Urban wetlands are now recognised as an important part of the landscaping of public spaces. Landscaping urban wetlands and surrounding areas can be a challenge for landscapers not least of which is controlling the runoff from the landscape work. For example, exposed aggregate concrete etching can create acid runoff which can pollute nearby wetlands, groundwater and streams. The landscaping contractor needs to be mindful of that and ensure runoffs are controlled or adequately diluted. One solution for this is to use sandbags to direct the water runoff from exposing concrete to where the next crossover is being constructed. This is not just eco landscaping, it is responsible landscaping.
Balwyn Community Centre Urban Wetlands redevelopment
For our recent landscaping project at Balwyn Community centre, the design by landscape architects, ACLA, included a few landscape design changes to the urban wetlands. These were aimed at improving the safety and amenity of the urban wetlands, whilst preserving their character and biodiversity. This type of landscape design is essential where there is a wetland close to a public space like Balwyn Community Centre.
Balwyn Urban Wetlands Landscape Construction
One of the major changes to the landscape involved reshaping the wetland with an excavator. The pool was made also made shallower and a rock beach using 70mm river pebble was added. This landscaping work required draining the wetland and letting it dry out enough to safely use the excavator. Draining a wetland like this requires a permit from the EPA to avoid any pollution problems in the stormwater system. For the safety of children using the Balwyn Community Centre playground, a childproof fence was constructed around the wetlands. Making the pool shallower with a pebble beach also improved the safety of the wetland.
The Yoga mat in the tranquil settings of Balwyn Community Centre Urban Wetlands
A fallen tree trunk becomes part of the urban wetlands project.
Late into the project a large eucalyptus tree fell onto the fence and destroyed part of it. As with native bushland, fallen tree trunks create habitat for insects and native fauna, so Boroondara City Council and the landscape architect, ACLA decided to keep the tree trunk inside the wetland.
Refilling of the refurbished wetlands was by natural runoff from the landscaped area.
A fallen tree truck becomes new habitat by the urban wetlands of Balwyn Community Centre
Why do we put this effort into preserving urban wetlands and Coastal wetlands?
Wetlands are some of the most productive ecosystems in the entire world, providing a range of benefits for both people and the environmental. Wetlands are defined as an area of land where the soil is covered by water for either all of the year, or only certain times of the year. They may be man-made or naturally forming and the water itself may be static or free flowing, fresh, brackish, or saline. Examples of wetlands include lakes, lagoons, billabongs, swaps, marshes, mudflats, mangroves, peatlands, and even coral reefs.
The conservation and restoration of these ecosystems is essential for protecting biodiversity, water quality, flora and fauna, and areas deemed to be of cultural significance. Below we explore these reasons in further details:
- Important Sites For Biodiversity
Wetlands are the most biologically-diverse of all ecosystems. Often referred to as ’biological super systems’ they produce large volumes of food that support a remarkable level of biodiversity. In relation to the number and variety of species supported, wetlands are as rich as rainforests and coral reefs. In fact, the International Union for Conservation of Nature estimated that 126,000 described species rely on freshwater habitats alone and 45% of all fish live in freshwater wetlands.
- Protect And Improve Water Quality
Maintaining and improving water quality is one of the most important benefits that wetlands can provide. Wetlands have the capacity to act as filtering systems, removing sediment, nutrients, and pollutants from water. They do this by slowing down water flows from upstream, reducing erosion, and preventing sediment from being transported downstream.
Soils and the vegetation in urban wetlands can capture, process and store both nutrients and contaminants. In addition to this, they can reduce harmful bacteria and pathogens in the water prior to it being returned to groundwater.
- Providing Habitats For Aquatic Animals
For many aquatic animals, inland wetlands are the only habitat in which they can survive. The wetlands provide all the food, water and shelter that aquatic animals require. Wetlands provide a safe habitat for feeding, spawning and nursery sites for native fish such as Freshwater Catfish, Blue-spot Gobi, and Long-finned Eel. Overall, healthy wetlands sustain healthy wildlife and fish populations as they contribute to large amounts of nutrients, ultimately resulting in better high-functioning ecosystems.
- Store Stormwater And Floodwaters
With the rise of urban development across major cities, the management of storm water is a cause of great concern. Excessive stormwaters and floodwaters caused by the increase in non-porous or impervious grounds can cause significant economic burden and damage to infrastructure. However, urban wetlands are nature’s detention basins, providing a space for floodwaters to be temporarily stored, retained long-term, or even returned to the water table. Urban wetlands that are in positions downstream in residential areas are valuable at controlling localised floods. The preservation and restoration of wetlands are a natural alternative to expensive dredge operations and levees.
- Maintain Surface Water Flow During Dry Periods
Water supply in wetlands is constantly changing; it can be filled by rainfall, or drained by groundwater. In Australia, water flows are highly variable both within and between years. Wetlands have the ability to reduce water flow velocity with densely populated water vegetation. Wetlands have a rich biodiversity of plants that have evolved to suit these varying conditions. This ensures that, during the drier months, the wetlands can maintain surface water flow to sustain the habitat for both the vegetation and animals.
