Water Sensitive Urban Design

Bioretention systems are vegetated soil media filters, which treat stormwater by allowing it to pond on the vegetated surface, then slowly infiltrate through the soil media. Treated water is captured at the base of the system and discharged via outlet pipes.

Raingardens are one type of design used to treat stormwater runoff. They are small bioretention systems build on residential and industrial lots.

Swales are channels with gently sloping sides. They can be lined with grass or a variety of dense vegetation. Swales convey stormwater while screening and removing pollutants.

Rainwater tanks are used to collect rainwater runoff from roof areas. Rainwater tanks reduce harm done to natural waterways by reducing the volume of water entering the waterways and reusing it. Rainwater tanks can be used for flushing toilets, washing clothes, and irrigating gardens.

Gross pollutant traps (GPTs) capture litter, sediment and debris that is washed into the stormwater system. They prevent pollution from entering the rivers and streams. GPTs are mostly proprietary products that come in a variety of size, functions and maintenance requirements.

Filter cartridges are proprietary products that are designed to filter fine pollution, such as nitrogen, phosphorus, fine solids, oil, and other nutrients.
They may require pretreatment such as a GPT upstream and are located underground in filter chambers.

Constructed wetlands are engineered ponds that form a series of shallow, densely planted areas that help filter water through physical and biological processes. They provide a natural way to treat and remove pollutants from stormwater.

Permeable pavements are porous surfaces which overlay an aggregate layer of crushed stone or gravel. Stormwater runoff passes through the permeable pavement to the aggregate layer before it is discharged to a piped drainage system. This process reduces the peak flow site runoff by delaying time for water to enter drainage system and improves the quality of stormwater runoff by removing site pollutants.

When rain falls on vegetated areas such as bushland it is filtered by soil and plants, and soaks back into the ground. When rain falls on hard surfaces such as rooftops and roads it cannot soak into the ground and becomes stormwater runoff. Stormwater runoff picks up pollution such as dirt, chemicals and litter, carrying them into stormwater drains and into waterways. These pollutants contains nutrients that can cause algal growth.

Bioretention basins are designed to remove a wide range of pollutants from stormwater runoff. When stormwater is redirected into the bioretention basin it ponds temporarily before being slowly filtered by native plants. As the stormwater seeps through the layers of soils, sand and gravel, the plants absorb nutrients like nitrogen and phosphorus. Fine sediments and other pollutants are also captured. Bioretention basins also reduce the amount of stormwater that would otherwise wash pollutants into river and creeks.

No. Water will only pond for a few hours after rain. Using the correct soils and plants will allow it to filter and drain away quickly.

No. The basins drain within a few hours of most storms. Any mosquito eggs will die before they have a chance to hatch.

Yes. Basins include a mixture of trees, shrubs and grasses that provide habitat and food for a variety of birds, frogs and mammals