Two of the four principles of WSD refer to natural systems, namely 'Protect and enhance the values and functions of natural ecosystems'; and 'Mimic natural systems and processes for stormwater management'.
An environmental framework such as that in Figure 15 determines the value of existing on-site environmental resources at the regional, catchment and site scale. Site layout is then optimised to protect and enhance on-site resources. An environmental framework is built from the data collected during the Site Assessment phase.
An environmental framework is a means to ensure that sufficient ecosystem services are provided in a site or catchment to support the wellbeing of communities in current or future developments. It ensures the principles of WSD are considered by protecting and enhancing a site's natural systems across open space networks, ecological corridors, receiving environments and enhanced landscapes. A project team will generally consider the following site elements or attributes as part of a combined environmental framework:
- Landscape and natural character values
- Soil and riparian ecosystems
- Biodiversity values to ensure native species resilience
- Ecosystem connectivity to ensure ecosystem resilience.
To assist with the determination of values, Auckland Council has produced several documents which provide guidance for developing an environmental framework. These are:
- TR2009/083 Landscape and Ecology Values within Stormwater Management (Lewis et al., 2010)
- Criteria for the Identification of Significant Ecological Areas in Auckland (Sawyer & Stanley, 2012).
Environmental frameworks are prepared by ecological and landscape specialists to ensure the classification and optimisation of on-site resources is completed correctly. Getting these specialists involved early on in the Site Analysis phase provides the best opportunity to maintain and enhance the environmental resources of a site.