AILA projects

Victorian Sites

Melaleuca Wetlands

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Landscape Architect: GbLA Landscape Architects

Project : Melaleuca Wetlands

Client: Wilbow Corporation

Location: Ferntree Gully, about 30 Km south east of the Melbourne CDB

Melaleuca Wetlands is located between Blackwood Park Drive and Waterford Golf Course, Ferntree Gully and once formed part of a larger flood plain area that received waters from Monbulk and Corhanwarrabul Creek within the larger Dandenong Valley.

Prior to European settlement the site would once have contained a rich diversity of flora and fauna typical of an area of Swamp Scrub where soils are poorly drained. The re-alignment of Monbulk Creek after the First World War combined with former farming activities and urban development during the 20th Century had the effect of eroding the ecological diversity of Monbulk Creek and the wider flood plain area.

The re-alignment of the creek created a concentrated flow of water over a sedimentary soil that had the deleterious effect of creating an incised channel that continues to erode today and is currently 2.5m deep in some areas. It also had the effect of significantly reducing the ability of the creek to provide silt deposition across the wider flood plain.

Ecological Significance

Areas of habitat for native fauna within and adjacent Monbulk Creek has been significantly modified as a result of the realignment of the creek combined with pressure for commercial and residential development within the catchment. Today only degraded remnants of vegetation exist along certain sections of Monbulk Creek in highly modified environments.

Monbulk Creek is one of only two systems in the Dandenong Valley which supports habitat for platypus (Ornithorhynchus anatinus) and water rats (Hydromys chrysogaster). A study of the section of Monbulk Creek adjoining the site by the Australian Platypus Conservancy (Williams, Serena: 2003) revealed that it contained the only substantial platypus population remaining in the Dandenong Valley Catchment.

A total of 56 platypus were identified within Monbulk Creek of which 30 – 40 platypus could be found at any given point in time in the creek system. Eleven of the 56 individual platypus identified within Monbulk Creek are known to have used the section of creek that adjoins the site.

The actual quantity of platypus using the creek has been identified as having a direct relationship to the available habitat within the area. An increased area of available habitat will ultimately result in greater numbers of resident platypus as well as creating a more balanced sex ratio of platypus within this and the surrounding area (Williams, Serena: 2003).

Wilbow Corporation has taken the opportunity to rehabilitate a portion (35 acres) of the former floodplain area, increasing the available habitat and diversity for numerous native species of invertebrates, fish, water birds and mammals. While at the same time effectively improving the quality of water within Monbulk Creek and satisfying a need for residential housing by providing 100 home sites directly north of the development.

Design Response

A series of online wetlands, braided streams, pond and riffles and a lake have been created to fulfil a number of functional hydraulic, ecological and public amenity outcomes.   The wider terrestrial landscape areas contains a 2.5m wide pedestrian circuit with boardwalks and a viewing deck allowing movement across the floodplain providing opportunities for viewing expansive areas of open water, dense stands of ephemeral planting and passive use of open space.

The design of the site has been guided by the Melbourne Water Waterway Activity Plan, an Environmental Management Plan, Hydraulic Studies, Geotechnical Investigations and design guidelines prepared by the Australian Platypus Conservancy.

Generally the Monbulk Creek system contains a number of constructed and cascading floodplain storage areas that can be broadly separated into two distinct hydraulic areas. The water quality treatment to the north of the site is essentially for the treatment of stormwater generated from the proposed residential development. The positioning of the wetlands, ponds and riffles within this area is based on the alignment of the former water course.

The second set of water bodies is located to the south of the site and contains a series of anastomosing braided streams separated by berms and rock chokes that are connected to a lake and pond and riffle areas that ultimately discharge into Monbulk Creek. The lake has been sited and designed to encourage platypus to create burrows in the side of the southern bank with steep batters (greater than 40 degrees). The design of the lake and its surrounds has been guided by the ‘Preliminary Guidelines For Design Of Lakes and Other New Water Bodies’ developed by the Australian Platypus Conservancy.

Both systems contain extensive areas of ephemeral planting designed to trap suspended solids and coarse organic material. It is anticipated that the development will increase the overall numbers of platypus within Monbulk Creek and help to balance sex ratios of Platypus within the creek.

Environmental Outcomes

The creation of greater connectivity of Monbulk Creek and the adjoining floodplain from base flows to the 1yr ARI flows.

An improved and natural source of organic carbon to downstream ecosystems. It is anticipated that the phosphorus load of side casting flows from Monbulk Creek will be reduced by up to 50%.

The creation of a more ecologically diverse waterway habitat for invertebrates, fish, mammals and bird life.

Treatment of stormwater from the associated catchment and from a 30ha catchment upstream of Monbulk Creek through the collection of suspended solids and coarse organic material.

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2006