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Cotton Tree Water Sensitive Urban Design (WSUD) Demonstration Precinct

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Sunshine Coast Regional Council

OVERVIEW      

The intent of the project is to promote and educate the development industry and general public in the practical application of Water Sensitive Urban Design principles through the experimental use and trialling of new products and construction techniques.  Ultimately, this encourages responsible water management and leads to the improvement of the health of the local waterways.

Special Factors:    

The unique characteristics of this project are the various WSUD treatments trialled including:

  • Five varieties of swale treatments

  • Rain water harvesting

  • Five types of porous pavements

  • Use of a variety of recycled products

Total Budget:       $600,000

Innovative Design or Demonstration of New Direction

Since the early 1990’s, Water Sensitive Urban Design (WSUD) has been suggested as a key principle in moving towards more ecologically sustainable land development practices and improved water quality outcomes. However, a lack of local applications exists to assist in this development.

This demonstration project’s intent is to educate the public, industry and government on practical applications of WSUD principles through experimentation and trial of new products and construction techniques.

The innovation and new direction has been achieved by:

  • Show casing of many differing WSUD treatment options and techniques, both structural and non-structural within Maroochy Shire Council and in one precinct for accessibility

  • Demonstrating that WSUD can be incorporated into new and the existing urban fabric without compromising functionality and aesthetics

  • Promotion and education of WSUD outcomes to developers, consultants, Council staff and the community in what a WSUD landscape may look like when retrofitted within the existing urban fabric (though equally applicable to the Greenfield context)

  • Continual development throughout the design process in seeking better opportunities to integrate WSUD principles

  • Producing a landscape that would serve as a reference location for those involved in urban design and asset management wishing to observe real life applications of WSUD

  • Post construction evaluation of project to assess costs and benefit of the various treatments utilised within the precinct and guide future use

Design Concept:

Our major river system, the Maroochy River, continues to show signs of decline in ecosystem health, with increased urban runoff a contributing factor.  Unlike many projects, which fail to realise the master plan vision, this project has delivered on the vision to establish a WSUD demonstration precinct at Cotton Tree and take a leading role in integrated water management within an urban landscape.

The following is a list of the delivered WSUD outcomes:

  • Rain water harvesting

  • Rain water tanks

  • Flow attenuation

  • Rain garden

  • Infiltration swales

  • Porous pavements

  • Pollutant removal

  • Bio-retention swales

The concept was further strengthened during the design development process through the following decisions:

To increase the variety of swale treatments: 

  • Rock infiltration,

  • Vegetated bio-retention,

  • Vegetated infiltration,

  • Grass,

  • Pebble mulch bio-retention 

To increase the range of porous paving to 5 types

  • Boral Hydrapave

  • Hanson Eco Monarch pavers

  • Hanson Grass pavers

  • Permapave Permeable pavers

  • Atlantis Drainage Cells

To use recycled materials

  • Recycled plastic bollards

  • Tip mulch (recycled green waste)

  • Atlantis drainage cells - recycled polypropylene

  • Specifically used boulders/gravel that are used for road construction to minimise demand for landscaping products sourced from non-sustainable sources e.g.: Mary River gravel

Appropriateness to Function:

The site exists within a medium density mixed housing precinct with community facilities and sporting activities adjacent.  Previously it was an informal gravel car park for approximately 100 cars with poor access through the site connecting community facilities through undefined footpaths.  Vast improvements to this landscape have been achieved while still fulfilling the area’s primary role as a car park.

Car Park

  • The car parking numbers have been retained and formalised into a WSUD designed layout that serves the following community uses for both local residents and tourists:

  • Cotton Tree Library

  • Tennis Courts

  • Bowls Club

  • Child care facility

  • Football pitches

  • CWA

  • The function of the car park has now been retrofitted as a demonstration WSUD site for users to be either become informed or not -  by demonstrating that WSUD can be seamlessly retrofitted within the existing urban fabric

Storm water management

  • Previously the stormwater would travel across the site from various sources, into the trunk drainage system and directly to the river, with its associated high sediment and nutrient load 

  • Now it is managed on-site and disconnected from this process through stormwater harvesting and treatment

Playground facilities

  • The existing facilities have been upgraded to improve safety, with fencing and replenishing depleted softfall material

Pedestrian access

  • The footpath network has been rationalised in a formalised structure, providing safe access through the site to the local community facilities

Response to Brief:

The key outcomes for the project are to achieve the Maroochy River Recovery initiatives of improving the water quality of the Maroochy River and promoting the practical application of Water Sensitive Urban Design on the Sunshine Coast. 

