Australian Water Management Review Vol 2 2013 | Page 93
Naturalisation Project
Cooks River
an artist’s impression of what the Cooks River will look like after the naturalisation process.
T
he Cooks River is located in the inner south west of Sydney. It runs through some of the most heavily urbanised and industrialised areas of Sydney, before flowing into Botany Bay near Sydney Airport. The Cooks River Improvement Act 1946 resulted in the concreting of the riverbanks to reduce flooding and ‘improve’ the condition of the river. As a result, many sections of the river today resemble a concrete drain and the river is considered one of the most polluted in Australia. Management of the Cooks River and its 102 km2 catchment is shared between 13 local councils and various state government agencies, including Sydney Water. The complexity of this shared responsibility makes it difficult to address environmental and social concerns strategically and holistically, to the frustration of the local community. Sydney Water owns significant portions of the Cooks River’s main channel. These sections are generally trapezoidal channel, with concrete bed in the upper sections and natural bed in the tidal section. Sydney Water implements an ongoing inspection, maintenance, repair and renewal program for all its stormwater assets. These inspections identified sections of the Cooks River’s concrete banks that had deteriorated to a point where renewal was more economical than repair works. Sydney Water explored renewal options capable of restoring some environmental values to the riparian zone and improving the social amenity of the foreshore. The preferred option was to ‘naturalise’ the deteriorated sections. This involves removing the concrete, reshaping the bank to reduce its slope, and stabilising it with native plants and sandstone. Naturalisation is only possible where constraints permit, such as availability of adjacent land, location of underground services and hydraulic capacity of the channel. Significant investigations and comprehensive stakeholder engagement were required to make an informed options assessment. Sydney Water took a proactive and inclusive approach to the background investigations by taking
community groups. These concepts were then distributed to over 5,000 residents along the river. A survey to determine the level of support for naturalisation rather than concrete renewal was also distributed. Over 96% of respondents supported naturalisation. The concept designs were finalised through workshops with key stakeholder groups and public submissions. Designs for all sites include removal of the existing deteriorated concrete banks, laying back the banks to reduce slopes, and stabilisation with sandstone and local endemic macrophytic and terrestrial plants. The threatened ecological community ‘coastal saltmarsh’ will also be established at the two intertidal renewal sites. At one site – called Cup and Saucer Creek - the adjacent open space has enabled the inclusion of a 0.25 hectare offline wetland to provide additional habitat and help reduce pollutants entering the river. Sydney Water approval was granted in October 2009 to proceed to detailed design. The total project is anticipated to cost $8 million. It is hoped that the project will set a new benchmark for riverbank restoration in Sydney and a precedent for future stormwater renewals, as over the coming years, Sydney Water has proposed to renew as much of the river bank as possible using the naturalisation method. The areas to be naturalised will be subject to approvals, available funding and community support. This project follows a $6 million spend last year on removing 10,000 tonnes of sediment and other waste in the river. This significant investment improved the flow and health of the river, which has reduced the risk of flooding. Local residents, Canterbury Council and NSW Fisheries cooperated with Sydney Water and Veolia Water Network Services to complete the project, which is [art of a broader five-year maintenance program to improve the stormwater system and protect public health and the environment. Since 2009/10 Sydney Water has removed over 2300 cubic metres of rubbish and 1500 tonnes of sediment from its 14 gross pollutant traps in the Cooks River Catchment.
Australian wat e r m a n a g e m e nt r e vie w 87
The silt removal which took place last year. a leadership role in the strategic planning and inviting local Councils and other stakeholders to be involved and benefit from the work it is undertaking. By doing this, Sydney Water has developed valuable relationships with ?????????????????????????????????M????]???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????
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