Water Sensitive Urban Design (WSUD) installations aim to rehabilitate, maintain and protect remaining coastal and riverine ecosystems, considering the challenges faced through ongoing development and competing interests.
Little McCreadys Creek and Lagoon Creek were chosen as suitable sites for developing and showcasing best practice methods for improving stormwater quality, rehabilitating waterways, enhancing aquatic habitat, and improving the ecological corridor. Investigations informed each design and included a review of background information, a geomorphic assessment, flood modelling, landscape assessment, stormwater quality modelling, and consultation with community members and other stakeholders.
Both creeks were assessed as adjoining open space that had, in the past been substantially altered through agriculture and urbanisation. Each site retained many environmental values including native fauna, fish, frogs, and some native vegetation, however ecological surveys suggested poor water quality and lack of habitat was limiting species abundance and diversity. In both cases, the creeks and adjoining parklands are highly valued and regularly used by the community for passive and active recreation. Increasing urban development within each catchment will change the creek hydrology and sediment supply, however flood modelling shows that significant rehabilitation works can be undertaken without any adverse effects on private properties.
Moreover stormwater modelling demonstrated that introducing more riparian and wetland vegetation could make improvements in water quality. Rehabilitation of Little McCreadys Creek and Lagoons Creek have substantially improved the ecological condition and water quality entering Sandringham Bay while improving public amenity.
Little McCreadys Creek
Little McCreadys Creek is a modified urban waterway corridor at the headwaters of McCreadys Catchment, surrounded by residential land. The creek retains remnant Melaleuca leucadendra and is upstream of a continuous vegetated riparian corridor. The corridor is highly utilised and well considered by the community. Threats to the creek include channel modification (exacerbating erosion), stormwater runoff, fragmentation, invasive weeds and limited habitat features.
Improvement works included the installation of four wetlands, four fishways, refuge pools, and instream habitat features (including wetland and instream planting). Such works enhance the riparian corridor by providing habitat connectivity, increasing biodiversity, improving filtration (buffer), reducing runoff velocities and improving the amenity of the creek.
Terrestrial revegetation and weed control works complementary to the habitat improvement works include: improving water quality (filtration and reduce runoff velocities); improving instream environments (shade, ph, leaf litter inputs, filtration capacity etc.,) stabilising sediments (mitigate erosion); increasing habitat and structural complexity; and, improving the visual amenity, community connection and ecosystem service values. Instream vegetation also acts to intercept marine debris and pollutants and prevents future deposition into the downstream environments. Weed control works facilitate vegetation establishment and recruitment and assist in increasing connectivity, habitat and refuge within the headwaters of this catchment.
Lagoons Creek is a highly modified tributary of the lower Pioneer River and Lagoons Creek (Stage 2) and is situated immediately upstream from the freshwater/estuarine interface of lower Lagoons Creek (Stage 1). The greater Lagoons Creek Catchment encompasses nearly 600ha, of which 20% is urban land use. Increased urban development and agricultural farming practices have impacted the watercourse through vegetation clearing, channelisation and straightening. These impacts have resulted in sediment deposition, exotic weed proliferation and subsequently, fragmented the creek into sections of discontinuous waterway. Loss of instream connectivity impacts aquatic species migration.
Stage 1 improvement works established a rock lined open channel drain, three rock-ridge fishways and a riparian corridor linking fresh and marine waters. Stage 2 involved the re-creation of a paleochannel, installation of two wetlands, three fishways and the extension of the vegetative corridor, permanently linking existing freshwater lagoons to Pioneer River. Installation of multiple fishways at the freshwater/marine water interface is of vital importance to the life cycles of many native migratory fish species (e.g. tarpon) opening suitable breeding ground for native migratory species is of significant environmental, recreational and commercial value to the region. Installation of 10-15,000 indigenous species in a formerly denuded landscape will assist in bed and bank stabilisation as well as increase biodiversity and connectivity and improve instream environments. Recreating a riparian corridor, and the subsequent ongoing weed control works will facilitate revegetation and recruitment over initial years (3-7 years), where, it is anticipated that, weed control works will lessen over time as the native canopy and other strata establish. Works will improve stormwater quality, fish migration and improve the environmental and aesthetic values of lower Lagoons Creek.
Gross Pollutant Traps
A total of 44 gross pollutant traps were installed between 2013 and 2016, over the course of the Urban Reef Rescue Project. Three trash racks were installed in the Cannonvale Botanic Gardens to isolate and retain inorganic material (namely litter) and reduce the amount of organic material (which contains/captures microscopic pollutants) entering Pioneer Bay. Forty-one litter baskets were installed in Mackay’s CBD stormwater pits to capture waterborne pollutants drained across the stormwater network. Litter baskets are lightweight, uniquely designed with a by-pass and net, and angled so drainage flow in high rainfall events is not impeded. Furthermore, each basket is viewable from the street; significantly reducing the maintenance burden on council street sweepers. Based on similar examples in the region, it is expected that the 41 litter baskets will capture one tonne of debris every quarter. Six wetlands were installed within Mackay, with four installed into Little McCreadys Creek and two into Lagoons Creek.
Community Clean Up Events
Numerous Coastal Clean Up and Clean Streets and Creeks events were held across the region over the course of the Urban Reef Rescue Project. The premise of these events is to increase community awareness and involvement in preventing land based litter from entering the marine environment. The clean-ups targeted coastal beaches and urban hot spots for gross pollutants (i.e. urban stormwater outlets draining into the GBR lagoon). Key outcomes include –
- removal of land based litter from urban coastal environments (and prevention of marine debris)
- community engagement activities to raise awareness of the impacts of urban litter and stormwater on reef water quality
- date collection on key locations and types of litter to assist in future decisions on the best interception infrastructure