- Protect Our Shores From Wave Action
Coastal wetlands, such as estuaries and marshes, are an integral part of shore protection schemes as they can provide suitable protection from wave action along with creating species diversification. Coastal wetlands provide a buffer zone that is biologically diverse, which ensures that the exposed shoreline vegetation is maintained. Erosion is also prevented by absorbing wave energy.
- Provide Habitat For Plants
Wetlands contain a wide diversity of life, supporting animals and plants that are often found nowhere else. In fact, in Australia thousands of plant species grow in wetlands, ranging from mosses and grasses to shrubs and trees. Wetland plant communities are often protected as they contain flora that is endangered under the Biodiversity Conservation Act 2016. Some common plants found in wetlands include lignum, the common reed, and river red gums.
- Provide Habitat For Animals
The biodiversity of animals in wetlands is also well documented. Huge numbers of birds, frogs, mammals and reptiles spend all or part of their life cycles in wetlands, which provide habitat and food sources for them to survive.
Common wetland birds include the Australasian Grebe, Pacific Black Duck, and Great Egret. In relation to frogs, the most common species found in wetlands are the Striped Marsh Frog, Brown-striped Grass Frog, Spotted Grass Frog, Green Tree Frog, and Red-eyed Green Tree Frog. Of the mammal species, the Swamp Rat, Platypus, Fishing Bat, Common Planigale, Common Blossom-Bat, Eastern Chestnut Mouse, and the Pale Field Rat all live within wetlands. Many different species of reptiles also thrive in wetland environments, including turtles, water skinks, and snakes.
A grebe in an Urban Wetland near Cranbourne. (Photo Shane Borham)
A Black fronted dotteral, a type of plover. enjoys the mud at this urban wetland near Cranbourne. (Photo Shane Borham)
- Are Culturally Significant
It is important to acknowledge that wetlands are also culturally significant to Aboriginal and Torres Strait Islander people. Wetlands have Aboriginal cultural and historical significance, and are important for science and education.
- Ability To Absorb Pollutants
Due to the nature of drainage within urban areas, stormwater is often directed to wetlands. This water is often polluted with sediment, microorganisms, phosphorous, and nitrogen. A healthy, biodiverse wetland has the ability to ‘absorb’ these pollutants. The wetlands can filter these pollutants, reducing the load through processes in aerobic and anaerobic ecological conditions.
- Wildlife Corridors
A wildlife corridor is any area of native vegetation that is located between two or more larger areas. It is a ’stepping stone’ for migrating animals to use in-between native landscapes. Wetland wildlife corridors provide this function for many waterbirds, allowing them to safely migrate while providing shelter and food. In addition to providing a refuge for migrating animals, wetland wildlife corridors also enable interbreeding and colonisation of plants native to the local area. Significant wildlife corridors close to Balwyn Community Centre include the anniversary bicycle path through Deepdene and East Kew as well as the chain of parks along the Yarra river. These parks include Burke Road Billabong Reserve and Hays Paddock in East Kew as well as Bellbird Park in Kew.
- Recreational Use
Many coastal and inland wetlands are popular for tourism and recreational activities such as swimming, hiking, boating, fishing, camping, and birdwatching. They are places of beauty that can be a great source of relaxation and recreation.
Early Spring in Melbourne and this black swan is raising cygnets in urban wetlands near Cranbourne. (Photo Shane Borham.)
A Chestnut teal swimming in wetlands near Cranbourne. (Photo Shane Borham)
- Recharging Groundwater
Wetlands recharge groundwater when they become so clogged with water that the soil can no longer retain it and the water leaks down into the aquifer. This is important as the process of leaching not only recharges the groundwater, but in doing so it also absorbs the bacterial loading of the excess water, ensuring that the groundwater is replenished with less contaminated water.
Landscaping with Urban Wetlands
A trend we are seeing is that landscape architects, local governments and developers are preserving and even adding wetlands to landscape redevelopments. Private developers are now creating wetlands and pools to provide a tranquil place for employees and visitors.
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References and further reading
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(2018a). Plants in wetlands. [online] NSW Environment, Energy and Science. Available at: https://www.environment.nsw.gov.au/topics/water/wetlands/plants-and-animals-in-wetlands/plants [Accessed 1 Sep. 2020].
(2018c). Why wetlands are important. [online] NSW Environment, Energy and Science. Available at: https://www.environment.nsw.gov.au/topics/water/wetlands/why-wetlands-are-important [Accessed 1 Sep. 2020].
(2019). Plants and animals in wetlands. [online] NSW Environment, Energy and Science. Available at: https://www.environment.nsw.gov.au/topics/water/wetlands/plants-and-animals-in-wetlands [Accessed 1 Sep. 2020].
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Department of Agriculture, Water and the Environment. (2016b). Department of Agriculture, Water and the Environment. [online] Available at: https://www.environment.gov.au/water/wetlands/publications/factsheet-wetlands-water-changes [Accessed 1 Sep. 2020].
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Healthy wetlands, healthy fi sh populations What are wetlands? (n.d.). [online] Available at: https://www.mdba.gov.au/sites/default/files/archived/mdbc-NFS-reports/2200_factsheet_Fish_and_wetlands.pdf [Accessed 1 Sep. 2020].
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Water Sensitive Urban Design. City of Boroondara