November 2016
Sustainable Urban Drainage Systems (SuDS) - Part Two

Continuing with the topic on SuDS, I would like to complement my last entry to the blog with a few examples of their use in New Zealand.

Rain gardens in New Zealand - Wellington

In Wellington, there are many examples of rain gardens working together with other systems of water runoff treatment. In the past few years, the city centre has been redesigned keeping in mind the use of these systems to liven up its infrastructure. Places like Waitangi Park, The Quays (Jervois, Customhouse and Waterloo Quays) and Cuba Street have been successfully redesigned.

Waitangi Park

This project is an excellent example of ecological infrastructure carried out by a team of landscape architects and engineers for the Wellington Waterfront Limited. It has received numerous and deserved prizes and, amongst other things, has increased the biodiversity of the waterfront in this city, encouraging renewable energies, conservation and recycling and treatment of water runoff.


Aerial view from Google Earth of Waitangi Park

Waitangi Park has approximately 6 hectares. Before this intervention, the park was an underused space with high potential in a prime location. This project has integrated the park with its environment and has managed to bring people closer and make it their own space.

Its redesign has also been done with great sensitivity towards the historical value of the area from pre-European times. In those times, this was a natural wetland area used by Maori for navigation, food collection and as a water source.


The new concept is characterised by the recuperation of the Waitangi stream which was part of these wetland and that was posteriorly channelized underground in the XIX century. The stream is now diverted to a new bioretention system where the water is collected via a dam and it is then pumped to a wetland area where it is filtrated by rushes and reeds purposely planted for this. The water then passes through a series of terraced zones densely planted where the filtering process continues. Once filtered, the water is then directed towards a pond where it is stored to be reused in the park irrigation. The excess of water is discharged into the harbour after filtration.


A wide pedestrian walk, which incorporates additional infiltration areas such as, for instance, the tree pits, where the runoff from the road is redirected, and the rain gardens with a similar purpose complement the design.


For further information you can visit the following link to the company which led the professional team: WAAL

Rain gardens in Waitangi Park – Wraight+Associates photo
Rain gardens in Waitangi Park – Wraight+Associates photo
Rain gardens and Skate Park in Waitangi Park – Photo from Wellington Civil Trust
Wellington Waterfront– Wraight+Associates photo
Wellington Waterfront– Photo from foldedcranes.wordpress.com
Rain gardens in The Quays and Lower Cuba Street
The Quays

This is one of the main arteries in Wellington with traffic of more than 50,000 vehicles per day. Approximately 80 rain gardens have been installed here in the past few years.


The gardens were installed with the intention of beautifying this area and at the same time improving the runoff quality that was discharged into the harbour. I believe the gardens would have achieved a better impact if they were wider.


Aerial view from Google Earth along Waterloo Quay
Lower Cuba Street

This is another ecological urbanism example. The rain gardens here were part of a street beautification project in this shared area between pedestrians and vehicles.


Initially 36 Betula platyphylla japonica were planted, but these were planted immediately after the ground construction and the ground didn’t have time to settle. This resulted in an irregular surface with voids when the ground settled. In order to repair this, it was necessary to remove the planting and then Alnus glutinosa were planted. It will be interesting to see how these trees stand the passing of time and see whether they present a problem for the urban environment and underground services nearby or whether, on the contrary, they perform well.


Due to Wellington’s climate, which as we know, is one of the windiest cities in the world albeit, in my opinion, one of the most beautiful too, these projects used vegetation adapted to these conditions. Some of the species used were:

• Aciphylla squarrosa
• Apodasmia similis
• Astelia grandis
• Carex comans
• Machaerina sinclarii
• Uncinia uncinata

Photo from Panoramio.com that shows the gardens in Lower Cuba Street.
Rain gardens in New Zealand - Nelson

There are also examples of ecological infrastructure in Nelson that, I think, are interesting despite their smaller scope.

Main Road Stoke

Even though this project was not designed as a retention system, it is a good example of an adequate selection of vegetation in New Zealand context. And even if the planting was not purposely designed, to an extent, the vegetation also contributes with the absorption of water runoff.


