Queensland Sites and Projects
Bellvista Estate - Stages 3 and 4
introduction / images / location / Qld-Projects
Landscape Architect: EDAW AECOM
Location: Caloundra, Sunshine Coast, Australia
Client: Stockland
Listed as A Case Study for the AILA's 2008-2009 National Climate Change Project
Overview
The Bellvista Estate is located on the flat coastal plain of the Sunshine Coast adjacent to Lamerough Creek, 5 minutes from the coast and nestled between Caloundra Airport and Corbould Park racecourse. Bellvista is a residential neighbourhood designed with nature inspired streetscapes, a large central lake, extensive parkland, linked hike and bike trails and substantial street landscaping giving Bellvista a distinctive character and special appeal.
Underpinning Bellvista Estate is a network of bioretention pods, waterway channels, a wetland and a central lake accommodating the broader catchment area of Little Moutain.
When the EDAW team was initially engaged to undertake work on Bellvista in 2004, the project was a largely incomplete, poorly performing, unorganised collection of landscaped residential stages. Over the course of their involvement, EDAW has recognised and responded to the challenges presented by the extremely flat coastal plain and catchment area on which Bellvista is situated.
Central to this has been the successful application of a number of Environmental Principles, including changes to the soil structure, soil amelioration and placement, planting palettes, planting techniques, Water Sensitive Urban Design (WSUD) and the introduction of translocation. This has resulted in a landscape that can survive and perform in the harsh conditions experienced by the site, such as prolonged wet periods, resulting in flooding & extended water run-off, as well as extreme dry periods, typified by windy and salt laden conditions.
During Bellvista’s history EDAW, have bared witness to a fundamental change in the engineering practices between the traditional approach in stages of 1, 2 and 5 and the innovative WSUD approach by EDAW’s Ecological Engineering practice area in stages 3 and 4. This case study is focusing on the integrated installation of engineering and landscape as one process through bio pods and wetlands located within the stage 3 and 4 streetscapes.
The stage 3 and 4 streetscapes consist of approximately 500 lots ranging in size and in some instances located adjacent to conservation zones of natural heath land. Much of the development is on fill pads above the 100 yr average recurrence interval (ARI) flood level. The low relief of the site and that of the surrounding environment required careful consideration of urban drainage solutions to avoid the creation of expensive low gradient, large diameter pipe drainage networks that would not be able to free-drain into the shallow drainage channels that run through the site.
The only way to drain such deep piped drainage systems would have been to construct deep open water bodies at the pipe outfalls, and this approach would have resulted in extensive backwatering of stormwater pipes and attendant odour and pestilence issues (eg toads, mosquitos).
The use of above mentioned deep pipe outfalls would have generally precluded the application of best practice stormwater measures, such as bio-retention systems, required to deliver the water quality objectives for the site. The solution was to use small streetscape bio-retention systems, or ‘biopods’, to treat stormwater at surface before it enters piped drainage systems.
Core Landscape Principles
The integration of best practice water sensitive urban design with the landscape design for stages 3 and 4 of Bellvista was developed around the following guiding principles:
- Protect natural systems – protect and enhance natural water systems within urban development;
- Integrate stormwater treatment into the landscape – use stormwater in the landscape by incorporating multiple use corridors that maximise the visual and recreational amenity of developments;
- Protect water quality – improve the quality of water draining from urban developments in to receiving environment;
- Reduce runoff and peak flows – reduce peak flows from urban development by local retention/detention measures and minimising impervious areas;
- Add value while minimising development costs – minimise the drainage infrastructure cost of the development
Innovative approaches to planning and pre-design strategies
Integrating stormwater treatment into the landscape
Delivering best practice stormwater management on flat terrain is challenging. At Bellvista the urban design was informed by water sensitive principles which from an early stage identified that conventional drainage systems would not support end of pipe treatment systems. The need to treat stormwater at surface (before it enters underground drainage systems) was a driver for an integrated design process taking into account urban planning, traffic management, pedestrian and landscape design considerations.
