There are many ways in which green infrastructure, such as green roofs, can have a positive environmental impact beyond the site itself. It can be used, for example, to manage stormwater and conserve biodiversity.
These impacts might be quantified and reported on as part of the planning and design process, particularly in the case of stormwater management and water sensitive urban design. But it is possible to go further and tell a story about the landscape and how the green infrastructure fits into it. Among other uses, it can be used as a marketing tool, for a big-picture appreciation of green infrastructure. The story should cover:
- Origins and evolution of the landscape, drawing on geology and geomorphology
- Land use history, from Aboriginal use of the land to industry and urbanization, if relevant
- Waterways – identifying local creeks, rivers and lakes, and assessing their general health
- Landscape ecology – how animals and plants are interacting with, and moving through, the landscape
Here are three brief, real-world examples, taken from three different Melbourne landscapes, with a primary focus on waterways:
An apartment building in West Footscray
In Melbourne’s west, a planned apartment building in West Footscray includes a proposed green roof and other green infrastructure. The site is at the eastern edge of the third largest volcanic plain in the world, which covers a vast area of southwest Victoria. By Australian standards, the basaltic plain is a young landscape.
Stony Creek has been making its way through this basaltic plain for thousands of years, and passes within a few metres of the site of the apartment building. The Marin-Bulluk people used the creek as a meeting place and as a source of food. Since European settlement, Stony Creek has felt the full impact of industry and urbanization. It is one of the most polluted waterways in Victoria and it is so modified that, in parts, it is essentially just a fast-flowing drain.
About eight kilometres from its modern-day origins in Sunshine, the creek joins the Yarra River at Stony Creek Backwash, underneath the Westgate Bridge. Of the Yarra River’s 50 or so tributaries, Stony Creek is the last to join the river before it flows into Port Phillip. One of the most important functions of the green infrastructure at the apartment building, therefore, is the way it manages both the quantity and quality of stormwater that leaves the site for the creek (requiring implementation of design, management and maintenance considerations).
The site, and its green infrastructure, is also well placed to protect local biodiversity. Prior to European settlement, the area around the site was open grassland, with riparian vegetation around the creek itself. Close to the site, there are still some native trees and shrubs on the southern bank of the creek. The green infrastructure on the building will help the creek to function as an urban wildlife corridor that links Stony Creek Backwash (now a nature reserve known for its mangroves and waterbirds) to a reserve in Sunshine.
A school in South Yarra
Another location, this one in central Melbourne, features the existing green infrastructure of Melbourne Girls Grammar School. It includes a green roof, installed in 1987, at the heart of the campus.
The school is positioned just south of the Yarra River, on the eastern edge of the Royal Botanic Gardens. The lakes of the Botanic Gardens are remnants of a natural water system, and still provide habitat for many animals and plants. The system has recently been revitalized as part of a project called Working Wetlands, with the purpose of reducing nutrients entering the lake system and the Yarra River.
Stormwater from the school flows into the storm drain on Anderson Street, and from there it is now diverted into constructed wetlands before moving on to Ornamental Lake. By complementing the water-sensitive design of the Botanic Gardens, the school’s green infrastructure can improve the health of the lake.
This benefits the Yarra River too, into which the lake overflows. The school’s green infrastructure also protects the Yarra in a more direct way. The school sits on a relatively young layer of sedimentary rock, and is elevated up to 40 metres above the river on a fairly steep slope. In heavy rainfall, an ephemeral stream emerges from the rock below the building that houses the 1987 green roof, and then flows down the steep slope to the river. The green roof captures runoff that would otherwise become flow in this stream.
A house in the Dandenongs
The final example, out east, is Anton Engelmayer’s stunning home, perched on a steep slope in the Dandenongs. The Dandenongs are the remains of a huge, long-extinct volcano, last active when Australia was part of the Pangaea supercontinent. It has been dissected by creeks over many millions of years to form a series of ridges and valleys. It is a much older, higher and steeper landscape than the basaltic plain of the first example. The house adapts to the gradient and the hard volcanic rock below with a stepping design.
The house is also covered in green infrastructure, including a green roof and a raingarden, which are part of a sophisticated stormwater management system. Particularly given the absence of local storm drains, the green infrastructure helps protect the slope itself from the erosive effects of stormwater. Meanwhile, the health of the creek at the base of the slope benefits from the reduction in volume of stormwater that reaches it, and from the greater cleanliness of that stormwater.
For example, the creek is home to a near-extinct crustacean, and less urban stormwater (which is the main threat to its existence) is a positive step towards saving it, particularly if other homes in the catchment adopt a similar approach to stormwater management. The indigenous plants grown in the home’s green infrastructure are also doing their bit for local biodiversity.
Stories like these can give green infrastructure context in terms of both space and time, and they can be used to communicate the value of green infrastructure. After all, green infrastructure is neither cheap nor simple, and it requires ongoing management and maintenance. It is a significant long-term investment, and its environmental value can be tougher to sell than its social and economic value. Nonetheless, it is very important. The success of our efforts to build more resilient and liveable cities will depend, in part, on how successfully we are able to bring nature back.