Nelson City Council decided to plant this open channel to beautify this main artery of the city. The vegetation has evolved very well with time and livens up this residential area on the outskirts of Nelson giving the pedestrian a breathing space from the constant traffic.

Some of the selected species were:

• Poa cita (Silver tussock)
• Cordyline australis (cabbage trees)
• Phormium cookianum (flax)
• Coprosma propinqua

Main Road Stoke showing the vegetated swale
Main Road Stoke showing the vegetated swale
Marsden Valley

This is an example of a rain garden designed for this new subdivision in Nelson located in Marsden Valley. The vegetation brightens up this new neighbourhood. At the same time it maximizes the traffic calming measures through the incorporation of native planting to the tree pits, which has the visual effect of increasing the perception of street narrowing created by these.


Viastrada’s model of Marsden Valley

The streets of this neighbourhood have been designed taking into account the great amount of runoff that can be produced in extreme meteorological events. At the same time, the design has been focused in creating a beautiful and calm space with good connections for pedestrians and cyclists that is integrated in its environment.


Cross-section from Viastrada
Cross-section from Viastrada

Unfortunately, some of the species selected where incapable of tolerating the drought conditions these systems are exposed to and part of the vegetation has dried up. Simply, replacing these species for others more suitable, would accentuate the “Kiwi effect” of this area. By “Kiwi effect”, I am referring to that special and particular feel created when using our unique native planting in the design.






I hope you have enjoyed reading of about this thrilling topic. The following references are the articles and documents which I have consulted and will provide you more information, if required.

References:

·    floodlist.com

·    Sociedad Americana de la Ciencia de los Suelos: (Spanish)

·    www.agronomy.org/news/media-inquiries/releases/2015/1014/713/

·    www.sustainablehort.com/?p=177

·    www.portlandoregon.gov/bes/article/78489

·    www.aucklandcouncil.govt.nz/.../raingardenconstructionguide.pdf

·    wellington.govt.nz/~/media/services/environment-and-waste/environment/files/wsud-guide.pdf

·    rcaforum.org.nz/sites/public_files/documents/Rain-gardens-case-study.pdf

·    rcaforum.org.nz/sites/public_files/images/RAIN-GARDENS-maintenance-guide.pdf

·    www.wellingtoncivictrust.org/awards

·    wellington.govt.nz/recreation/enjoy-the-outdoors/parks-and-reserves/suburban-and-city-reserves/waitangi-park

·    www.studiopacific.co.nz/projects/2010/harbour-quays/

·    www.waal.co.nz/wsud/waitangi-park/

·    wellington.govt.nz/~/media/your-council/projects/files/goldenmile-lowercuba-info.pdf

·    www.ccc.govt.nz/.../15-1297087-Rain-garden-design-construction-and-maintenance-manual.PDF

·    www.researchgate.net/...Tree_Species_Suitability_to_Bioswales_and_Impact_on_the_Urban_Water_Budget

·    www.montgomerycountymd.gov/DEP/water/rain-garden.html

·    www.hidrologiasostenible.com/y-si-tuvieramos-que-inventar-el-drenaje-urbano/

·    drenajeurbanosostenible.org/.../origen-de-los-sistemas-urbanos-de-drenaje-sostenible/

·    ec.europa.eu/environment/soil/pdf/guidelines/pub/soil_es.pdf

·    www.magrama.gob.es/es/calidad-y-evaluacion-ambiental/.../desarrollo-medio-am-urb/#para3

·    www.thames21.org.uk/sustainable-drainage-systems/

·    www.urbis.nl/en/portfolio-items/vinexlocatie-tolhek-pijnacker-zuid/#iLightbox[gallery1679]/0

·    viastrada.nz/news/2010/urban-design-winner-marsden-park-phase-one

·    Google Earth

·    Panoramio.com

·    Ecological Urbanism Revised Edition 2016, Harvard University Graduate School of Design, Lars Müller Publishers

·    Towards Resilient Water Landscape – Design Research Approaches from Europe and Australia, 2009, Oliver Parodi (ed.)