Silverstone Park

Water and CirculationTanya Larson

Contents

Page 1 Title

Page 3 Table of Content

Page 4 IntroductionPage 6 Project 3Page 7 PhotographsPage 10 Design Driver Page 12 Concept PlanPage 13 Surface CutsPage 14 Rain WaterPage 16 Cross SectionPage 17 Rain GardenPage 18 Previous MaterialsPage 19 FilterPavePage 21 Storm waterPage 22 VegetationPage 23 Plant ConceptPage 24 Suggested PlantsPage 25 PhotographPage 26 References/Works Cited

Introduction

The aim of Project Two was to create a recreational area, a park designed to improve the existing waterways and increase ecological connectivity for Silverstone. It was also intended to retain an area large enough to represent a portion of New Zealand’s iconic heritage, and promote walking, hiking and cycling. The design drivers were the rivers flowing through the site.

Within this park, wide paths have been created to encourage users to enjoy the bush and to find relief from the surround-ing built-up urban that is anticipated over the next 20 years. Amenity areas have been created on flatter areas and gradual slopes of land so access is available to the improved rivers. These amenity areas are intentionally left as open space; small, high-design parks within the big park or just long grass. The point is to promote the benefits of healthy rivers and to make them a feature of them rather than a void where garbage is dumped and weeds allowed to take over, as is happening now.

Orange Square marks our site. Water ways flow north east as lines indicate.

For Project Three, the aim is to return as much rainwater as feasible to the water table. To do this we will create rain gardens and reduce the amount of impervious surfaces produced within the park of Silverstone.

Impervious surfaces have an enormous impact on our waterways. They force rainwater in sheets across the hard surface and into the storm water system (See following study of Storm water). The Auckland Region is notorious for its seasonal and heavy rainfall. This rainfall increases as you go north.

Impervious surfaces can also raise the air temperature. ‘Heat islands’ are created, which can cause an increase in energy use, e.g. air conditioning in surrounding buildings, as well as increasing the water temperature, thereby reducing ‘dissolved oxygen-reducing ecological productivity and interrupting the atmospheric carbon cycle’ (Wikipedia, June 4 2011).

The Auckland Region is in a sub-tropical zone and warm much of the year.

There are, at times, good reason to have impervious surfaces. For example if pervious material were used for a large car park it would infiltrate the contaminants discharged by the cars and very quickly clog the porosity of the impervious material, defeating the purpose.

Impervious surfaces are mostly created for motor vehicles. In our first project we looked at promoting the use of public transport but not visually getting rid of the motor vehicle. It is my hope, and I have toyed with it in this third project, to reduce the visibility of the motor vehicle and in doing so, reducing their use.

Planting a rain garden,Delaware Garden Training March 2011

Rain on impervious surface,

Silverstone Park has four small areas of low-density housing. These will largely be made up of three sto-ried terrace style dwellings. The main objective will be to lessen the impact of these dwellings on their sur-roundings. This will be achieved by avoiding, as much as possible, traditional methods and materials used in other subdivisions.

The purple in this image represents areas designated as residential.

Design Driver

Continuing on from Project Two, water and circulation remain the design drivers. Drawings of water movement have been laid over the landscape and used to find patterns and possible solutions to some of the constraints

within the site.

Description of Concept PlanThis is a very simple plan using repetition to its full advantage, and in doing so, returning as much rainfall to the water table as possible. As simple as it is it still is very different from typical Auckland suburbs.With only vegetation in the front yard and no fencing, the dwellings are exposed to the street. Intention here is to improve visibility for the driver backing out of the driveway.

By narrowing the streets and making them one-way and cyclic allows room for rain gardens on both sides of the street. This repetition (as the eye moves across the layers of vegetation) will visually soften the road for residents and those using the walking track. Sidewalks have been moved to the centre of the street with vegetation on either side providing a more attractive and safer experience when walking the streetIt is expected that residents will create their own track to the walkway from their dwelling.

Porous materials will be used for the street, driveways and walkway (See study of FilterPave). All of the streets will be crowned, directing water into the continuous rain gardens. There will be no kerbs.

Concept PlanPoster only, could not scan A2 colour in time.

The pattern seen in the concept plan represents the movement of water. This pattern is cut into the impervious surface, much like expansion lines in concrete. The cuts, besides contributing to the overall design, are to slow the flow of rainwater, aiding infiltration into the impervious sur-face.

