Australian cities are evolving from a low density suburban model to more varied forms. This is due to the rapid development of higher density centres with apartment living, supported by improved public transport, in the major cities where employment and education opportunities are greatest. This new development model is most pronounced in the larger cities of Sydney Melbourne and Brisbane.
Infrastructure for cities is expensive, especially in low density growth areas on the urban fringe of larger cities. While it is still a matter of debate in Australia, the carbon footprint of even well planned suburban growth is significant and arguably beyond our means if all factors are accounted for.
The higher level of access to services and employment that high density city living offers has seen a dramatic shift in the last year or two, with higher density new housing now starting to dominate for the first time in our history. Under the suburban development model, green space is often properly allocated with natural areas preserved, drainage systems well planned and space provided for active and passive parkland, new schools and trees planted along most streets. Traditionally, detached housing has been large enough to accommodate front and back yards that have been used as garden space.
However, this form of development is coming under pressure, as houses get larger and lots get smaller to allow private land developers to continue to make profits.
Green infrastructure in cities
A 2014 study of Australian cities and towns called ‘Benchmarking Australia’s Urban Tree Canopy’ was undertaken by the Institute of Sustainable Futures, (IFS) at the University of Technology, Sydney (UTS) using sophisticated GIS software developed by the US Department of Agriculture and Forest Service.
139 Local Government Areas, (LGAs,) where almost 70% of Australia’s population lives, were assessed using air photography to determine tree canopy cover, shrubs, grass and hard surfaces. Dramatic variation was recorded from LGAs with nearly 80% tree canopy cover to the lowest cover measured at just 3%. Average canopy cover was 39%. Australian settlements have widely varying densities, soils and climate from tropical to desert to cool temperate. Since most of these areas would benefit from an increase in canopy cover, an ambitious campaign is underway to achieve a 20% increase of green space in LGAs by 2020.
The benefits of trees and plants are becoming clear in terms of human health and happiness, as well as the mitigation of floods, air and water pollution, and extreme summer heat. Climate change will effectively increase extreme weather events including floods, drought and longer periods of extreme temperatures. Extending tree canopy in urban areas takes time to achieve because of the need for planning, funding and growth of the trees that may not reach their peak for decades to come. The time for action is now so that we are in a better shape when the effects of climate change become more pronounced by mid-century.
These components of the city are often functional spaces with their design determined by engineering parameters. However, we are beginning to realise that most major infrastructure projects have the potential to incorporate green elements that add great value for the community in the long term, especially if they are part of the brief and budget from the outset, rather than an afterthought.
Green infrastructure can mean many things
Open space in the form of public parks and nature conservation areas are the most obvious opportunity for green infrastructure. Open spaces take many forms from sporting areas to heritage gardens and areas of untouched nature that may not have many visitors. They all add value to cities.
A research project called ‘Smart Parks’ produced by Soofa (an MIT-based research company that specialises in research and developing products for Smart Cities) in 2016, investigated money spent on open space across many US cities and found a 20-fold return on investment when all benefits were calculated. These included increased property values, more tourism, less air pollution, improved mental health and physical health, utilisation of storm water, social capital and park access and connectivity. This work creates an economic argument for investment in urban parks in order to maximise their benefits.
Green transport infrastructure
Freeways are a good example. They can be designed with landscape that treats collected storm water, controls views and noise, provides safe pathways for pedestrians and cyclists and creates shade habitat and corridors for wildlife with minimal extra land take.
Major roads can be designed as tree-lined boulevards that provide shade and a comfortable safe environment for pedestrians and cyclists with active street life along their boundaries. Storm water can be captured, treated and allowed to re-nourish groundwater to help support trees and other planting that in turn will cool the local environment and help clean the air. The benefits of such an approach to road design extend greatly beyond transport economics to include improved human health and mental well being, enhanced property values with consequent increase in rate revenue for government.
Smaller roads, streets, car parks and pedestrian spaces should all be considered for greenery and especially canopy trees when they are developed or even retrospectively. Trees in urban areas can take space, conflict with services and cause damage and they do need care in selection, installation and ongoing maintenance but the benefits will normally greatly outweigh any costs.
City drainage systems
All cities, towns and suburbs need a system for collecting and managing storm water that falls on, or drains through, urban areas. Conventional engineering practice usually focuses on hydraulic efficiency. This often means using pits, pipes and concrete-lined drains to remove water from rooftops and city streets as quickly as possible. We are now learning that systems that retain and treat water at the source can have multiple benefits if well designed and maintained. Drainage reserves can be multi-purpose. They can be useful green spaces that provide sporting and natural areas with walking and cycle paths along their length. They may occasionally go under water in peak events but most of the time they will be improving people’s lives in many ways. Money spent on concrete pipes and channels will often be much better spent on grass, trees and pathways and maintenance.
Ecological corridors
Some Australian cities include one or more catchment management authorities that have the responsibility of managing waterways across all or part of a city, or beyond it, covering areas that harvest water for storage and supply as well as rivers and drainage systems across many local government boundaries to the sea. They have the responsibility to ensure water quality, manage flooding and protect the ecological health of the land they regulate and manage. They act as coordinators across local government boundaries to help the continuity of these ecological and recreation corridors so the benefits to city residents are maximised. Catchment areas are assessed and mapped for ecological health to assist prioritization of works and local government is assisted with grant applications for projects like path systems and re-vegetation projects that are often carried out with the involvement of schools and other community groups.
Private gardens, roof gardens and green walls
These are all opportunities to add to the green networks of the cities. They are not normally infrastructure in themselves but they have the effect of reducing the need for infrastructure of many kinds, from reduction of storm water runoff in peak events, to reducing the need for heating and cooling buildings, to climate modification of the local environment and improving urban air quality.
Private gardens within housing of all types can be designed with lawns and planted areas that capture and absorb water from roofs and pavements. A range of techniques for ground water recharge within gardens is possible.
Trees, vines and shrubs within private gardens can beneficially modify indoor and outdoor climate thus saving energy. Gardens can also be a source of food for residents and gardening is well known for its health and therapeutic benefits.
As cities become denser, private gardens are under pressure and alternatives like balconies, roof gardens and communal garden spaces are being seriously explored. These can be simple or technically complex, but rewards are significant where they can be provided and maintained.
Planning and funding green infrastructure in cities
The economic and social benefits of delivering green infrastructure across our cities are becoming better understood. However, most often infrastructure projects are defined and delivered within restrictive parameters that come from established professional silos of project definition and management.
With this in mind, the Australian Institute of Landscape Architects (AILA), together with green industry businesses and associated professional organisations, have formed the Living Cities Alliance that has framed a National Five-Point Living Infrastructure Plan that seeks to encourage sustained investment in green infrastructure across the country.
Scotland already has such a plan in place, which will fund 15 significant green projects across the country in 2016. (‘Green Infrastructure Scotland’ is funded by the European Regional Development Fund.)
The key seems to be creating awareness in all levels of government and those in the private sector in developing cities, about what is possible and how it should be integrated into thinking about existing and future cities.
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