Located in one of Auckland’s deepest flood plains, the wetland is designed to hold floodwater volumes of up to 58,900m³ – the equivalent capacity of 23.5 Olympic size swimming pools.
The wetland is designed in the shape of a tuna (eel), a culturally significant motif that provides the stormwater management system with a mechanism to reduce the speed of water entering the catchment area through a network of high volume intake pipes at up to 16m³ of water per second.
Dam design experts on the project worked with Ted Ngataki and Maaka Potini, local Maori artists, to incorporate Tikanga Maori and the concept of a tuna/ eel into the Wetland design.
The tuna was selected as having particular significance to iwi as they are indigenous to the area and were once prevalent and a key part of traditional diet and trade.
Boffa Miskell associate partner and landscape architect Mark Lewis says that the project team worked closely with Auckland Council and mana whenua to develop diverse native planting types, representing historical vegetation in the area.
“One of the key outcomes of our consultations with local iwi and hapū will see the establishment of hectares of harakeke and purei wetlands, and large stands of kahikatea, kanuka, podocarp, and broadleaf forest types,' says Lewis.
“These restored natural systems will connect mature vegetation remnants scattered across the site.”
Peter Norfolk, project manager from Tonkin Taylor, says the new wetland is uniquely designed to act as a dam in both directions – holding the wetland water in during normal operation but overtopping into the wetland in very large flood events to provide additional flood capacity in the floodplain.
“The tuna design was chosen for both its cultural significance to mana whenua as well as for functional purposes.
“The complexity of the S-shaped design with its winding curves and varying elevations is necessary to control the high velocity of the water entering the forebays through 2-2.5m pipes – reducing it to a slow, meandering stream and filtering the water to allow the natural removal of sediment and pollutants before it passes through a green outfall into the Hingaia Stream and into the Manukau Harbour,” he says.