Local Government Magazine
3 Waters

Biophilic design Dunsborough, Western Australia

Calibre’s Brendan Oversby detailed a project in Dunsborough, Western Australia, using biophilic design to integrate water-sensitive design with land development. He was speaking at the recent 2018 NZ Stormwater Conference in Queenstown.

Stormwater runoff is an inescapable fact of urban life. For centuries, the drains and pipes that have channelled it away from homes and infrastructure have often been hidden away below ground or, if visible, unsightly and potentially unhygienic.

But a growing demand from the community for environmentally-sustainable development, supported by forward-thinking professionals, has seen water sensitive urban design emerge from the dark – quite literally – as a new urban hero.

Good management of stormwater offers not only flood protection and effective conveyance of stormwater but also the opportunity for water quality improvement.

By combining this with biophilic design, a range of other benefits can also be realised, with outcomes for the community, the environment and the local economy.

The concept of biophilic design is focused around the incorporation of specific elements of nature within the urban form. These include clean water and healthy vegetation.

So, designing and implementing water management structures that incorporate local vegetation, provides connection for the community to these elements of nature.

Auckland Council’s Guideline Document for Water Sensitive Design (WSD) of Stormwater (GD04) recognises the significant crossover between WSD and urban design, and encourages the fostering of inter-disciplinary, integrated design processes in urban design.

Biophilic design has been used in Western Australia to achieve outcomes for both water management and the wider sustainability aspects we’re seeking in this country.

These outcomes relate to the social elements framed within human needs and the improved functionality of the local environment.

Dunsborough, Western Australia

Plan view of two flood basins landscaped into the development as well as side treatment bioretention gardens.

The development of a residential estate upstream of the town of Dunsborough, south-west Western Australia, is a good example of how water management and landscaping can utilise biophilic design to achieve an improved outcome for the environment and community.

The development presented an opportunity to reduce existing flood risks to the existing township.

The project is in an area where regulatory authorities encourage developers to incorporate water sensitive urban design into their urban spaces.

Detailed water modelling showed that a series of large basins, stacked along the valley was a suitable engineering solution to accommodate stormwater runoff from the new development.

The basins were sized to accommodate existing deficiencies in the capacity of the downstream networks, up to and including the one percent annual exceedance probability (AEP) event.

The effect of the basins allowed a one percent AEP flow rate to be attenuated to that of a 20 percent AEP, to meet the capacity of the downstream infrastructure.

The issue, however, was that this series of ‘dams’ was both unsightly in terms of its position within a residential development, and offered little ecological value.

Alternative options were therefore investigated to see if this engineered solution could be enhanced using biophilic principles, which would turn the flood protection requirement into a wider communal, and ecological, asset for the development.

The review also looked at options to improve water quality, prior to the water entering Geographe Bay, a water body sensitive to nutrients and other potential pollutants.

Water is central to the human psyche, so it seemed logical to encourage the public to interact with the water – visually, audibly and physically.

When done well, the spaces created using biophilic design to treat and
channel stormwater can provide multiple benefits to residents.

The basins, roads and footpath networks were designed so that water could be seen and heard at multiple points.

An ecologically-functioning landscape that also matched human preferences was also seen as critical to the design.

This was achieved by maintaining sight lines over much of the space as well as incorporating particular points of interest.

This included using locally native plants to produce a low cover under feature native trees. Local stone is also utilised throughout.

This was complemented with areas away from main paths and houses, set aside for dense shrub planting, providing interest and critical variation in the landscape.

The placement of the plants was also designed to allow for water quality treatment and fauna habitat, while creating an interesting landscape that could be viewed from the main road into the development as well as residents’ houses and
local streets.

This solution created opportunities for residents to interact regularly with nature as they went about their daily lives.

Pathway network

The connection was enhanced with the construction of a network of pathways that offered easy walking and cycling options around the landscaped areas.

The pathway was designed to include nodes that invited people to explore the spaces further.

These pathways led to lookout points, as well as places where people could leave the path and interact directly with water.

High bushfire risk is part and parcel of residential housing estate design in Western Australia.

Low-fire-risk zones were developed, which included low native groundcovers interspersed with landscaped stone mulches.

These were designed with organic curves to reflect natural systems and also included feature rocks from locally
available material.

These mulch areas were carefully placed so they could also act as informal pathways that led directly from residents’ houses to the formal path network.

This area of stone mulch and low plants also allowed for view lines to be maintained for residents, providing passive surveillance to minimise risks of crime, while also providing people with a visual link to nature.

Overflow wetlands

View within wetland back to resident houses, highlighting open vistas.

A combination of bio-retention systems, as well as overflow wetlands, were used to improve the quality of the water as it flowed through the system.

The wetlands included a small low-flow channel to allow the upstream catchment water to move through without significant ponding and associated mosquito management risks.

This upstream water is relatively clean, as the upper catchment along the stream is heavily vegetated around the banks, and the current low intensive farming practices do not contribute high levels of nutrients.

For this reason, the current low ecological flows are allowed to drain through a vegetated low-flow channel.

This low-flow channel also provides a flowing water feature during most of the year.

Sight lines along this low-flow channel are maintained at key viewing points.

During larger rainfall events, the water spills into the surrounding wetlands for treatment and detention.

Stormwater from the developed areas flows into the bioretention systems first, where it is treated for most annual storm events (approximately a 63 percent AEP event).

The infiltrated water and runoff during larger storm events overflows into the wetland chain for further retention and treatment.

Liveability

Incorporating biophilic design into housing developments provides opportunities for integrating WSD with wider land development processes and considerations.

It also enhances the liveability of the people who live in those communities.

However, careful consideration is required so that the design process works with the regulatory framework and local conditions while also understanding the evolutionary preferences of people.

When done well, the spaces created using biophilic design to treat and channel stormwater can provide multiple benefits
to residents.

They can also achieve outcomes for the local natural and created environments such as increased habitat, water quality improvement and reduced effects associated with extreme weather events such as heat and rain.

These concepts, which are being used to such great effect across the Tasman, can easily be adapted by New Zealand engineers and urban planners. Calibre is working on a number of opportunities to incorporate these concepts across
New Zealand.

As increasing numbers of professionals and members of the public call for greater sustainability in urban design, this is just one way that we can move towards building cleaner, greener cities of the future.

• Brendan Oversby is Calibre Group’s manager, water and environment – Western Australia. Brendan.Oversby@calibregroup.com


This article was first published in the July 2018 issue of NZ Local Government Magazine.

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