Stormwater Facts and Solutions

In Cairns there are more than 260 drains and waterways whose water flows to the ocean. The water that is transported through these drains and waterways is called stormwater. It comes after rain lands on impervious surfaces like roofs, roads, and footpaths, makes it way into drains, creeks and rivers, and eventually flows into bays and the ocean.


Image courtesy of Tangaroa Blue –

Types of pollutants

Litter –  Plastic, plastic bags, cans, food wrappers

Litter is composed of man-made items that ended up in the marine environment through littering or dumping. Stormwater drains are able to carry items of litter out to the ocean, and if these are made of plastic they remain in the environment, for tens, hundreds or even thousands of years. Plastics waste in the ocean kills 100,000 marine animals and up to a million sea birds every year through choking, clogging, and entrapment. When plastics degrade into micro-plastics they are still harmful, as they contain carcinogenic toxins which get consumed by corals and filter feeders like whales, clams, and many fish.

On every beach around Australia you will find some form of marine debris, from rubbish swept down stormwater drains or left by visitors, to international debris that traveled thousands of kilometres onto our shores. The Australian Marine Debris Initiative (AMDI) is a national network of over 40,000 volunteers and partners, coordinated by Tangaroa Blue Foundation, focused on reducing the amount of marine debris washing into our oceans.

Sedimentation – Leaf litter, soils, garden clippings

Sedimentation is composed of the small organic particles that are washed down stormwater drains. These can come from a range of sources such as leaf litter and grass, eroded soil structures, and the weathering of infrastructure such as concrete paths, buildings and roads. When it reaches the ocean, sediment causes turbidity, or muddiness in the water and this can pose a number of threats to complex marine systems. Light is an important factor for the growth and survival of coral reefs. Small sediment particles have the ability to block the light coral needs to survive, to smother the coral and to even cause mechanical abrasions.

Nutrient rich pollutants – Fertilisers, animal faeces

Nutrients that stormwater drains introduces to the reef are typically in the form of fertilisers or animal faeces from pets and livestock. These are high in nitrogen and may also contain phosphorous, both of which cause a spike in population for algae. This is a problem because the algae use up all the oxygen and create “dead zones” in the ocean. They also block light, and clog up the gills of fish.

Drain Systems in Cairns

Cairns Stormwater System

In the central area of Cairns alone, there are 20,000m of culverts, 58,000m of open drains, 168,500 m of pipes and 3,800m of waterways. The drainage network is a combination of pits, pipes, open channels and natural waterways which is continually developed, managed and maintained. These carry stormwater into creeks, rivers and other catchments. The stormwater eventually ends up in the ocean. As stormwater is not treated, everyone has a role to play in keeping pollutants out of the stormwater system to ensure the long-term health of our rivers, creeks and oceans. Find out more here.

Cairns Wastewater Treatment

Unlike water in our drains, water we use in our toilets, taps, and showers gets treated before entering our natural environment. Cairns town water ends up at the Marlin Coast waste water treatment plant, which operates a bio-nutrient reduction system. Here, it is transformed from sewage, by an activated sludge process, into ‘A’ grade recycled water and a small amount of solid waste. The water is supplied to a local school and golf course for irrigation, and the remainder flows to Moon Creek and into the Coral Sea. Read more here.

Easy Ways You can Prevent Stormwater Pollution

In Your Home

When you are at home you can prevent pollution in drain water systems and do your bit for the ocean by taking a few easy actions.

Some of these are:

  • Recycle plastics, glass and paper/cardboard waste appropriately. More Info
  • Put other rubbish in bins. Take oils and large, non-recyclable items to a transfer station. More Info
  • Compost vegetable waste if possible – your garden will thank you for it. More Info
  • Use cleaning products that are environmentally friendly. More Info
  • Avoid products such as exfoliants that contain plastic micro-beads.

With permission from Steve GreenbergImage with permission from Steve Greenberg

In Your Garden

There are a number of actions you can take when you are outside your home that can prevent pollution being washed down your stormwater drains.

Some of these are:

  • Picking up after your pet, and placing the animal faeces into a rubbish bin, instead of letting it wash down the drain. More Info
  • Washing your car or boat on the grass instead of in the driveway and limiting your use of cleaning products. More Info
  • Fixing your car in the garage instead of on the street to prevent oil leaks onto the road.
  • Sweeping and collecting leaves and dirt from pathways rather than hosing them down the drain.
  • Keeping streets and gutters litter-free. Picking up any discarded litter and placing in the appropriate bin.
  • If possible, avoid using fertilisers, pesticides and herbicides. If you do need to use them, reduce the chance of run-off into the stormwater system by taking care not to use too much and do not apply them before rain is expected- you waste money and pollute the sea water.
  • Don’t pour excess paint down the drain. Let it dry and then put it in a rubbish bin. Wash paint brushes over grass, not down the drain.
In Your Community


There are a number of ways you can positively contribute to ocean health within your community.  The most important thing you can do is share your awareness with your family and friends. Talk to them about water quality, waste, litter and pollution, and how we can all do our bit to improve the water quality of our Great Barrier Reef.

Other things you can do are:

  • Take your own reusable bags when you go shopping
  • Get involved in a beach clean up. Find out more here
  • Carry your own water bottle. Do you really need to buy drinking water in plastic bottles anyway? Maybe you can just refill yours from a tap, and save yourself some money too!
  • When you buy food or a drink, think about how it is packaged. Can you make a better choice to avoid or minimise the use of packaging and containers? Maybe when buying coffee you can bring your own mug?

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