Cut

road surface

Rainwater from the roofs of each dwelling will be directed by slope and guttering to a down pipe channelling the water into a holding tank. Each holding tank is situated in the 500 mm space between dwellings. Slowly this water will filter into the rain garden. These holding tanks will provide irrigation during dry spells. There is the opportunity, if filtration were done, to use the water within these tanks for household use. Because of the height of the dwellings, these tanks could be very deep, narrow and long. However, more research is needed.

Stratco guttering, Stratco n/d

The first story of each dwelling will supply garaging for two vehicles and be de-signed to look as part of the house. There will be room for parking in driveways but not for parking on the street.

Cross Section

6m Rain Garden 1m RG 2m Walkway 1m RG 6m RG

3m Street 3m Street

Rain Gardens will circulate the entire walkway and surround the front yard of each dwelling. In the middle of the street is a third rain garden approximately one metre deep, a representation of the existing rivers. This will be especially beneficial during exceptional rainfall but is expected to be ephemeral.

Rain Garden

House Down Pipe (Perforated underground Ground Level Mulch Steel Boxing Street (FilterPave

House floor level minimum .500 above rain garden flow level,

Filter Fabric

Drainage Layer (at least .200mm)

Ponding Area

“Rain gardens look and function like any other garden except they treat runoff and are specifically designed with a layer of 100 mm of mulch, 600 (minimum) to 1,000 mm of planting soil, and vegetation (grasses and shrubs).” “In clay soils, (as at our site) an under drain should always be incorporated into the design of a rain garden to provide adequate drain-age during wet weather. The under drain must discharge to an approved storm water outlet. To prevent the migration of adjacent soil into the planting soil and the migration of planting soil into the under drain material, filter fabric is required”.

(Waitakere, November 2004)

A look at some Pervious materials

Pervious concrete: “A pervious concrete mixture contains little or no sand, creating a substantial void content. Using suffi-cient paste to coat and bind the aggregate particles together creates a system of highly permeable, interconnected voids that drains quickly.” (Pervious Concrete, 2010) Widely available (in the US) and can bear frequent traffic. Has less flexibility than the following:

Porous asphalt: “Porous asphalt consists of standard bituminous asphalt in which the fines have been screened and reduced, creating void space to make it highly permeable to water.”(Porous Asphalt, n/d) FilterPave: “is a single sized aggregate made from recycled post-consumer glass this is a hard surface, porous pavement.”

The pros for all of these materials are that they infiltrate water on site, preventing it running across the surface, picking up contaminants along its way then flowing into the storm-water systems.

Materials to Use

For this site I am promoting the use of FilterPave.

It is a tough and colourful material made from recycled glass. FilterPave’s production has a low impact on the environment, it would help utilise a product New Zealand is producing much of and it is good for light-to-heavy pedestrian and vehicular traf-fic loads.

Presently New Zealand can only just manage all of its recycled glass requirements, and that is due to recent upgrades to the country’s only glass recycling plant. Considerations are being made “to look into the practicalities of crushing the glass and shipping it to South Australia” (Zero waste, 2011). This suggests the need for further uses in New Zealand.

FilterPave’s Pros:

The following points have been made by the Storm water Academy within the University of Florida ref. Research results, 1996-2011.

It is stronger than porous asphalt and has more flexibility then pervious concrete.

“The glass used in the pavement undergoes a special process that rounds the edges and cuts the particles into specific sizes and shapes. This aggregate glass loses its brittleness and is claimed to be even harder than stone. The final product is strong, safe for use around plants and animals and is 38% porous” (Ecofriend, 2010).

Almost twice as porous as pervious concrete when well maintained. Even with less than minimum maintenance the infiltration rate remains high.

Water quality is increased with a 33% reduction in phosphorous and nitrogen.

Problems: High maintenance, with quarterly vacuuming required. ( Note this applies to other impervious surfaces).

It costs more than other pervious surfaces.

Storm-water

Storm-water has been identified as a leading source of pollution for all water bodies.

As rain falls (or snow melts, in some areas) the water flows in sheets over impervious surfaces, picking up and taking with it all the contaminants on these surfaces. This could include fertilizers, garbage, gas, oil, pathogens, heavy metals, and animal litter. This water runs directly into storm water drains. It flows, gaining force and velocity on its way, straight into our rivers and streams. It is not treated as is commonly thought.

