News | 28 April 2022
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New eco tiles another way to encourage nature

If you are walking or riding along the coast at Cobham Drive, you may spot the special concrete tiles visible at low tide which are in place to encourage native marine life to the strong new rock embankment.

A worker in a hardhat and high-vis vest carrying a concrete tile with a woven pattern on it over rocks on a waterfront setting.

The 40 tiles provide rougher surfaces, edges, crevices and water-retaining holes similar to those that occur on natural rocky shores. They’re designed to increase biodiversity between the low and high tide zone.

We partnered with others who care about the environment on this, and the scientists say the changes should make it easier for things like periwinkles, barnacles, limpets, and different types of seaweed and encrusting algae to establish.

It’s one of many things we’re doing to protect and encourage wildlife, make the reclaimed land here more resilient for the future, and create an appealing place for people.   

With its coastal native plants, seats, decks, walking and bike paths, viewing platforms and wind sculptures, it’s a little strange to think that for much of last century, the defining feature at this end of the harbour was a big brick coal-fired power station.

Two men wearing hardhats and high-vis vests holding a large concrete tile over rocks on next to the waterfront on Wellington's Cobham Drive.

Taranaki Whānui descendant Holden Hohaia says it is fantastic that as Tahitai – the walking and biking connection from the east – was developed, it was also possible to remove old demolition materials from the seabed and foreshore (more than 400 truckloads) and find ways to protect and encourage sea life.

“Kete, traditionally woven from harakeke, can be used to gather kai moana. It’s hoped in time the woven structure and cavities in these tiles will perform a similar function, and effectively become little baskets of sea life.”

Ecological tiles have been successfully used on seawalls in Sydney and Singapore in recent years, and trialled in Auckland as part of the World Harbour Bivalve Restoration Project. However, this is thought to be one of the first times they have been tried on a larger scale in New Zealand as part of a permanent project.

It’s also providing an opportunity to see how they work in an area which sometimes experiences strong wave action.

Department of Conservation experts expect the rock embankment to provide safe nesting spots for kororā. So, making sure little blue penguins can safely come and go between the sea and nests was something designers factored in.

A large concrete tile with a woven pattern printed into it, placed among rocks, with the ocean washing over it.

The tiles were designed by Isthmus to ecological and engineering specifications from Tonkin and Taylor and made locally by Hutt Concrete Products.

Tonkin and Taylor ecologist Susan Jackson says holes, crevices and indentations will also be drilled into the rock in some places.

“The tiles, and the drilled crevices and holes, are two different ways to improve habitat for native species that can struggle to attach to quarried rock or smooth, flat surfaces commonly seen on seawalls.”

Greater Wellington Regional Council and Victoria University of Wellington will be monitoring both types of changes and seeing how they compare to other parts of the embankment. 

Greater Wellington coastal scientist Dr Megan Melidonis says if the techniques prove successful and cost effective, similar ecological enhancements are likely to be recommended or required more often as part of consents for coastal protection structures around the region.

The 430m-long rock embankment is along the stretch between the Troy Street and Calabar Road roundabouts. It’s engineered to absorb and spread the force of waves in strong northerlies, helping protect the most exposed part of this part of the coast and transport route from high seas and storm-related wave surges that are becoming more common with climate change.

Two men wearing hardhats and high-vis vests placing a large concrete tile over rocks next to the ocean.

Deputy Mayor and Motukairangi Eastern Ward Councillor Sarah Free says the project is helping to build a resilient city fit for the future and protecting and growing our biodiversity. 

“Wellington is one of few cities in the world where native biodiversity on land is increasing, and it is great to see those efforts extend into the marine environment.

“This part of the Evans Bay foreshore has gone from being a rubbish-strewn area where I and other volunteers did monthly beach clean-ups, to a much more attractive environment for both people and nature.

“Both the Mayor and I see the work on Cobham Drive contributing to our kaupapa (values) of environmental restoration, and mahi that will also lead us to become a carbon neutral city by 2050.”