Before dawn, under a soft scattering of clouds, the Yarra River is still and silent. Most mornings the sight goes unappreciated by the majority of Melburnians – shared only by joggers, rowers and the early commuters who pass along the banks. The sky upriver is slow to warm, splashing orange and gold across the tallest city buildings until the day opens with a flash.
The banks of the Yarra are a major drawcard for residents and tourists alike. From the 1980s, extensive cleaning, replanting and developing have created a new urban precinct with admirably natural features. During the rest of the 20th Century, the river was notorious for the detritus of industry and the pollution of suburban runoff. Now, fresh beds of wetland plants line the river’s edge; swans, egrets and cormorants call and fly from the nearby refuges of Herring Island and the Botanic Gardens; rubbish traps collect the worst of the upstream spillage.
The thing is, these natural features aren’t very natural at all. The shaping of the Yarra – widening, straightening, grading – has led to a much more stable river course than what was originally present. Water from storms is filtered and driven into the bay along bluestone-lined banks. Upriver, dams and weirs keep the catchment rains and spring snowmelt in check as they tumble out of the mountains above the Yarra Valley. Nowadays, it takes the heaviest downpours to show unsuspecting people just how the landscape originally functioned.
A winter flooding in 2014 saw the river leave its banks behind and inundate waterfront businesses, saturating social media with images and stories. Cultural memory recalled a similar event, when the tributary creek sealed beneath Elizabeth Street spectacularly resurfaced in 1972 after heavy rains – perhaps the first time that many were given cause to consider the reason for the street’s low-lying topography.
Before European alteration, however, these events would not have been isolated quirks. The floodplain of the Yarra and Maribyrnong Rivers is home to an ecosystem that thrived on annual deluges, with the iconic river redgums (Eucalyptus camaldulensis) requiring spring floods to stay healthy. Each year, thawing snowfields would deliver a torrent of water through the Yarra Valley (its own floodplain now the location of fertile vineyards) down to Port Phillip Bay, recharging the soil and enriching those extensive wetlands of which Albert Park Lake is one final remnant. There is also evidence from other Australian sites that this cycle can prevent salinity from building up in the soil, having a direct impact on which plants could grow in the area and which animals could reside.
Floodplains rely on variability to maintain a patchwork of ecosystems, both temporally and spatially. Australia’s climate creates an especially changeable environment, with low rainfall leaving many parts of the region dry through the majority of the year. Their occasional submersion led to an eruption of germinating seeds and rapid new growth. Closer to the river, the more stable water supply allowed softer plants to grow and encouraged amphibians and birds. In contrast, the unchanging conditions of modern engineering favour some groups while stressing others, and can eventually lead to a loss of biodiversity.
Apart from the regulation of flow, other changes have affected the vegetation along the riverbanks as well. The slow-flowing surface of the river is undercut by a wedge of heavy salt water from Port Phillip, creating a saline gradient that runs well upriver. Unexpectedly, this common estuary pattern has only made a relatively recent appearance in the Yarra’s dynamic. It’s been that way since the 1880s, when a natural ford damming the Yarra downstream of Queen Street was blasted away to build the bridge that still stands.
Historically, the river was completely bifurcated by this rock formation, to the great advantage of the Wurundjeri tribe who took care of the land. Freshwater from upriver was retained en masse, ensuring a secure drinking supply that was kept separate from the saltwater of the bay. Eels and other fish were abundant in the region, along with birds arriving for the same purpose. The ford, and the waterfall it created, would also become a pivotal component in the decision of European settlers to start building; the deep, wide basin drummed into the riverbed below the falls was ideal to be used as a turning circle for cargo ships visiting the new city.
Changing the water from fresh to brackish meant that vegetation along the banks needed to cope with much higher amounts of salt, leading to community restructuring and a general reduction in quality. But while the upstream basin was significantly changed by saltwater mixing, it arguably couldn’t have been made much worse. Industries springing up in 19th Century Abbotsford and Collingwood, along with the suburbs encroaching along both banks, meant that an incredibly high level of sewage and commercial waste travelled directly into the river. At this point, the river was still being used as drinking water for the city, leading to chronic outbreaks of waterborne diseases. Continuous clean-up and revitalisation campaigns through the last century have improved matters, but the river still contains high levels of bacteria and heavy metals.
The unavoidable fact is that, like most metropolitan rivers in the 21st Century, the Yarra is at the mercy of the community around it. But it can also influence that community – as something so very visible in Melbourne, the river is uniquely positioned to remind us that our actions aren’t separate from the world around us. The new plantings along the riverbanks remind us that we can restore habitat if we try; the rubbish traps show us that waste removal doesn’t need to be complicated to work (as well as remind us to be more careful); the calling birds reward us by returning to the spaces we’ve made for them. As long as the river keeps flowing, it can be changed – one way or another.
Paul works in science education and has been a teaching member of Monash University's Department of Biology since 2010. He is interested in community engagement and sustainable urban development.
Banner image courtesy of Paul Jones.