Stormwater is rain that runs off urban areas into drains that carry it into natural waterways such as rivers, creeks and the sea. Some of this flows to the ocean to maintain passage for our native fish.
Stormwater can contain many kinds of pollutants that it collects as it travels over land, including oil, grease, fertilisers, litter and heavy metals. Once stormwater enters waterways, these pollutants can adversely impact water quality and the ecosystems reliant on it. Some pollutants poison the fish, animals, insects and plants that live in and rely on these waterways. Other pollutants, such as nutrients, are present in such great quantities that they cause the excessive growth of unwanted plants that impact natural waterways and the marine environment.
Common pollutants found in stormwater include:
- oil, grease, fuel and metals from vehicles onto the road
- rubber from car tyres
- chemicals and paints that are not disposed of properly
- excess pesticides and fertilisers
- grass clippings and high loads of leaf litter in autumn from non-native trees are harmful due to high nitrogen content
The type and volume of stormwater pollution is influenced by:
- when it last rained
- intensity of the rain
- building density and other land uses in the catchment
- amount of vegetation cover
- the cleanliness of the streets
- local practices such as street sweeping, pet control and excessive garden watering.