1
- Manual override: yes
- Material: Mild steel wit polyamine coating
Location: Runde River, Zimbabwe
Client: Murowa Diamonds (Pty) Ltd
Consultant: Hart Frost Consulting
Contractor: De Sousa, Harare
Scope of services: Design, Project Management, Installation, Commissioning
Murowa Diamonds (Pty) Ltd required a safe pump extraction from the Runde River, one which would be relatively free of sediment in order to give adequate emergency storage in the weir as well as a reasonable life span.
In order to effectively keep the weir relatively free from sediment, the scour waterway should be large, capable of taking the 1:2 year peak flood.
Because it is a remote site, an electro-mechanically operated gate could not be considered. The scour gate had to be fully automatic to open and close to pass floods. The consultant selected the FDS Automatic Scour gate to meet these requirements.
A 12 m long TOPS gate was installed to retain 4 depth of water. The gate is activated by a siphon discharge from the ballast tank to open the gate fully when the water level rises. 0,5 m of water flows over the gate before the gate opens.
The gate stays open while the water level is drawn down by about 1m in the weir and then closes. This allows the sediment laden water to pass through the weir whilst still in motion, and then the weir fills up with relatively clear water afterwards.
The gate is lined with a concrete skin to the upstream and top sides of the gate to prevent damage to the gate from hard floating objects.
This gate works frequently, whenever there is a large flow in the river, to open and close automatically.