Stormwater is the water draining off a site from the rain that falls on the roof and land, and everything it carries with it. The soil, organic matter, litter, fertilisers from gardens and oil residues from driveways it carries can pollute downstream waterways.
Rainwater refers only to the rain that falls on the roof, which is usually cleaner. However, stormwater can be a valuable resource. Reusing stormwater can save potable water and reduce downstream environmental impacts.
In urban areas stormwater is generated by rain runoff from roofs, roads, driveways, footpaths and other impervious or hard surfaces. In Australia the stormwater system is separate from the sewer system. Unlike sewage, stormwater is generally not treated before being discharged to waterways and the sea.
Poorly managed stormwater can cause problems on and off site through erosion and the transportation of nutrients, chemical pollutants, litter and sediments to waterways. Well-managed stormwater can replace imported water for uses where high quality water is not required, such as garden watering.
A homeowner can take simple steps to manage stormwater and reduce its environmental impact.
Take some simple steps to better manage stormwater and reduce the environmental impact of your home.
- Avoid cut and fill on your block when preparing the building foundations. Attempt to maintain the existing topography and drainage pattern.
- Retain vegetation, particularly deep-rooted trees. They lower the watertable, bind the soil, filter nutrients, decrease runoff velocities, capture sediment and reduce the potential for dryland salinity.
- Reduce erosion potential on site during building works by minimising the time that land is left in an exposed, unstable condition. Employ sediment traps and divert ‘clean’ stormwater around the disturbed site (see Sediment control).
- Minimise the area of impervious surfaces such as paved areas, roofs and concrete driveways.
- Grade impervious surfaces, such as driveways, during construction to drain to vegetated areas.