Note that even with the application of these principles, WSD is not a universal solution for land use change, and some sites or receiving environments may be considered too sensitive and/or their existing values too significant to allow development.
Promote inter-disciplinary planning and design
A project team should consider WSD principles as early as possible in the planning and design process.
A WSD approach requires the input and skill of a range of disciplines such as engineering, landscape architecture, urban design, community engagement specialists, planning and ecology, and is normal best practice in this regard.
By undertaking a design that is inclusive of a range of disciplinary fields, a project team can identify project risks and opportunities early in the design process, and can deliver multiple and complementary environmental, economic and social benefits from stormwater management.
Protect and enhance the values and functions of natural ecosystems
WSD aims to protect existing natural systems such as mature vegetation, aquifers, watercourses and wetlands for their stormwater management function. WSD also seeks to protect and enhance the beneficial properties of existing soils and subsoils, such as organic content and permeability.
The best means to protect natural systems and processes is through clustering land development on the most appropriate development sites in a catchment, limiting land disturbance and earthworks, and ensuring a balance of protected, enhanced and resilient ecosystem services.
Address stormwater effects as close to source as possible
WSD aims to limit impervious surfaces, such as roading and building footprints, that generate stormwater runoff. This may be achieved through intensifying or clustering development in appropriate areas of a catchment and/or through site-specific planning and design responses.
A WSD approach can also reduce ‘effective’ imperviousness by directing stormwater runoff to pervious mitigation areas in order to retain/detain and treat stormwater prior to entering reticulated networks or the receiving environment. This alleviates the potential downstream environmental effects from stormwater volumes, peak flows and contaminants. It also reduces the requirements for lower catchment stormwater infrastructure to manage these effects.
Mimic natural systems and processes for stormwater management
Natural systems, such as forests and streams, retain, infiltrate and transpire stormwater runoff and capture and transform contaminants. Treatment of contaminants occurs at the interface of soil, water and plant systems, including physical (e.g. filtration), biological (e.g. microbial action), and chemical (e.g. cation exchange) processes.
WSD promotes the restoration of natural systems and processes and their associated ecosystem services as part of catchment development. This includes the integration of these processes into engineered devices, such as treatment wetlands, swales, living roofs, raingardens and tree pits.