"The approach has the potential to facilitate a new low-cost, longer-term approach to broad acre landscape restoration..."

New South Wales Goes Bush

Two projects in the Sydney region of New South Wales, Australia showcase innovative ecological restoration and design techniques, and show the role that ecology can play in community and economic development. The Rouse Hill Development Area is located in Sydney's northwest growth sector. In what will be a highly urbanized zone, the riparian restoration of 16 hectares of stormwater infrastructure will manage heavy water volumes and reinstate ecological communities. In the Hunter Valley, 120 kilometers north of Sydney, the development of a 1,000-hecatre industrial estate has been conceived as 'industry in the bush,' rather than an industrial estate with green landscaping. Both projects will conserve local flora and enable built environments to cooperate with natural systems.

Rouse Hill
AECOM's landscape restoration works include bushland reconstruction and regeneration to all areas within the 1-in-100-year flood zone, incorporating channel reconstruction, detention basins and bushland remnants. Most of the works area has been under agricultural management since the early 1800s, and therefore has a very high weed seed load.

The works aim to restore plant associations characteristic of the two endangered ecological communities that inhabited the site prior to European settlement: Cumberland Plain Woodland and River-Flat Eucalypt Forest. All plant material used is of local provenance, with a total of 1.7 million plants installed, including some 50 species.

Our team of environmental specialists guided the design process for detention basins and new watercourses to accommodate floodwaters and fully-structured natural communities, including full ground, shrub and mid-stratum layers and canopy. New site soil stripping and reinstatement processes were developed for the project to conserve important existing soil landscape properties and buffer the works from chemically hostile sub-soils. Only site soil was used throughout the project.

Some 15 months into the plant establishment period, the restoration works are exhibiting substantial species diversity and excellent plant cover, as well as substantial germination from the first year of seed drop. Restoration is on track to create a low-maintenance, relatively self-sustaining and diverse locally endemic plant community within what will be a highly urbanized setting.

Additionally, a one-hectare experimental plot has been established to monitor the direct seeding of a select suite of native grasses, to assess the potential of the process to provide a simple and low-cost alternative to initial site stabilization, weed suppression and conventional mass planting landscape restoration approaches. Results so far are encouraging, with several species exhibiting excellent plant cover, germination of off-spring and weed suppression characteristics. The approach has the potential to facilitate a new low-cost, longer-term approach to broad acre landscape restoration, in lieu of current mass planting practices. The results of the experiment are being documented and will be submitted for publication within scientific literature.

Hunter Economic Zone
To realize the vision of 'industry in the bush,' the design prioritizes strategies to maintain the integrity of the natural context. A strategy of stormwater harvesting on individual lots and at the cluster scale will maintain runoff volumes at close to pre-development levels, conserving the existing ephemeral hydrologic regime and site ecology, including the habitat of the endangered Green-thighed Frog. During times of heavy rain, swales and detention storages will buffer and slow stormwater runoff to protect local creeks from erosive flows. Where the underlying soils are conducive to infiltration, French drains and infiltration areas will encourage groundwater recharge. On-site detention basins on each lot attenuate flood flows and prevent the development from flooding downstream areas. No net increase in the 100-year discharge will result from the site's development.

Using only plant material of local provenance mitigates dilution of the local bushland gene pool. A site-specific handbook identifies locally indigenous species that are aesthetically appealing, reliable to cultivate and cost little to grow, maintain and replace. A plant procurement database compiles all information required to collect, propagate and plant vegetation to inform future work by developers and landscape architects alike.

Specialist soil stripping and reinstatement processes will help regenerate bushland across the development, exploiting the viability of the burgeoning native soil seed bank sourced from local lands. Direct seeding of local provenance native grasses supplements these processes. Studies on-site show a high success rate for bushland regeneration from relocated topsoil. This offers a relatively inexpensive and effective landscape restoration solution to deal with road verges, embankments and other areas of development within the Hunter Economic Zone.

This landscape restoration approach requires a coordinated and informed civil contracting team to maximize conservation outcomes and to apply the methodology of topsoil stripping and reinstatement without compromising the fragility of the site topsoil. Plant operators and supervisors learn soil types, soil horizon depth and stockpiling techniques during on-site training sessions.

Road networks not only connect with nearby townships; they form an environmentally and economically efficient network to service the greatest number of lots with the fewest roads and creek crossings. Road networks follow existing watercourses, where possible, forming bushfire protection zones, bushland management boundaries, and stormwater management corridors before discharging into conserved natural watercourses.

Landscapes for learning
Australia's New South Wales Department of Environment and Climate Change's National Parks and Wildlife Service is formally monitoring the outcomes at the Hunter Economic Zone. Meanwhile, Mark Blanche, AECOM Sydney's environmental director, and colleagues led a series of tours of the Rouse Hill site for more than 80 visitors from New South Wales industry and government to showcase the successful restoration practices underway. Both projects were included as case studies in the Australian Institute of Landscape Architects (AILA) Climate Change Adaptation Skills for Professionals Program.

Jake Herson, Kim Murphy