Sunshine Coast Regional Council sought to establish a precinct to demonstrate WSUD principles in an existing urban area that complemented the form and function of the existing built environment and contributed to improving the health of the local waterway. It was intended that the precinct would serve as a reference location for those involved in urban design and asset management wishing to observe real life applications of WSUD.

The site characteristics and project outcomes had to include:

  • High visual impact;

  • Close proximity to the Maroochy River and within its catchment

  • Involvement of a council building;

  • High environmental priority;

  • Litter hot spot;

  • Treatment train within walking distance;

  • Accessibility to the general public;

  • Variety of WSUD measures able to be applied;

  • Pollutant removal effectiveness;

  • Improved discharge to river or creek;

  • Able to be finished on time;

  • Able to be finished on budget; and

  • Near existing urban centre

The final landscape reflects the above targets and the key outcomes of education and improved waterway health by a near total disconnection of the site from the trunk stormwater.  Value adding by increased response to the brief through even further experimentation and showcasing of a greater variety of WSUD products and solutions was also achieved

Social, Cultural, Historical, Physical & Natural Context:

Social & Cultural

  • The site is located in a mixed use residential district within easy walking distance to Maroochydore CBD. It was important to ensure that the practical application on site achieved its target of providing education for the community in WSUD techniques. This was achieved through:

  • Information days for local environmental, planning and design professionals

  • Fact sheets for the development industry, consultants, councillors and other community stakeholders

  • Up skilling in WSUD design and construction techniques within Council’s civil and landscape construction staff

  • Location of the site within a high use recreation, residential, tourism and commercial precinct

Historical

  • The original concept design produced by external consultants concentrated on the direct interpretation of the brief.  However, during the design development phase, coordinated by the Council’s Landscape Design Unit, a significant 80 year old Melaleuca quinquenervia, previously ear marked for removal was retained, preserving some of the historical and ecological context of the existing site

Physical and Natural

  • The Maroochy River Recovery initiatives have been achieved through the removal of pollutants by secondary and tertiary water treatment measures e.g. bio-retention swales/trenches, ground infiltration and processing of nutrients through plant uptake/biological processes


Quality of Implementation of Built Work:

Council’s commitment for the project was approximately $600,000 of which $134,000 was directly attributed to WSUD elements with a further offset against traditional materials and techniques if conventional design and construction had been adopted.  The construction began in mid 2006 and was completed in various stages by November 2006.

Project Management

  • Through the use of internal Council design and construction teams, and a commitment by Council to a coordinated project management approach of ‘cradle to grave’, the planning and design intent was not compromised during the construction process

Materials

  • Given the diverse range of pavement finishes and swale construction techniques adopted within a relatively small area, additional construction time and costs were required to construct high quality landscape finishes beyond what is normally delivered for a civil construction project

  • Some of the findings from the post project evaluation identified that the Atlantis drainage cells were the easiest and cheapest to install, although the Permapave treatment appears to have been the most successful product whilst also being the most expensive

  • Soft Landscape works were installed to the best practice industry standards

  • Species selection included sourcing plant material from the nursery door as part of Council’s rigorous Quality Assurance process

  • Preparation of the topsoil included the use of ‘Terracottem’ soil conditioner and wetting agent in order to minimise water use during the establishment of the plants

Asset Management

  • Sunshine Coast Regional Council’s designers and asset managers will monitor the site for the long term performance and maintenance implications of each pavement product. Local industry developers and designers can also utilise the site to “shop” for different styles and combinations of porous pavement and bio-filters to suite their individual needs

Sustainable Policies or Practices:

In recognition of the importance of water to our environment, Sunshine Coast Regional Council has embarked on a suite of projects aimed at demonstrating, promoting and encouraging responsible water management within our region. These projects are identified as part of the Maroochy River Recovery program. The Cotton Tree WSUD Demonstration Precinct was one of the projects

