In December 2010, the Mayor’s office chose the twin stormwater culvert tributaries located in the La Rosa Reserve in Green Bay, West Auckland, to be the councils “flagship” stream day-lighting project. The award winning La Rosa stream showcased EDC’s bio-engineering techniques for stream restoration and fully illustrated how a community can be reconnected with their local stream.

Stream day-lighting is the practice of bringing buried pipes to the surface and restoring natural streams in their place. Naturalised streams offer multiple benefits over pipes, including restored habitats, enhanced stormwater management, and a natural asset for the community to enjoy. These streams play an important role in enhancing the natural environment, but more importantly are vital in managing stormwater overflow. However, many of Auckland’s streams have been directed through lifeless concrete pipes, harming their ecosystem and reducing their capacity to manage high levels of rain water.

Natural features such as rocks, stones and tree branches were added to replicate the streams’ condition prior to them being piped, and new walkways and public artworks in the reserve has created a place where the community can connect with the natural environment. Returning streams to a more natural form supports a greater level of biodiversity in and around the stream, and protects the stream banks from erosion.

The daylighting process at La Rosa Reserve involved the removal of 5000 cubic metres of clay fill and 180m of culvert pipe. The stream gullies were shaped then lined with geotextile and quarried stone to prevent erosion. The slab-like boulders were chosen for their angular shape to ensure they couldn't roll downstream during periods of high rainfall. Although the streams were originally 'muddy-bottomed', daylighted streams require stone landscaping to mimic natural stream hydrology. This prevents water scouring out the clay which would cause sedimentation issues downstream.

Thoughtful details included the subtle elevation of boulders near the new bridges for the ambient sound of falling water. Logs, taken from the few trees removed during construction were placed along the banks to create more habitat and provide food for macro and micro invertebrates; which will ultimately become fish and eel food, helping restore the natural lifecycle of the streams.

The lessons learnt from this project will prove useful for the ongoing delivery of other stream daylighting projects in Auckland, something that is likely, following the positive response to the La Rosa project since completion and opening to the public