‘Hard’ stormwater infrastructure, such as pipes and concrete channels, is a means to convey stormwater runoff in order to manage flood risk to property and people.
However these structural elements are often a source of adverse effects on the environment, by rapidly concentrating stormwater flows and their contaminants to the receiving environment. Their effectiveness is also limited by system capacity (e.g. pipe diameter).
WSD approaches focus on reducing or eliminating stormwater runoff generation through source control, and utilising natural systems and processes to manage stormwater quantity and quality effects. WSD is inherently a context-specific approach which utilises a combination of conventional stormwater infrastructure, WSD devices (e.g. swales and raingardens), and enhanced natural systems to achieve the best practical stormwater management outcome. This includes the potential to utilise stormwater as a supply for potable water or irrigation.
WSD is a design approach based on a set of guiding principles. WSD is therefore applied as ‘best fit’ for the planning or design context. In a greenfield situation, especially where there are valuable and sensitive environments, the benefits of protecting natural resources are significant. In a brownfield or redevelopment scenario, there may be significant existing built constraints, fixed costs (i.e. existing assets), and limited existing natural resources. However, this does not limit the potential for the principles of WSD to be realised through innovation and appropriate site design. This may include working with the configuration or height of buildings to provide the greatest development yield for their footprint, the retrofit of living roofs, living walls and pervious paving, or integrating vegetation into the redeveloped site to enhance ecosystem services.