The key environmental elements for this project include:

Rain Water Tanks

  • Three types of tanks were connected to existing downpipes of Maroochydore Library as both a demonstration of differing tank styles and as alternative water supply to public toilets

  • The tanks installed at the front of the library connect to the cisterns of the public amenities and within the administration building toilets

Rain Garden

  • While providing important landscape amenity, the rain garden performs a bio-retention and infiltration function.  Overflow from the rainwater tanks in front of the library connect into the garden, which also receives surface flow from the surrounding paved surfaces and covered walkway roof. The basin has been sized to accommodate an event of at least a 1 in 2 year magnitude (10 minute duration) before being directed into the existing drainage line in extreme events

Flow attenuation and pollutant removal at Beach Parade Car Park

  • Porous pavements, infiltration swales and bio-retention swales have been incorporated into the new car park infrastructure to aid flow attenuation and pollutant removal

Recycled materials and products

  • An emphasis on the use of sustainable landscape materials throughout the design process has resulted in the development of a ‘low resource intensive’ landscape with resources drawn from renewable sources including:

  • Recycled plastic bollards

  • Recycled hardwood timber bollards

  • Tip mulch (recycled green waste)

  • Atlantis drainage cells - recycled polypropylene

  • Boulders and gravel aggregates sourced from sustainable sources

  • Research into other options for the use of recycled materials such as recycled aggregates including roof tiles and concrete was also investigated

Biodiversity and Local Ecosystems:

Urban run off is a major pollutant of the Maroochy River, with increased sediment loads and stormwater surges causing stream and habitat destruction.  The Cotton Tree WSUD Demonstration Precinct supports local ecosystems by improving stormwater quality at the source and the dissipation of water which previously flowed directly into the Maroochy River

Storm water improvement initiatives utilised in the  WSUD demonstration precinct reduce the impacts on surrounding ecosystems and the health of the maroochy river through:

Water quality improvement

  • Removing sediment through infiltration in porous pavements and swales

  • Removing nutrients through processes of bio-retention

  • Reducing peak run-off flows and facilitating a return to previous run-off characteristics

Education and Demonstration

  • Providing a case study and information to educate public, industry and government on Water Sensitive Urban Design principles, the benefits of water conservation and preservation of creeks and rivers

  • Showcasing sustainable development practices

While WSUD practices have only been implemented in one small part of the catchment the cotton tree project has served to promote the health of local ecosystems by putting a focus on alternative methods of development through education and interpretation

Environment Principles:

The Cotton Tree WSUD demonstration precinct serves as a pilot project within the region that showcases sustainable landscape development practices by addressing urban stormwater management.

The cotton tree project addresses the following environmental outcomes:

Urban stormwater management

  • WSUD outcomes are the underlying driver of this project with many environmentally sensitive treatments to stormwater being implemented such as:

  • Permeable paving – different types

  • The use of detention basins to manage flows in minor rainfall events

  • Highlighting responsibility of developers in collecting, storing and treating urban stormwater

  • Ensures that stormwater network is multi-functional – isn’t only geared for functional civil requirements – promotes natural processes, improves natural amenity and recreation capacity of space

Urban waterways conservation and management

  • This project aids the preservation and improvement of the health of the Maroochy River and is part of a greater Council initiative, Maroochy River Recovery

  • Environmental Health

Conservation of significant historic landscapes

  • Changes from the original concept plan during design development allowed for the retention of a historic 80 year old Melalueca quinquenervia

Public open space

  • The design ensures access to surrounding sporting facilities and complements surrounding pockets of existing open space, including the adjacent children’s playground

Raw materials

  • Selection of materials was influenced by the need to limit environmental impacts

  • Recycled plastic bollards

  • Tip mulch (recycled green waste)

  • Atlantis drainage cells manufactured from recycled plastic

  • Installed boulders/gravel typically used for roadway construction to minimise demand of specialist landscaping products that are of a limited supply
RELEVANCE TO THE PROFESSION OF LANDSCAPE ARCHITECTURE, THE PUBLIC AND THE EDUCATION OF FUTURE PRACTITIONERS:

Expands the Scope of the Profession:

Within the Sunshine Coast region there are few examples of WSUD being successfully incorporated into the development of high use urban environments. The Cotton Tree demonstration project seeks to experiment with these technologies and serves to highlight WSUD construction techniques to the development industry. It has provided a useful case study when evaluating the viability of adopting water quality improvement practices.

