Improving Melbourne's Drainage System
Melbourne Water is responsible for managing Melbourne's main drainage system - more than 1200 kilometres of drains. We work closely with local councils, which have responsibility for the suburban drainage system, including roadside gutters and smaller drains.
The drainage system carries rainwater from roofs, roads and buildings through gutters, drains and channels, and discharges it into rivers and creeks where it eventually flows to the bays.
Melbourne Water has a program in place to regularly monitor the condition of the drainage system to ensure it remains in good condition.
We invest about $19 million a year on inspections, maintenance and upgrade projects, which are prioritised following surveys and inspections. Since 1999/2000, Melbourne Water has invested $21.5 million on drainage upgrade projects.
Storms and flooding occur naturally, as does drought. Following a storm that has resulted in flooding, Melbourne Water inspects the drainage system to determine what impact it may have had on the system and whether the drains functioned properly.
It is important to keep the drainage system clear of litter and debris to avoid blocked drains that can cause flooding. This is also necessary to protect and improve the health of Melbourne's rivers, creeks and bays.
Today, new developments and redevelopments incorporate stormwater management measures that provide greater flood protection. About 150 areas known as retarding basins are used to help prevent flooding around Melbourne. They slow the flow of stormwater being carried in the drainage system by storing it for a period of time.
Retarding basins often double as parks and playing fields.
Improving water quality
In addition to providing flood protection, retarding basins can also improve water quality by incorporating:
- Sedimentation ponds, which promote settling of suspended sediment, preventing it from being washed downstream.
- Litter traps, which can be in a natural form such as reed beds, or engineered structures similar to pool safety fences, positioned to catch debris. They are usually placed upstream of sedimentation ponds and are designed to make litter collection as easy as possible.
- Wetlands which have been increasingly built in recent years within retarding basins to intercept nutrients and other pollutants in run-off from both urban and rural catchments. Wetlands are also an attractive landscape feature and provide a habitat for native wildlife.
An example of a wetland within a retarding basin is the Hallam Valley Retarding Basin Wetland at Hampton Park (Melway 95K3). This 16-hectare wetland is the largest purpose-built water quality treatment wetland in Victoria.