Stormwater

When it rains in urban areas, water runs off hard surfaces like roofs, roads, car parks, paths and driveways into stormwater drains. 

Stormwater flows into small drains which lead to larger stormwater drains and eventually join large (trunk) drains or pipes that carry the water to creeks, rivers and the ocean.

Watch our video to find out more about Sydney's stormwater network.



 



 
Stormwater culvert

Stormwater drains are dangerous.

Stormwater drains can be very dangerous places. This is why stormwater drains are often fenced and have warning signs telling people to stay out
 
It's important that you don't go into drains - even during fine weather. It's also a good idea to keep pets away from drains.

Stormwater drains can be open channels or underground tunnels. They are dangerous because:

  • water in drains can rise quickly and unexpectedly, even when it's not raining in the local area
  • huge amounts of water can suddenly wash into the drain when it rains
  • you may not be able to get out of a stormwater drain if you're swept away by water - you could even drown
  • even shallow water can be very powerful and could knock you over
  • drains can contain pollution like broken glass, dangerous chemicals and disease-causing bacteria.


Don’t try to lift stormwater grates near footpaths and roads, even if something has accidentally dropped down. These grates can be very heavy.

If you're in a flooded area, stay away from roads, footpaths and areas where you can’t clearly see where you're walking.

What kinds of things are in stormwater?

Water is a solvent, which means it dissolves things. Wherever it travels, water carries chemicals, minerals and nutrients with it.

Stormwater carries all the things that collect on hard surfaces, like roads, footpaths, driveways and roofs.

Some examples of things in stormwater are:

  • litter, like plastic bottles, food packaging and cigarette butts that people leave on the street
  • oil and grease from cars
  • dirt, leaves and twigs
  • animal and bird droppings
  • chemicals, including nutrients, from washing the car on the driveway or road.


How is stormwater quality managed?

Unlike wastewater, stormwater isn't treated before flowing into creeks, rivers and oceans.

We (and many councils) manage stormwater using Stormwater Quality Improvement Devices (SQIDs).

SQIDs can include things like:

  • trash racks
  • sediment traps
  • litter booms
  • constructed wetlands.


SQIDs are designed to catch solids so they can be removed from the water.

In the past 20 years, we've installed 70 SQIDs. These devices have helped remove over 35,000 cubic metres of litter and organic waste as well as 39,000 tonnes of sediment from stormwater before it reaches Sydney’s natural waterways.

Learn more about what we're doing to manage stormwater.

 
A stormwater quality improvement device full of rubbish

Stormwater Quality Improvement Devices (SQIDs) collect rubbish from waterways.

What can you do to help?

Drain is for rain

Stormwater drains are just for rain!

You can help us keep our waterways clean by:

  • putting rubbish in the bin
  • washing cars on the grass instead of hard surfaces so detergents wash into the soil rather than stormwater drains
  • sweeping leaves, dirt and rubbish away from gutters
  • making sure your gardens have good borders so soil doesn’t wash away
  • putting grass clippings in the compost bin or on the garden
  • picking up your pet’s droppings and putting them in a bin
  • disposing of chemicals, pesticides, paints and oils using your local council's Household Chemical CleanOut services.

What is water sensitive urban design?

It's important to consider the water cycle as part of our built environment. When the water cycle is included in planning, designing and constructing our built environment it's called water sensitive urban design (WSUD).

Our built environment often includes hard surfaces, like roofs and roads, that interrupt the natural water cycle processes of run-off, infiltration and percolation. WSUD concentrates on making sure these processes can still happen.
 

Small creek flowing between trees with houses in the background

Water is an important part of our built environment.


When using WSUD we have to take lots of things into consideration, such as:

 

  • safety - will the design create dangers such as falling or downing?
  • maintenance - how and who will look after the area and maintain it after it's built?
  • water quality and quantity - what quality and how much water is flowing in? What quality is the receiving environment?
  • available space - how much land does the design take up? Are there existing habitat or land features that will be impacted?
  • climate - what rain patterns does this area receive? Will the design need to cope with high volume, infrequent rain events or low levels of rain over a long period of time?
  • landscape - what is the topography and slope of the land? What type of soil is in the area? Different soils have different percolation rates.
  • community - how will the area be used by community? What are the benefits and impacts on the community?

What are the features of water sensitive urban design?

There are many features that can be used individually or together to make a design more water sensitive. 

Features can change how the water flows through the environment and improve water quality.

Using the table below, decide which feature you would use for these scenarios:

A sediment basin

Sediment basins are designed to slow water down so sediments can settle.

  • Stormwater that has no fine sediments but lots of plastic drink bottles. 
  • Stormwater that runs off a large car park and carries lots of fine sediments.
Feature Description Good for
Vegetated swales Water flows through a wide, shallow channel made out of gravel and soil.

Plants growing in the channel slow the water down, encourage sediments to settle and capture litter and organic matter.
Removing litter, organic matter and fine sediments.
Sediment basins Water flows into a basin (pond) that encourages the water to slow down and sediments to settle. Removing litter, organic matter and fine sediments.
Constructed wetlands Water flows into a large man-made wetland that has design features that encourage settling, biological treatment and fine filtration.

Lots of plants are used to enhance the treatment and provide habitat for wildlife and fish.
Removing fine sediments, nutrients and heavy metals.
Gross pollutant trap A physical barrier that traps litter and large organic matter (leaves and twigs) as the water flows through.

Gross pollutant traps need to be cleaned and the rubbish taken away.
Removing litter and organic matter
Porous pavements Porous pavements allow water to infiltrate through a surface, rather than run-off it.

They can be used for footpaths, carparks and areas next to roads.
Removing fine sediments
A constructed wetland

Constructed wetlands are good at removing nutrients, sediments and heavy metals.


Collecting and treating stormwater so it can be recycled is called stormwater harvesting.

Stormwater harvesting can help reduce demand on drinking water supplies by providing another water source for things like:

  • watering sports fields and gardens
  • flushing toilets
  • washing machines (in some cases).

These activities don't require water to be treated to a drinking water standard.

Watch the   Video case studies - stormwater re-use projects to learn more.

Sprinkler spraying plants

Nurseries can use harvested stormwater instead of drinking water to water plants.


Finding practical and cost effective stormwater harvesting options is a challenge. Some of the problems are:

  • finding suitable space to build large storage and treatment facilities
  • treating the stormwater so it's good quality
  • finding efficient ways to re-use the water, including transporting the treated stormwater to where it's needed
  • making sure stormwater harvesting doesn't damage waterways by reducing natural flows.

Many schools have large areas of hard surfaces like car parks, basketball courts, assembly areas or concrete quadrangles. These hard surfaces increase the amount of stormwater run-off that goes down the drain.

By doing a stormwater audit, you can:

  • find your school’s stormwater drains
  • see how polluted the stormwater drains are
  • work out why the stormwater drains might be polluted
  • create a Stormwater Management Plan to reduce pollution in the drains.


By taking the actions identified in your stormwater audit, you can help reduce pollution in local waterways.

Download our Stormwater audit fact sheet to find out how to audit your school's stormwater drains.

A trash rack

You can help reduce pollution in water ways, like the rubbish collected in this trash rack.