But with growth came a challenge: water. The land was prone to flooding, and repeated flooding was inevitable. Learning from the past, it was clear that traditional drainage systems simply couldn’t keep up.
The Dandenong Valley Authority:
a visionary beginning
In 1963, the Victorian Government established the Dandenong Valley Authority. This was a visionary, catchment-based statutory authority tasked with planning new urban development around water – not fighting against it.
Its mandate at the time was bold:
- Control flooding through purpose-built waterways, retarding basins and drainage channels.
- Protect new suburbs by reserving open space and land for storing and moving floodwater through the catchment.
- Fund drainage and flood infrastructure not through ratepayers, but through developer contributions – the beginning of modern drainage schemes as we know them today.
Across these newly developed suburbs, kilometres of green corridors were created and large, engineered drainage systems were built, such as the Hallam Valley retarding basin and contour drain and the Police Road retarding basin. These were not just drains: they were engineered floodplains, designed to perform the ancient role of the swamps they replaced while keeping new homes safe.
A turning point: the floods of
the 1970s
Then came the floods. Between 1973 and 1975, Melbourne was hit hard. Streets turned to rivers, homes were inundated and the cracks in the city’s flood management became impossible to ignore.
In response, the Victorian Government introduced the Drainage of Land Act in 1975. This landmark legislation shifted flood management from local councils to state authorities.
It gave agencies the power to:
- identify flood-prone land
- strengthen building regulations
- require new subdivisions to include drainage systems designed to cater for a 100-year storm event.
Before this, most drainage systems were only built to handle a 5-year storm. This change was dramatic but necessary.
In 1978, the principles of this new approach were formalised in the handbook Floodplain Management in Victoria. A decade later, the Water Act 1989 replaced the Drainage of Land Act, cementing the standards that still guide development today.
However, councils and authorities were not statutorily obliged to upgrade any existing drainage systems built before the late 1970s to the new standard.
Carrying the vision forward:
Melbourne Water
Today, Melbourne Water continues the work started by Dandenong Valley Authority, managing more than 200 drainage schemes across the city.
Over the last 50 years, each new suburb – from Werribee to Cranbourne, Mickleham to Pakenham – has been guided by catchment-based drainage strategies. These:
- ensure new development does not worsen flooding downstream
- set aside land for waterways and wetlands before house construction begins
- fund new drainage infrastructure through developer contributions, meaning communities are not left to pay the price and water bills can remain low.
In effect, modern Melbourne has re-learned what its swamps and floodplains have always taught: water needs space. As climate change brings new challenges, the importance of those early flood management decisions has never been more important. Because when the rain falls hard and fast, Melbourne’s forgotten swamps and waterways do not stay forgotten for long.
A city still learning
Despite this work, a number of challenges still remain:
- Increasing high-density development has reduced the area of porous surfaces that soak up stormwater, and the number of above-ground pathways for stormwater to flow into the drainage system.
- Some urban development has occurred without full knowledge of the location of flood risk areas.
- Flood mitigation work, such as increasing drainage capacity or building retarding basins, is becoming too difficult and expensive because of existing urban development.
In addition, climate change, further urban development and ageing drainage assets are likely to increase flood risks. Agencies thus face the dual challenge of controlling new risks while effectively mitigating the risks arising from drainage systems built to the old standard.
