Published on 04 September 2023
Keen eyed observers of the Oamaru Harbour will have noticed some heavy plant machinery at work on the breakwater over the last week. Around 2000 tonne of rock has been placed on the sea-ward side, as part of maintaining the revetment and protecting the breakwater. A revetment is a sloping structure designed to absorb and dissipate the energy of waves in order to reduce coastal erosion.
The rock was supplied and placed by Road Metals, using a 30 tonne excavator and 35 tonne loader. 75% of the rock placed ranged between 7 and 26 tonne in weight. Contractors also removed unsightly concrete on the McAndrew wharf which runs parallel to the breakwater.
The cost of this necessary coastal erosion prevention was $130,000.
Rock revetment work took place opposite the harbour wall near the sheds opposite Sumpter Wharf in 2022, and the breakwater itself was last added to in 2021.
Grant Rhodes, Property Manager for Waitaki District Council, said: “Regular rock revetment is important for the physical wellbeing of the Harbour, and with the winter weather now easing it is important for us to check the breakwater and add to the existing rocks where necessary”
Later this year Council will be conducting a Lidar survey to monitor rock loss on the revetment walls that protect the Oamaru Harbour. LiDAR surveying uses laser pulses that calculates distances and captures precises measurements. While this is a sophisticated monitoring tool, it is also a quick, simple, and accurate way to collect data.