The demonstration precinct expands the scope of the profession by facilitating:

Experimentation

  • Innovative site planning and design is demonstrated through experimentation with various WSUD products, construction techniques and testing of their success within a highly urban context

  • The ongoing post project evaluation process has provided the opportunity to assess the economic viability against efficiency and longevity of the products tested

  • The site utilises five different proprietary pavement products and five different swale/ bio-filtration styles

Education

  • Cotton Tree WSUD Demonstration Precinct has been used extensively as a demonstration project and case study during training workshops for Sunshine Coast design and development industry professionals

  • Porous pavement car parks and differing swales were built using Road Management Services Branch’s civil construction team who received education in using new stormwater management construction techniques not previously used.  Whilst the Parks Bushland Services landscape construction team implemented the soft landscaping including the xeriscape garden, rainwater garden and other planted swales

Culture of Change – Storm Water Quality Improvement and Water Efficiency

  • This project has been instrumental in creating a culture of change in the delivery of urban infrastructure projects and their relationship to stormwater quality. The Cotton Tree demonstration precinct is locally utilised as a case study to guide developers and designers during the development approval process to respond to Council’s requirement of effective stormwater management

  • It challenges traditional approaches to car park design, construction and water quality outcomes

Demonstrates the Fusion of Practice and Theory:

While there have been recent developments in the field of WSUD, the significance of this project is through the practical application of these principles to improve water quality within an urban context. The Cotton Tree WSUD initiative provides the opportunity to assess the success and failures of their application.

The Cotton Tree WSUD demonstration Precinct puts into practice cutting edge principles of water quality and management through:

Product Trials

  • The trial of innovative products and ongoing monitoring of the site to assess long term performance and maintenance implications

Demonstrate Contemporary Construction Techniques

  • Challenges traditional approaches and offers alternatives to conventional site planning, design and construction techniques

  • Council is a leading agent in the promotion of WSUD within the region. Policy documentation within the council’s planning scheme and design guidelines specify water source substitution initiatives for all new developments. This project has been successful in surpassing these policy objectives

Analyse Costs and Benefits

  • Provides a practical example that enables the costs associated with integrating WSUD outcomes into infrastructure projects to be analysed

Water Quality Improvement Meets Best Practice Industry Standards

  • Demonstrates responsible water management practices and technologies to reduce pollutants reaching receiving waters

The role and influence of the Landscape Architect:

From the projects inception as part of the Maroochy River Recovery Program in early 2005, to the delivery and post project evaluation phases, Council’s Landscape Architects have had a lead role to establish the vision and coordinate a diverse range of specialist consultants. The involvement of the Landscape Architect throughout every stage of the project has enhanced the design outcomes and ensured the true potential for the project has been realised.

Design outcomes have been enhanced by:

Integration of WSUD practices into the project including:

  • Bio-swales & swales

  • Detention systems

  • Stormwater harvesting

  • The use of permeable paved surfaces

Reduced Resource Use

  • Careful consideration by the landscape architect has influenced the outcome of a ‘low resource intensive’ landscape with minimal use of materials from non-renewable sources including:

  • Use of recycled plastic and recycled HW timber bollards

  • Green waste

  • Research into the use of materials such as  recycled aggregates such as roof tiles and concrete

  • Sourced quarried stones in preference to the use of materials from unsustainable sources such as Mary River Gravel

  • Plant selection and placement saw appropriate local plant species used and the grouping plants according to their water needs

Education

  • The landscape architect coordinated the design development phase of the project, overseeing and educating SCRC in-house Civil Designers in best practice WSUD

  • The project landscape architects have been responsible for initiating information days for local environmental, planning and design professionals to highlight the outcomes of the Cotton Tree WSUD Demonstration Precinct

Research and Investigation

  • Rigorous research and investigation into construction techniques and products was performed by the Landscape Architect. This has resulted in the delivery of design outcomes that challenge the use of conventional treatments and materials

 

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