When it rains, stormwater flows over roads, car parks, sports grounds and other surfaces.
This water picks up litter, sediment, fertiliser and other pollutants that can harm wildlife and pollute our waterways. In 2011/12, a 'rain garden' was designed to collect and treat stormwater from the University of Tasmania Student Union car park and surrounding areas using Water Senstitive Urban Design (WSUD) principles.
Stormwater is diverted through a series of channels and vegetated basins where it is filtered through sandy soils and gravel.
Plants and soil microorganisms provide additional treatment, and the clean water is then released to the Derwent. Native plants and pools of water provide habitat for birds, insects and other wildlife, as well as an attractive green space that requires little maintenance. This project is an initiative of the Derwent Estuary Program and University of Tasmania, with funding from the Australian Government's Caring for Our Country.
The University of Tasmania has used WSUD design in other areas, including the Stanley Burbury theatre car park which all contributes to keeping pollution from reaching the Derwent estuary.
At a WSUD site near Cornelian Bay and the Brooker Highway it was found that pollution levels in stormwater such as heavy metals and hydrocarbons were reduced by up to 90 per cent. The plants and filtering system removed the majority of contaminants that entered the system.
Water sensitive urban design is increasingly being used in our cities to manage urban stormwater as a resource and/or protect waterways from stormwater pollution. Specifically it involves the use of infrastructure, landscape design or garden features to improve stormwater quality and reduce the impact of flooding.
The benefits of Water Sensitive Urban Design (WSUD) include;
- protecting the water quality of surface and ground waters,
- maintaining the natural hydrologic behaviour of catchments,
- protecting natural features and ecological processes,
- minimising demand on potable water supply systems e.g. through the installation of rain water tanks for gardens,
- integrating water into the landscape (e.g. wetlands) to enhance visual and ecological values,
- collecting treating and/or reusing runoff, including roof water and other stormwater,
- reusing treated effluent to reduce wastewater generation, and
- creating attractive green space and landscaping in urban areas.
For further information about using Water Sensitive Urban Design at home or at work see the DEP website.
The Derwent Estuary Program is a regional partnership between the Tasmanian State Government, councils, businesses, scientists and community-based groups to restore and promote the Derwent estuary.