Road drainage lengths and road leg lengths for vehicle speed control dovetailed to deliver an urban design where streetscape bioretention systems, or ‘biopods’ coincided with nodes of landscape embellishment. This process, whereby stormwater drainage informs the urban design rather than responds to it, is a key feature of the Bellvista Estate.
Adding value through collaboration
A willingness within Caloundra City Council to consider alternative stormwater treatment techniques on flat sites like Bellvista was initially borne from the perceived failures of ‘conventional’ end-of-line bioretention systems. By developing a collaborative relationship was with Council, greater consideration was given to stormwater during the Reconfiguration of Lot and Material Change of Use applications. This meant that the detailed design process was supported by having a highly considered urban layout that was conducive to at-surface stormwater treatment
Even with strong drivers for change, assessment of innovative solutions requires a significant shift in the traditional mind-set of assessment staff in order to confidently detail with the uncertainty inherent in new approaches. A key issue was the resolution of the perceived conflicts between the biopods and the current engineering guidelines and standard drawings. Council resolved this issue by assessing the proposal against the outcomes sought by the guidelines rather than looking for the conventional solutions which are typically provided to achieve those outcomes. These factors lead to delivery of an innovative design in a timely manner.
Innovative landscape design and management processes
Protecting Natural Systems and Water Quality
The ‘out-of-mind, out-of-sight’ approach to managing stormwater in the urban landscape is being revolutionised by water sensitive urban design. On flat sites stormwater must be treated to best practice standards before it enters the underground drainage system, such that the end-of-line approach to stormwater management is incompatible with this terrain. Sustainable water management is necessarily in the form of streetscape raingardens, and is therefore intrinsically linked to the urban design – Bellvista presents a model for the industry in integrating ‘functional landscape’ into urban design.
The development has been designed to ensure that no stormwater leaves the development without first passing through a local streetscape rain garden. The achievement of best practice stormwater management across the entire site represents a significant advancement in the sustainable management of water for urban development on flat terrain.
Within the development boundary, Bellvista preserves local wallum heathlands. Importantly it also protects the ecological values of high value downstream waterways by mitigating the hydrologic disturbance resulting from urbanization and managing runoff quality.
By capturing and detaining all low flows from the development in bioretention systems or the constructed stormwater wetland, the frequency and magnitude of disturbance to local waterways is significantly reduced.
The use of streetscape bioretention systems incorporated into nodes of landscape embellishment also means that stormwater that previously would have drained into underground pipes is instead used to sustain landscape. This passive irrigation offsets the need to use potable water for irrigation – which would otherwise be used to sustain landscape areas - and is consistent with the philosophy of using fit-for-purpose water supplies.
Innovative Construction Techniques
Typcially bioretention systems have been constructed at the time of bulk earthworks and civil construction associated with a subdivision. High sediment loads associated with construction sites can easily clog a bioretention system, so immediately after placing bioretention filter media systems have typically been covered in a sacrificial protective geofabric and turf layer for up to 12 months until allotment construction is mostly complete. After that 12 month period the geofabric is removed and the system is planted with functional species.
At Bellvista an innovative approach has been implemented that is a significant improvement on the standard approach to establishing bioretention systems. The bioretention systems have been designed to facilitate the early establishment of vegetation by locating the overflow in close proximity to the inlet. Temporary plywood barriers are then installed to partition this zone from the rest of the bioretention system, effectively excluding the majority of the system from sediment laden stormwater during the allotment construction period.
It can therefore be planted immediately following placement of the filter media, and a light application of mulch can also be applied mulch without risk of it being washed downstream. The filter media in the inlet zone is protected from sediment using geofabric and turf. After allotment construction is complete these protective measures are removed and the system is then operational.
