A major tributary of the Yarra River, Merri Creek flows more than 60 km along the eastern edge of the Western Basalt Plains, from the foothills of the Great Dividing Range north of Wallan, to meet the Yarra at Abbotsford near Dights Falls. The rural upper and middle sections flow through the townships of Wallan, Beveridge and Kalkallo, while the middle sections through Craigieburn, Somerton, Epping, Lalor and Thomastown have become more enclosed by Melbourne's northern suburban growth.
Merri Creek is geologically younger than its neighbour the Moonee Ponds Creek. In a fairly shallow valley, its soils have provided fertile grounds for market gardens, public parks, plant nurseries and private gardens, as well as the more recent CERES environmental park in Brunswick. The Northcote Public Golf Links is situated on the creek's floodplain. Even in the earliest years of foundation and early Melbourne, the creek was subject to erratic flows, sometimes no more than a desultory dribble, at other times a raging torrent. Major flooding occurred periodically, with many notable inundations including those of 1872, 1891 and 1974. A Baptist Aboriginal School was located by the creek in Northcote from 1845 to 1851. A new road crossed Merri Creek in 1853, and Melbourne's oldest surviving stone bridges span the creek at Newlands and Murray Roads (Coburg) and Heidelberg Road (between Northcote and Fairfield).
The sides of Merri Creek are in places covered with 'trap' or columnar basalt (the creek's name derives from an Aboriginal word for rocky or stony), much of it quarried for construction of Melbourne's basements, rights-of-way and Pentridge Prison. From the late 19th century the creek was a popular spot for Field Naturalists' Club of Victoria excursions.
In the 1850s two young English brothers Henry and William Edwards farmed a property named Merrivale, around 14 km north of Melbourne in present-day Coburg. Henry was an amateur naturalist and collector, and recorded extensive descriptions of the flora and fauna of the Merri Creek vicinity. The surrounding land was already mostly cleared and under cultivation, many trees had been cut down for firewood, and species such as the kangaroo were fast disappearing. Edwards' commentary of the destruction of native fauna reveals the battle between the farmer and natural predators. The 'Native Cat' and falcons were terrible pests to poultry; from October 1853 to February 1854 nearly a hundred of the birds were killed just on the Edwards farm. The entomological section of the letter was published in The Edinburgh New Philosophical Journal in 1857. Edwards' account reveals the rapid and brutal transformation of animal and plant communities as a consequence of settlement and urbanisation: the Sulphur Crested Cockatoo once made its appearance around May in immense flocks numbering up to 500; 80 green tree frogs could be observed in the space of a few square yards; 200 Longicorne beetles were taken on a single tree in one morning. Forty years later in 1896, H.M.R. Rupp compiled a list of plants of the North Coburg/Campbellfield area, and it has been noted that 60% of his recorded species are not to be found in current surveys.
By the 1970s much of the natural environment of the Merri Creek valley was degraded. The Merri Creek Coordinating Committee was formed in 1976 as an alliance of community groups and municipal authorities to address planning and environmental concerns, while community action group Friends of Merri Creek (Inc.) has been active since the late 1980s in litter clean-ups, walks and tours, community education, water quality testing, and campaigning against a freeway and other threats to the creek.
The Merri Creek corridor contains significant natural, cultural and Aboriginal heritage. Major areas of extant native grasslands survive, for example, at Jukes Road (Fawkner), Central Creek (Reservoir), Galada Tamboore and Barry Road (Campbellfield/Thomastown). They contain endangered populations of native flora and provide crucial habitats for endangered reptiles and frogs. Archaeological sites along the creek contain artefact scatters of significance to the Wurundjeri, while two sites at Craigieburn were pastoral outstations for John Batman.