Why manage stormwater
Stormwater needs to be managed as it can have an impact on our urban waterways. For new developments, it is essential that the right controls are put in place to manage stormwater, prevent flooding and improve water quality.
The characteristics of stormwater
In forested areas, the water balance or natural hydrology is altered only by rainfall and associated fluctuations in infiltration, evaporation and transpiration from plant growth. But in urban areas this natural hydrology is heavily modified, because land has been cleared of vegetation and capped with ‘hard’ or impervious surfaces.
When it rains, most rainfall runs off impervious surfaces such as roofs and roads and is typically transported directly and quickly to waterways through a drainage system. As a result, stormwater reaches waterways more often, more quickly and in greater volumes than waterways are naturally adapted to as there are limited opportunities for infiltration, evaporation and transpiration via plants in the landscape.
How does stormwater impact our waterways?
This change in the water balance and timing of flows, including sudden surges in water volume and velocity, impact on our waterways and bays. Some of the effects may be to:
- change the structure, variety and suitability of habitat for aquatic life such as fish and macro invertebrates
- disturb animals and plants that live in the waterway, and affect animal breeding habits
- erode stream banks
- alter natural flooding regimes
- increase turbidity and pollution, affecting water quality
- increase volumes of trash and oils
Overall these changes can reduce our ability to use waterways and significantly threaten animals in waterways such as birds and marine life such as dolphins and fish.
When new developments are planned, infrastructure and development controls are needed to manage stormwater and prevent flooding of properties.
Treating, using and retaining stormwater in the catchment can reduce the amount of stormwater reaching waterways and help reduce the frequency and severity of flooding. This is all part of a Water Sensitive Urban Design (WSUD), Sustainable Urban Drainage System (SUDS) approach to stormwater management.