Stormwater is water that runs off surfaces into drains. It’s not the same as rainwater, which falls on roofs and is cleaner.
How stormwater gets contaminated
As stormwater drains, it carries pollutants with it like litter, sediment and oil. These are a major cause of pollution in our rivers, creeks, lakes and bays.
Most of the time it’s everyday activities that cause urban stormwater pollution, not major spills or industrial accidents. It’s important to prevent waste from our homes or businesses polluting stormwater drains.
Pollution of our waterways can be a result of many things, such as:
- industrial runoff from workshops
- people washing their vehicles in the street
- general litter – like plastic bags, bottles and cigarette butts.
Why stormwater pollution is a problem
Population increases are impacting the quality and quantity of stormwater that reaches our waterways.
Stormwater quality
The stormwater system takes rainwater from our streets and gutters into the closest waterway.
Unlike sewage, stormwater enters our waterways untreated. At the end of the pipe system there are options for treating stormwater. For example, with pollutant traps that remove large, non-biodegradable pollutants. But in most cases, it flows from our streets and gutters into our creeks, rivers and the ocean.
Stormwater quantity
An increase of built-up areas causes more stormwater runoff to enter our drains and waterways.
Stormwater drainage systems usually remove stormwater from urban areas as quickly as possible. This is to reduce the risk of flooding and prevent water stagnating. The increased volume entering waterways causes scouring (in-stream erosion) of waterways.
Read more about stormwater
Reviewed 6 March 2020
