In order to balance development with supporting ecosystem services, it is necessary to promote WSD outcomes at the complementary planning scales of the 'region' (in this case the Auckland region), the 'catchment' (or community), and the 'site' (or neighbourhood) scale (Figure 14).
The application of WSD principles at these planning scales is introduced below, and discussed in more detail throughout Section D.
Regional scale
The Royal Commission Findings on Auckland Governance (Salmon et al., 2009) called for robust, considered and consistent planning to support the region's ongoing growth and development. At the regional scale, WSD contributes to this process by promoting resilient ecosystem services to support an appropriate growth pattern.
The promotion of WSD principles at the regional scale is based on a clear understanding of the values and connectivity of ecosystem services in the region. It is also a means to promote the collaboration of stakeholders with regulators in planning processes. The WSD principles previously introduced in Section A of this guideline are presented below in consideration of the regional scale.
- Promote inter-disciplinary planning and design. Collaboration between Council units and developers can lead to opportunities for integrated objectives and priorities for infrastructure (environmental, social, property and transport).
- Protect and enhance the values and functions of natural ecosystems. Provide for the protection of representative and rare natural systems in regenerative patterns in order to achieve ecological connectivity and resilient ecosystem services in the region. Water quality requirements are often driven by the goal of protecting regionally significant ecosystems.
- Address stormwater effects as close to source as possible. Cumulative effects become significant at the regional scale. Mitigating the effects of development on the environment is difficult and costly with an "ambulance at the bottom of the cliff" approach. Mitigating issues as close to source as possible avoids these cumulative effects and provides resilient mitigation systems through the removal of central points of failure.
- Mimic natural systems and processes for stormwater management. Increase the resilience of natural systems and processes for stormwater management across the region by promoting appropriate development patterns for headwaters and aquifers, watercourses, inland lakes, isolated wetlands, and coastal areas. Look to broad regional ecosystem enhancement opportunities such as urban forestry, a system of natural floodplains, or creating large scale wetlands.
Catchment scale
The catchment is the most useful spatial planning scale for the implementation of WSD principles. There is a direct causal link between stormwater runoff within a catchment boundary, and potential downstream effects to receiving environments. Catchments are defined by topographic boundaries, which also form discrete land management units and inform the potential layout and intensity of the built environment. Catchment planning requires an understanding of three interrelated processes in the catchment:
- Land use practices generating stormwater runoff and contaminants
- The means in the catchment (natural or structural) to detain, retain, treat, convey and attenuate stormwater runoff
- The values, natural functions and intended uses of receiving environments.
The best means to apply WSD principles at the catchment scale is through the integration of parallel planning processes such as catchment management plans (CMPs), watercourse management plans (WMPs), sustainable catchment programme (SCP) plans and comprehensive development plans (CDPs). These plans can focus on converging infrastructure issues in the catchment to ensure a balance of built and natural environments, and to reflect the values and sensitivities of the receiving environment. The WSD principles previously introduced in Section A of this guideline are presented below in consideration of the catchment scale.
- Promote inter-disciplinary planning and design WSD promotes early consultation between individuals in the Council and the development community. A working group within the Council, potentially including large landowners, can share information and mutually agree objectives and priorities for a catchment. This is a means to ensure infrastructure planning achieves multiple objectives across stormwater management, ecology, urban design and cultural values. This also provides an opportunity to combine engagement with community, iwi and public agencies on a range of issues.
- Protect and enhance the values and functions of natural ecosystems. Natural ecosystems, including vulnerable soils, groundwater aquifers, areas of terrestrial vegetation, wetlands and surface watercourses can be assessed at the catchment scale to ensure they operate as connected and therefore resilient natural systems. This includes retaining and enhancing ecological connections with adjacent catchments for broader regional landscape linkages. Natural systems can be further enhanced in areas of the catchment if they are to specifically moderate the impacts of built environments.
- Address stormwater effects as close to source as possible. WSD promotes the location of land uses based on the capability of directly affected environments. Where increased stormwater runoff is likely, a treatment train can be applied as a combination of landscape areas, swales, raingardens, restored streams, etc. acting in a sequence from the source to the receiving environment.
- Mimic natural systems and processes for stormwater management. At the catchment scale, natural systems and processes can be complemented with interventions such as raingardens, remediated soils and revegetation in upper catchment areas; restored streams, wetlands and swales attenuating flows in mid catchment areas; and broad natural floodplains and enhanced receiving environments in the lower catchment.
Site scale
The site scale is usually the most relevant to land developers. It is informed by regional and catchment planning as discussed above, but there is also a more detailed assessment which informs planning and design outcomes. The site planning process is covered in detail in Section D5.3, and is summarised below in terms of the WSD principles previously introduced in Section A of this guideline.
- Promote inter-disciplinary planning and design. An inter-disciplinary team provides a comprehensive assessment of a site's attributes, identifies project risks, and promotes multiple project objectives. An inter-disciplinary approach also captures engagement with relevant community stakeholders.
- Protect and enhance the values and functions of natural ecosystems. WSD promotes a development layout, architecture, and construction methodology that avoids valuable or sensitive ecosystems and/or buffers these systems from potential impacts of stormwater runoff. A site's ecosystems can also be enhanced from a predevelopment condition to moderate any impacts from development.
- Address stormwater effects as close to source as possible. A site's layout can minimise impervious surfaces and thereby reduce stormwater runoff generation at source. Where runoff does occur, it can be captured and treated from the source to when it leaves the site, in multiple and complementary treatment approaches (a treatment train).
- Mimic natural systems and processes for stormwater management. 'Natural systems and processes' for stormwater management include infiltration, evapotranspiration and open stream systems. Treatment practices that mimic natural sytems and processes include living roofs, raingardens, swales and wetlands. All of these natural systems help to prevent stormwater runoff generation, and capture and treat runoff when it does occur. They also provide a suite of other ecosystem services and amenity benefits for a site, such as the moderation of heat, dust and light.