Completion of Avon River Precinct In-river Works

3 April 2015

Covering a 3.2 kilometre section of the Avon River through the city centre, the in-river works portion of CERA’s Te Papa Ōtākaro/Avon River Precinct (ARP) Anchor Project is now complete.

As part of the Opus-led design consortium for the ARP, EOS Ecology’s Shelley McMurtrie was the Ecology and Design Lead for the in-river works – one of the largest urban waterway revitalisation programmes in New Zealand. City Care Ltd worked closely with the design team and EOS staff to ensure the ecological design principles were realised during the construction phase.

As a historical transport route, a centre for trading and food gathering for Ngāi Tahu, and a key part of Christchurch’s character, Ōtākaro/Avon River is a place of great significance for central Christchurch. “Enhancing the health of the river is at the very heart of the development of Te Papa Ōtākaro/Avon River Precinct. With EOS Ecology’s help, life has started to return to this treasured central city waterway – reinstating the Ōtākaro/Avon River as a prized source of mahinga kai,” said Rob Kerr, Development Director for Christchurch Central Development Unit (CCDU) Anchor Projects.

With almost 10,000 tonnes of silt removed, 15,000m2 of gravel cleaned, the creation of key riffle habitats, and the narrowing of the low flow channel with ‘fresh plain’ build-outs, this project has revitalised the wellbeing of the river between the Antigua boatsheds and just east of Barbadoes St. EOS Ecology Principal Scientist, Shelley McMurtrie, says the in-river work has been a heartening project to work on. “The works are an example of what can be done to restore health to our streams in other parts of the city that have also been affected by many decades of urbanisation and, more recently, by the earthquakes” said Shelley.

The 1.1km of low build-outs (termed ‘fresh plains’) have an especially important role in maintaining river health. By narrowing the low flow channel and therefore increasing the speed of the water, these build-outs help protect the ecologically valuable gravel areas from silting up again. “The native plants on the build-outs will also help to take nutrients out of the water, while the rough boulder edging provides cover for native fish, especially large long-fin eels. Sediment depositional zones will also trap sediment, making it easier in the future to manage the removal of sediment from the river.”

While long-term monitoring is still being undertaken, the early signs are encouraging with an increase in habitat diversity, fish diversity, and trout spawning in key locations along the river in the central city. “A few days after building one of the fresh plains we found a large long-fin eel in residence in one of the specially-created eel boulder holes – so it is nice to see that they approve of the new habitat,” said Shelley.

EOS Ecology has a detailed habitat and biological monitoring programme that they hope will shed more light on which elements of the in-river works have been most successful. The results of this ongoing programme will then be fed back to the global restoration research community.