Engaging the community to enhance outcomes for future generations
Bellvista brings sustainable land management back into the urban footprint – right into the local street. Catchment management is often most successful at small scales, and at Bellvista stormwater catchments are reduced to the size of just a few houses. Local residents directly engage with small streetscape rain gardens, and are prompted by visual cues that the health of their rain garden depends directly on their actions.
The receiving environment is no longer a remote waterway but immediately in front of their homes. This approach not only reflects ecological stewardship on the behalf of developer and Council, but promotes ongoing stewardship by local residents.
Engaging the community in Bellvista with water sensitive urban design in their neighbourhood is an important avenue to ensuring a local sense of ownership. Streetscape biopods establish a repetitive design language throughout the development, providing highly legible story of how the urban water cycle works, and in particular how stormwater directly sustains the local landscape, and how in turn the local landscape protects the local waterways.
New residents to the estate are provided with an informative flyer that outlines the role that the rain gardens play, as well as some simple do’s and don’ts to take care of them.
In addition, each bio-retention system is fitted with a small plaque as a subtle and friendly reminder to residents of the role that the bio-retention systems play. The wetland currently has temporary fencing in place until the vegetation establishes. Once the vegetation is established the fence will be removed. Interpretive signage has been installed to assist residents in understanding the ecology of the wetland including the role of dragonflies in mosquito management as well as botanical information on the plant species.
Engaging the children that live in Bellvista about water sensitive urban design in their neighbourhood is an important avenue to ensuring a local sense of ownership. Unity College is a newly established P-12 school within Bellvista Estate. The science teacher from the school has been engaged and informed of the innovative approach to stormwater management, and suggested environmental education learning activities - particularly in relation to the wetland - have been suggested.
As a further measure, all contracts of sale for properties located in stages containing bio-retention pods include a clause outlining the role of the bio-retention pods and state clearly the responsibility of the purchaser not to interfere with them, and specific Property Notes apply to houses with bio-retention systems located in the lot frontage.
Adaptive and Responsive Design Processes
Stormwater drainage in flat terrain is challenging enough without taking into consideration the need to protect fragile downstream environments. Bellvista presents a template for the sustainable management of urban runoff on flat terrain that is relevant to many coastal areas.
The project team operates in close collaboration with the Facility for Advancing Water Biofiltration (FAWB), a joint venture between EDAW’s Ecological Engineering group and Monash University. Rain garden designs are informed by the latest research findings, and assessment of the constructed systems at Bellvista is being fed back into research and published findings will further advance industry knowledge and practice.
All stormwater from Bellvista Stages 3 & 4 drains to vegetated treatment systems (either a bioretention system or constructed stormwater wetland) such that stormwater discharges from the site have a reduced load of pollutants compared with conventional drainage design. Based on MUSIC (Model for Urban Stormwater Improvement Conceptualisation) modelling, the mean annual load of total suspended solids (TSS), total phosphorus (TP) and total nitrogen (TN) will be reduced by at least 80%, 60% and 45% respectively.
Lessons Learned
The benefits of the integrated landscape and water sensitive urban design approach used for stages 3 and 4 for Bellvista are as follows:
- Reduced establishment costs for Developers – Research indicates the highest cost item associated with establishing bioretention systems is weeding. The Bellvista approach allows a light application of mulch to be used which dramatically reduces weeding costs.
- Improved Aesthetics for Residents – Early establishment of vegetation adds to the neighbourhood character and presentation which improves the marketability of the estate and liveability for early residents.
- Earlier water quality benefits – Plants are central to achieving the potential water quality benefits that bioretention can deliver. In terms of water quality, the sooner healthy plants are established the better.
- Reduced risk for Council – Since systems will be more established at the time of handover.
Team: EDAW, Stockland , Caloundra City Council , Brown Consulting , Cardno MBK, PMM
Budget: $1.5 million (capital cost of WSUD infrastructure)
introduction / images / location / Qld-Projects
uploaded April 2009
