Stormwater quality

View of Quarries ParkStormwater is a term used to describe all the rainwater runoff in urban areas. Improving the quality of stormwater is important for the health of our waterways and seas.

Towns and cities contain large areas of paved or sealed surfaces such as roofs, carparks, streets, driveways and footpaths. Runoff from these areas flows into gutters, then into drains, and eventually out into the closest waterway. As the water flows over these surfaces, it picks up and transports litter, fuel, oil, fertilisers, herbicides, pesticides, fallen leaves, grass clippings, animal faeces, and sediment.

Stormwater is not cleaned or treated in any way. A few drains have litter traps installed, but most of the time the water and everything it picks up flows directly into waterways, such as the Yarra River and out to sea. Find out more about stormwater drains.

The Importance of Stormwater Management

Managing stormwater to keep it free of litter and pollutants protects the wide range of plants and animals in our waterways and ocean environments.

This is also important from a human perspective - clean creeks, rivers and beaches benefit everyone. Litter and toxic bacteria or chemicals pose risks to human health, and their presence in waterways and the sea restricts our ability to enjoy and use those areas. Reducing the load of litter and pollutants in stormwater is a difficult task, because there is not one specific source of pollution. Litter and pollutants come from everywhere, and keeping them out of stormwater requires a broad, community-wide approach.

The stormwater system has to be able to cope with very high quantities of water, to avoid flooding the streets during high rainfall events. Having adequate drainage ensures public safety and protects infrastructure from damage.

Some Ways to Prevent Stormwater Pollution

Stormwater pollution is everyone's responsibility, because we all contribute to it - either directly or indirectly.

Here are some simple steps to take which will help to reduce and prevent stormwater pollution:

  • Wash your car on the lawn or at a commercial car wash facility. Do not wash it in your driveway or on the street - the detergent will go straight into the stormwater drain. Washing on the lawn achieves two things at once - your car gets cleaned, and the lawn gets watered too! Some commercial car washes recycle and re-use their water, which reduces water consumption as well as protecting stormwater.
  • Put litter in the right place, and make sure it is secure and won't be blown around. Don't just pick up the paper and plastic - get the leaves, grass clippings, and animal faeces as well.
  • When working with chemicals and other substances (eg. changing your car oil, or spraying in the garden), make sure nothing can get washed into the gutter. Dispose of unwanted chemicals correctly, at facilities which are equipped for that purpose.
  • When working on garden projects, minimise the amount of soil left exposed or protect it from wind and rain with a tarpaulin. Keep stockpiles of topsoil or sand away from gutters, and cover them with a tarpaulin also.
  • Tell others about how their activities impact on stormwater and the wider environment. Help them to understand how they can protect stormwater too.
  • Refer to Yarra's Builder's Code of Practice for information on how to prevent stormwater contamination on building sites.

Stormwater Issues


  • Any litter lying around in the streets will eventually find its way into the stormwater system. About 2 billion litter items are washed into the stormwater system in Melbourne every year (Melbourne Water, July 2001). Litter harms native wildlife such as platypus, is ugly to look at, and is very expensive to clean up.

Organic Matter

  • Plant material - leaves, grass clippings and food waste are often considered 'natural' and therefore not a problem in waterways. In fact, these can cause significant water quality problems. As plant materials break down, nutrients are released into the waterways, creating ideal conditions for algal growth which can be toxic. Stormwater can also contain high numbers of weed seeds, spreading weeds far and wide and causing harm to the environment.
  • Animal waste - Animal faeces contain bacteria and nutrients which contribute to poor water quality - including high E. coli levels at swimming beaches, making it unsafe to swim.


  • These are mostly unseen. Fertilisers, herbicides and pesticides, fuel and oil, detergents, and others can all find their way into stormwater. These substances can have quite a damaging impact on the plants and animals in waterways, by changing the chemical composition of the water.


  • Water flowing over bare earth will pick up and transport soil particles into drains and then into waterways. This is a problem for several reasons. Sediment in water causes a muddy appearance, and reduces the amount of light which penetrates through the water. This in turn reduces growth of water plants, which reduces the amount of oxygen available in the water for aquatic animals. Secondly, large quantities of sediment can smother plants and animals on the bottom of waterways. Sediment build-up over time can block waterways almost completely. And finally, the soil particles themselves can carry other substances such as heavy metals, bacteria and nutrients.  

Further information

Kathleen Burke
Asset Drainage Engineer
9426 1599

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