Streams see the light of day
By Meg Liptrot | NZ Herald
Last Saturday saw the opening of a stream daylighting project at the La Rosa Garden Reserve in Green Bay. It was a brilliant blue-sky day and the community came out in force to celebrate. Many who attended live nearby and were clearly thrilled to witness the rebirth of two streams in their reserve. The previously underground, piped streams have been 'de-culverted' and opened up to the light of day. It is clear to see in the well-designed plantings and walkways that the community will get a lot from this project, particularly those weary souls wishing to reconnect with nature after a long day in the office.
Nearby schools and early childhood centres are already anticipating learning opportunities from the park, and have been involved in water monitoring, planting, and creating permanent and ephemeral artworks. The La Rosa concept plan was developed by environmental consultancy, Boffa Miskell in 2012. The design thinking which went in to the project is one of community inclusion. Pa Harakeke plantings include varieties of flax for customary use, and a community orchard has been planted by locals. The band of enthused food growers have already been offered a spot to locate rainbarrels by a friendly neighbour so they can water the new orchard, and have plans for monthly get togethers.
This is one exciting project that could be repeated throughout the country. How crazy is it that our beautiful cities have some of the most scenic assets buried underground? Walk up Queen Street and you're walking up part of an historic stream. Myers Park also has a stream piped underground. In the past we've buried and piped traditional food gathering areas, wildlife habitat, and migration pathways for eels and native fish under asphalt or grass throughout outlying suburbs in the majority of our cities.
I chatted with Auckland Council environmental scientists Martin Neale and Peter Hancock who were stationed beside the new boardwalk inviting passers by to check out the intriguing creatures popping up already in the reborn streams. Martin and his team are contracted to monitor the streams before and after the daylighting process. I was surprised to discover that we are still intent on damaging waterways and the 2010 State of the Auckland Region report declares that between 2000-2008 around 80km of streams were subject to a resource consent for stream disturbance. This may include piping, lining, channelling or damming waterways and all have various adverse effects on water quality, ecology and flood management. Not to mention the fact that once a stream is altered, it is an almost impossible exercise to get it back to it's original state.
Tom Mansell, stormwater engineer and overall manager of the project believes the two streams Parahiku and Wai Tahurangi (Avondale) were piped in the reserve in the 1970s to make life easier for the park's maintenance contractors so they could easily mow both sides.
The earthworks and construction for the project began in February this year as one of the Mayor's top 100 projects to make Auckland 'the world's most liveable city'. It is Auckland's first dedicated stream-daylighting project. Despite the process being an expensive exercise, there are long term cost benefits of having a natural stream versus culverts which need upgrading and maintenance. Although there's little chance of Queen St being daylighted, a number of Auckland local boards are putting their hands up for stream daylighting or similar projects in their areas, and a couple are already in the 'pipeline', so to speak.
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 a '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.
Four generations of the La Rosa family attended the celebration and blessing by local iwi of the reserve. I chatted with Phyllis La Rosa, now 90, and her son Charles who recalled the streams before they were culverted underground. The reserve was once part of their dairy farm of around 90 acres. Charles could remember freshwater cray (koura) in the streams when he was young. It was touching to see Mrs La Rosa walk along the new board walk with her son, admiring the streams, knowing future generations of her family and the community will get to enjoy this reserve, safe from future development.