The force at which this water flows can cause erosion and sediment placement. This in turn can cause flooding. But, more importantly, all of the contaminants are now floating through the fresh (and salt) water-ways poisoning them.

By slowing the speed at which the water flows, infiltration can occur, more easily, where the rain falls - vastly decreasing erosion, sediment movement and placement and contamination of our waterways.

The only reason everything and everyone on this planet is able to survive is because of fresh water. Poi-soning the waterways is self-destruction.

VegetationIt is anticipated that the owners of dwellings will wish to add their own personal touch to their front yard. A plant guide will be provided, recommending the types of plants that will benefit their rain garden and help maintain an overall unity in the district.

We will plant each front yard, differently, using the same plant varieties to get the rain gardens functioning and in the hope that owners will appreciate, enjoy and manage their surroundings.

Planting Concept

Baumea articulata Up to 1.800m Prefers boggy areas but can tolerate drier conditions.

Cordyline australis 12 - 20m Tolerates very wet and moderately dry.

Cortaderia fulvida 1.5 – 2.5m Copes with moist or dry conditions.

Cyathea dealbata 2 – 4m Prefers shade and moist conditions.

Eleocharis acuta .5 -.5m Prefers boggy areas and will grow in shallow water.

Leptospernum scoparium 3 – 5m Tolerates most conditions, wet, dry, windy.

Libertia grandiflora .5 - .5m Tolerates boggy through to semi dry soil.

Phormium cookianum 1 – 1m Grows in any reasonable soil.

Phormium tenax 2 - 2m (smaller hybrids available) Tolerant of boggy soil conditions.

Pseudopanax crassiflius 4 – 15m Tolerates any soil conditions.

Pseudopanax laetus 2 – 4m Any reasonable soil.

Rhopalostylis sapida Up to 10m Moist deep soil.

References/Works Cited

Brickell, Christopher (Editor in Chief)The Royal Horticulture Society A-Z Encyclopedia of Garden Plants.Dorling Kindersley Book UK 1996This Edition Covent Garden Books UK 1999

Cave, Yvonne and Paddison, ValdaThe Gardeners Encyclopedia of New Zealand Plants.Godwit/Random House 2003

Makhzoumi, Jala and Pungetti, GloriaEcological Landscape Design and PlanningThe Mediterranean ContextE and FN Spon 1999Imprint of Routledge London and New York

Phillips, ChristineSustainable PlaceWiley-Academy 2003

Salmon, J.T,Native Trees of New ZealandHeinemann Reed, a division of Octopus Publishing Group (NZ). First published 1980, this print 1990

http://www.awbury.org/RainGardens2.htm June 6, 2011

http://www.dauphincd.org/swm/BMPfactsheets/Porous%20Asphalt%20fact%20sheet.pdf (June 12, 2011)

http://www.ecofriend.com/entry/eco-tech-filterpave-recycled-glass-pavement-captures-rainwater/ (June 12, 2011)

http://www.hillsdalecounty.info/planningeduc0004.asp (June 4, 2011)

http://www.landcareresearch.co.nz/research/built/liudd/documents/ARC_Stormwater_raingarden_Plants.pdf (June 9, 2011)

http://www.landcareresearch.co.nz/publications/researchpubs/raingarden_poster_page1.pdf (June 4, 2011) Rain garden layers

http://www.northshorecity.govt.nz/Services/Environment/StormWater/Pages/OverviewOfConsiderationsWhenDevelopingOrBuilding.aspx (June 6, 2011)

http://www.perviouspavement.org/ (June12 2011)

http://www.prestogeo.com/filterpave (June 4, 2011)

http://www.waitakere.govt.nz/cnlser/wtr/pdf/stwtrsol/swsolut-res-sites-sect6.pdf (June 4, 2011)

http://en.wikipedia.org/wiki/Impervious_surface (June 4, 2011)

http://www.zerowaste.co.nz/default,754.sm (June 12, 2011)

Plates

http://www.swc.dnrec.delaware.gov/coastal/DNERR/Pages/CTPRainGardenTraining.aspx (June13 2011)

http://www.google.co.nz/imgres?imgurl=http://desktop.freewallpaper4.me/view/original (June13 2011)

http://www.stratco.co.nz/nz/products/gutters.asp (June 9, 2011)