Mamu Rainforest Canopy Walkway
- An iconic, world class tourism facility in Wooroonooran National Park
- Provides a highly attractive tourist experience of the rainforest canopy, Ma:Mu culture and a panorama of the North Johnstone River valley
Location: Wooroonooran National Park, East Palmerston
Year Completed: 2008
The Mamu Rainforest Canopy Walkway is a unique construction project set on the edge of the Wooroonooran National Park in Far North Queensland. The project is located on the Palmerston Highway, approximately 25km west of Innisfail. The Canopy Walkway is an unrivalled tourist attraction, offering all visitors a unique capacity to explore and experience the Wet Tropics natural heritage and Aboriginal cultural heritage values of the region.
This project is the culmination of a lengthy process which began in the late 1990s as an idea. Through the perseverance and foresight of many companies, individuals, the State Government and the land’s Traditional Owners, that idea has been brought to a spectacular realisation.
The end result is an impressive facility, unique to Far North Queensland, which boasts over 1 km of on-grade footpath through the rainforest, approximately 370 metres of elevated walkway perched along the edge of the Johnstone River Valley, a 40 metre high canopy viewing tower and an eight metre long cantilever tower, both of which provide spectacular views into the adjacent river valley. The project also features a variety of auxiliary buildings and supporting infrastructure, including a bus and car park, interpretative nodes and shelters throughout the facility, and modern office and ticketing facilities.
PLANNING AND MANAGEMENT
Essential to the spirit of this venture was the preservation of both the delicate rainforest and the cultural heritage it sustains. Innovative engineering was paired with a sensitive concern for this wilderness. This averted environmental damage during construction – and the design also minimises any risk of future harm in the event that the facility requires maintenance or repair works.
The area’s traditional owners, the Ma:Mu people, were consulted at every turn so that the walkway development would remain in keeping with their spiritual affinity to the rainforest. Stakeholders such as the Johnstone River Ecological Society and the Innisfail Disability Focus Group have been consulted during the planning and construction phases in order to ensure their concerns and needs could be accommodated.
The environmental sensitivity of the project site called for the adoption of a robust Environmental Management Plan (EMP), which formed the framework for the set-up and management of the site. It included a stormwater management plan, as well as erosion and sediment control principles adopted during construction.
The EMP was developed by Arup, in partnership with the Environment Protection Authority (EPA) and Hutchinson Builders. It was based on the recommendations of the Impact Assessment by Natural Resource Assessments, detailed botanical survey by Regal Jensen and Cultural Heritage Assessments by Nicky Horsfall. It was developed from a brief provided by the EPA, and through close co-operation with the construction team was able to strike a balance between necessary environmental protection, the practical limitations of the site and the adopted construction methods.
The project site was selected due to its access, vistas, and environmental and cultural heritage values that could be interpreted by the facility. The site is an iconic, world class tourism facility providing a highly attractive tourist experience of the rainforest canopy, Ma:Mu culture and a panorama of the North Johnstone River valley.
The site encompasses some vacant, previously cleared farmland on which the car-park is constructed, as well as a portion of rainforest at the edge of Wooroonooran National Park. The amenities and entry structures are located on the edge of the rainforest, while the on-grade walkway, some covered nodes and the feature structures are all located wholly within the rainforest.
The tower structures were sited to minimise clearing of vegetation which meant utilising existing clearings and areas of badly damaged vegetation as a result of Cyclone Larry.
Significant physical constraints included restrictions on the size of the access track within the rainforest, very limited opportunities for clearing forest vegetation, very steep and heavily vegetated terrain local to the feature structures, and the prevailing local weather conditions, namely prolonged periods of rain and high levels of humidity.
Key client requirements included a facility which provides a 50 year design life (subject to appropriate maintenance), ease of maintenance, relative ease of repair and the ability to accommodate for disabled access. Additionally, flexibility was desired in the event that one portion of the facility was to be damaged in severe, cyclonic weather.
Constraints on the design included the limits to crane location, capacity and reach, as well as the need to develop solutions featuring modular designs, repeatability of details, and ease of fabrication, construction and installation.
Hot-dip galvanised steel was the material chosen for the primary structural elements of the feature structures, for reasons of economy, strength, durability, and flexibility in terms of fabrication and construction. Pedestrian balustrades were also constructed of hot-dip galvanised steel sections.
The elevated walkway design features circular tower tops and short bridges that wind their way between existing trees, and were able to be installed with minimal disruption to the rainforest.
The trafficable, wearing surfaces of the walkway and towers were constructed by using a recycled plastic decking product by Replas. This product exhibits qualities such as durability, ease of installation, minimal maintenance requirements and appropriate reserves of strength.
The atmospheric corrosivity of the site’s environment was a key influence in a decision to utilise open steel sections, rather than hollow sections. Such a choice significantly reduces the risk of failing to identify the onset of corrosion, as part of a maintenance program for the structures. Similarly, attention was paid to the orientation of members. Sections were down-turned where possible, to minimise areas where debris may build up, and therefore further reduce the risk of premature corrosion.
Environmentally sustainable, durable and low maintenance materials were selected.
Unpainted galvanised steel was used for the primary structure of the elevated walkway, cantilever tower and main observation tower— requiring only occasional cleaning for ongoing maintenance, and reducing the risk of contamination of the rainforest through leaching or flaking of paint.
‘Enduroplank’ by Replas and Gough plastic products are used. The recycled plastic decking was used for the elevated walkway decking. The equivalent of over 900,000 plastic 2-litre milk bottles diverted from landfill was used in the walkway decking.
Recycled plastic is also used on some of the wall cladding of buildings, seating and along walking tracks as tap rails for vision-impaired visitors.
Power supply to the office areas is supplemented by a roof-mounted 2 kilowatt solar panel system.
Lighting in the walkway shelters is provided by solar-powered lights.
WATER AND WASTE
Hybrid composting toilets reduce impacts on water quality at the site and reduce overall water use. The micro-flushing toilet feeds directly into a primary treatment tank filled with water. Solids are broken down by bacteria and clarified effluent is delivered to a secondary treatment tank where further bacterial action completes the treatment. The effluent is then discharged into a holding tank for removal.
The civil engineering design of the car-park features a Gross Pollutant Trap designed to capture and retain gross pollutants, litter, grit, sediments and associated oils.
At the project’s formal opening, the then Queensland Premier Anna Bligh called it “Nothing short of spectacular”, with its awesome views over rainforest-clad mountains, rock gorges, river rapids and the strong links with the traditional land owners.
Base building architect/ designer: Woodhead International
Civil, structural, traffic, environmental engineers: Arup
Hydraulic engineer: Gilboy Hydraulic Solutions – Hydraulics,
Electrical and mechanical engineers: MGF
Geotechnical Engineering consultants: Golder Associates
All Construction Approvals: Building Certifier
Builder: Hutchinson Builders
Impact Assessment: Natural Resource Assessments
Detailed botanical survey: Regal Jensen
Cultural Heritage Assessments: Nicky Horsfall