The creation of exceptional stormwater outcomes for new urban developments doesn’t just happen. It requires a bit of art, technical innovation, and a whole lot of collaboration to create healthy stormwater management facilities and urban waterways that also are places of amenity.
In this paper the stormwater journey to achieve excellent outcomes through collaboration is illustrated using the Prestons Development in Christchurch.
The demand for new urban growth areas in post-earthquake Christchurch put pressure on developers, Councils and their respective teams to produce new sections.
The Prestons development was one of those areas that was part way through a plan change process and stormwater management was an unresolved issue that required innovative thinking, and an understanding of the objectives of both developer, designer and Council to create a sustainable stormwater management system to provide the treatment and attenuation required as well as creating amenity that enhanced the living environment.
Through this journey there were many opposing opinions on the stormwater treatment systems that were required. For example wet first flush basins vs dry, many treatment facilities vs single large basins, and the operating level of the northern wetland, are a few of the technical differences that needed resolution.
Through this paper the overall stormwater context will be explained and some of the challenges will be expanded to describe how seemingly opposite goals can be worked through and eventually resolved to achieve exceptional outcomes for stormwater management and community amenity areas.
The Prestons development overall is 200ha was a combination of:
The development contributed to two separate catchments, The Styx River taking most of Prestons North, and Snellings Drain (a tributary of the Avon River) taking up the rest.
The whole site had very little fall from one end to the other and any unnecessary grading of the landform to the stormwater facilities resulted in significant volumes of imported filling.
The Styx River was considered to be less critical in terms of flow management but critical in terms of quality. Therefore the stormwater management required primary and secondary treatment utilizing a wetland.
The Snellings Drain had a proposed catchment wide wetland treatment facility that was proposed but had not been commenced at that time requiring patience. Downstream landowners were flood prone and therefore attenuation was required until an upgraded conveyance capacity to the proposed wetland was in place.
The final solutions, with a lot of help and input from the landscape designers, were developed through design processes and workshop and even a facilitated mediation process with the outcome being stormwater assets vested in Council that are assets to the community.