New South Wales Projects & Sites
Rouse Hill Landscape Restoration of Riparian Corridors and Stormwater Infrastructure
introduction / case-study report / overview / images / location / Projects
Landscape Architect: EDAW AECOM
Location: Rouse Hill (Sydney) New South Wales
As listed as A Case Study for the AILA's 2008-2009 National Climate Change Project
Case Study Overview
EDAW AECOM has contributed to the riparian restoration of 16 hectares of stormwater infrastructure works for Stage 3 of the Rouse Hill Development Area in Sydney’s north-west growth sector.
Landscape restoration works included 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, comprising some 50 species.
EDAW guided the design process for detention basins and new watercourses to accommodate the one-in-100-year flood and fully-structured natural communities (with 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 urbanised 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 stabilisation, 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.
Innovative Approaches
Planning and Pre-Design
- A landscape rehabilitation plan prepared at the concept stage of the project ensures design input into engineering works to maximise landscape restoration outcomes.
- Careful management of works area edges protects them from adjoining subdivision construction works; robust fencing protects the 1-in-100-year floodplain boundary; boundary weed management measures guard against adjoining weed sources; and knowledge sharing with individual developers ensures correct installation drainage infrastructure into the corridor.
- Provision of one hectare of compensatory landscape restoration planting area and one hectare of bush regeneration area offsets unavoidable losses of native vegetation on a one-to-one basis (for example, in areas along pipeline routes where trees were not permitted to be planted).
- Training in on-site soil stripping by a specialist soil scientist was provided to all contractors.
Design and Management
- Sizing of detention basins contains the 1-in-100-year flood, as well as a complete cover of fully structured plant communities.
- Sizing of channels conveys flood flows, while containing fully structured riparian communities.
- Specialist soil stripping, stockpiling and reinstatement processes by soil horizon reinstates natural soil landscape characteristics and buffers the bushland restoration works from hostile sub-soil conditions.
- Relatively high species diversity (50 species), all of local provenance.
Monitoring and Evaluation
- Creation and monitoring of a one-hectare experimental native grass direct seeding plot assesses the potential of the process to provide a simple and low cost alternative to initial site stabilisation, weed suppression and conventional mass planting landscape restoration approaches.
- Monitoring and reporting on landscape restoration to basins and channels at three-monthly intervals measures outcomes against key restoration goals. Monitoring is undertaken using a field GPS-GIS data collection unit, which quickly and accurately describes key monitoring criteria.
Budget: $2.5 million Lessons Learned
- Benefits of soil stripping and reinstatement to protect against chemically hostile sub-soil conditions and remove the need for the importation of soils
- Importance of securing site boundaries to weed invasion and physical intrusion
- Need for initially intensive weed management, which then tapers off to very minor levels towards the end of the contract period
- Importance of achieving quick, dense plant cover to resist weed invasion and achieve a relatively self sustaining community within a relatively short Plant Establishment Period (typically never more than two years), suitable for handover to a long-term land owner or manager
- Identification of core suites of hardy, quickly establishing species that are suitably representative of the desired plant associations
- Capacity of native grasses to quickly take up planting gaps, with successive generations of germination from the initial planting occurring within a two-year Plant Establishment Period
- Importance of regular monitoring of restoration outcomes through the Plant Establishment Period, including species diversity, relative performance of individual species, changes in plant density and cover over time, and key weed species of concern to guide on-going decision-making process
- Value of regular photographic monitoring, which, for example, can provide reference dates against which the extent of damage from adverse environmental incidents can be assessed, such as the extent of plant losses incurred due to a major flooding event
- Benefits of incorporating experimental design into projects, which can provide substantial information for the development of innovative approaches to future projects (relatively inexpensively)
- Benefits of undertaking a critical review of the project upon completion, to document typical problems and how, with hindsight, these can be overcome in future projects
Project Team: EDAW AECOM
Mark Blanche, Kate Guthrie, Andrew Derkatch, Glenn Bird, Stuart Martin
Client
Australian Water – Dr Bob Staib, Development Manager
Landscape Contractor
Simpson Landscapes – Steve and Glenn Simpson
Soils Specialist
Sydney Environmental and Soil Laboratory – Simon Leake
Direct Seeding Specialist
Cumberland Plain Seeds – Tim Berryman
Bush Regeneration Specialist
EcoHort – Edgar Freimanis
introduction / case-study report / overview / images / location / Projects
uploaded April 2009
