Retarding Basins
Melbourne Water manages 209 retarding basins across Melbourne to help protect people and property from floods. While the main purpose of retarding basins is flood protection, some retarding basins include wetlands which treat stormwater before it flows into rivers, creeks and bays. Other retarding basins are incorporated into public areas, such as sporting grounds and parklands.
- What are retarding basins?
- How they work
- Why we need them
- Retarding basins as public open space
- Maintenance
- Where’s my nearest retarding basin?
Police Road retarding basin
What are retarding basins?
Retarding basins are urban holding ponds. They temporarily store stormwater runoff from a drainage catchment, helping to reduce the impact of floods on the stormwater drainage system, and protect properties located downstream by reducing flow rates for small to moderate flood events.
Retarding basins are of varying size and their capacity depends on the size of the catchment.
How they work
Retarding basins are designed to catch rushing water and slow it down, taking energy out of floodwaters. They release water gradually, like a bathtub with the plug out.
If a retarding basin reaches capacity, the overflow travels down a spillway to pass these higher flows from the retarding basin in a controlled and safe manner.
How retarding basins slow down and trap stormwater.
Why we need them
Retarding basins are critical in built-up areas to help reduce the impact of floods. Pavements, driveways and other structures create up to 35 times more runoff than rural areas, because the water is unable to soak into the ground.
Retarding basins:
- reduce the impact of floods on downstream development and waterways
- provide opportunities for councils and communities to utilise additional open space
- provide opportunities to introduce sediment traps and wetlands to improve water quality downstream
- can support areas of significant vegetation and wildlife.
Also see:
Retarding basins as public open space
Although the primary purpose of a retarding basin is for flood protection, we recognise that the community values these sites across Melbourne for their open space and wildlife values.
Many retarding basins are part of the Sites of Biodiversity Significance program aimed at protecting the environmental values of places that have plants and animals of state significance. Together we can look after these sites by:
- Observing warning signs
- Keeping dogs under control
- Picking up after dogs
- Taking any rubbish as you leave.
Please remember: Retarding basins can fill quickly after heavy rain. Always take note of weather conditions in the area before you visit a retarding basin.
Maintenance
Where Melbourne Water is responsible for the maintenance of the retarding basin, we cut grass, remove weeds and remove litter on a regular basis.
Our main priorities include making sure:
- plants and debris are not blocking drainage structures
- the site does not pose an undue fire risk
- weeds and pests are kept under control.
Some plants are left uncut because they play a vital role in filtering pollutants from stormwater as part of the treatment process.
At some highly urbanised sites, people may notice a temporary build-up of rubbish. This is typically litter washed by heavy rain from local roads and footpaths. This shows that the wetlands and stormwater quality treatment structures (such as litter traps) installed within the retarding basin are doing their job of preventing rubbish from entering our waterways and bays.
The litter is cleared on a regular basis, and we will also respond as soon as possible to reports of excess litter.
Troupes Creek West retarding basin, Narre Warren North
Where’s my nearest retarding basin?
There are 209 retarding basins across Melbourne and beyond, from Werribee in the west, north to Macedon Ranges and east to Bass Coast. Not all retarding basins are open to the public. Typically, retarding basins that are closed to the public are those that present an unacceptable risk to the public, such as rapid flooding during wet weather.
Find your nearest retarding basin:
Downloads
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