In the Stora Sjöfallet area of Stockholm Royal Seaport, the City of Stockholm has established criteria for climate-adapted and green spaces to increase well-being, promote biodiversity and to manage stormwater effectively.
The four developers that built a pre-school and 263 dwellings with occupancy in 2016 used the Green Space Index tool to meet the criteria. With the help of the tool – developed by the City of Stockholm – and improved processes, one of the most interesting current examples of multifunctional blue and green structures in a peri-urban, built-up residential area.
Climate change is set to transform management of the city’s green structures and stormwater management. In future, we can expect greater amounts of rainfall in autumn and winter and more frequent and prolonged heatwaves. This will increase stress on vegetation, with warmer winters and longer periods when people will be able to be outside.
The Green Space Index is designed to support system solutions whereby urban greenery and stormwater can be used in various ways to strengthen ecosystems, mitigate negative effects of climate change, and create pleasant spaces and outdoor environments.
The city’s toolbox
In 2008, the City of Stockholm decided that Stockholm Royal Seaport should be an attractive, resource-efficient and fossil fuel-free area and an international example of sustainable urban development in which new innovative tools, methods and approaches were developed and tested. The Green Space Index calculation tool was developed as one of the innovation-driving tools to achieve these goals.
In 2011, developers Wallenstam, SSM, Bonava, and Viktor Hansson were jointly granted land allocations in Stora Sjöfallet with binding requirements, including the fulfilment of the Green Space Index criteria and stormwater strategy.
What is the Green Space Index?
The Green Space Index is a calculation tool that was refined in Stockholm Royal Seaport. It was developed in Germany and further enhanced in Malmö. The index is a barometer of eco-effective spaces – i.e. spaces that positively contribute to an area’s ecosystem and local climate as well as social values related to vegetation and water.
The purpose of the Green Space Index is to contribute to ecosystem services that contribute to people’s well-being in the form of pleasant environments that enrich biodiversity, the management of stormwater to reduce flooding, increases in pollination rates, and reductions in temperatures during heatwaves. Green Space Index scores are balanced between different desired functions.
Green structures are used as an active component in the planning process. The Green Space Index is applied at block level and all developers need to work together to jointly achieve a Green Space Index rating.
Stormwater strategy considers stormwater as a resource. Stormwater is rain- and meltwater from roofs and other hard surfaces in urban areas.
The aim of the strategy is to build resilience to rising sea levels, to dimension stormwater systems to cope with heavy rainfall and intense periods of precipitation so as to prevent buildings and open spaces from flooding, and to capture stormwater to subsequently use it for watering plants.
Description of the green structures in Stora Sjöfallet
The blue and green structure that has been developed in Stora Sjöfallet, i.e. in opens spaces, and on facades and roofs, has resulted in well-thought out solutions that support both vegetation and stormwater mitigation. Key to the success of this project has been having correctly constructed plant beds with adequate soil depth, plenty of plants and connected stormwater solutions that supply water to vegetation.
The courtyard is made up of attractively designed narrow passageways adjacent to two larger, more open spaces. The two open spaces, each with their own design character, are connected by a footpath made of slate slabs laid in gravel. The courtyard is readily accessed from Jaktgatan and is connected by steps to the east and west, and by toe paths to Husarviken in the northwest. Light granite walls give the area character that distinguishes it from surrounding streets.
The courtyard’s landscaping is inspired by the Royal National City Park. The green spaces provide beautiful views from surrounding residential dwellings of rich environments that create a rural feel in a park environment. Rich vegetation of varying heights and plants that require light and shade respectively enhance the area’s biodiversity.
The northeast part of the courtyard consists of a grove of cherry trees and an open meadow. The trees form a shared canopy over gravel, and the area is furnished with hammocks. The landscaped meadow has a mowed grass area with space for picnics and ball games.
The southwest of the courtyard has a prodigious riparian wooded area with large oak trees and a moisture-fed undergrowth layer of fern plants, horsetail, and sedge. Here, excess roof water is led via ground-grated guttering and collected in a so-called rain garden-inspired wetland. Water is then stored in large barrels and used for watering and play.
Other stormwater is directed primarily towards planted spaces. Barrels located throughout the courtyard capture rainwater which is then used for splash-play and irrigation.
For children, there are sitting and climbing frames in solid wood, and sandpits. A wooden deck extends down the slope towards the beach park with beautiful views of Husarviken that catches the evening sun. A water sculpture is located to the northeast.
Lighting throughout the area has been designed to be restful. Orientation is enhanced by the highlighting of entrances with wall and ceiling lighting. Pedestrian walkways are illuminated with the help of bollard lighting. Effectful lighting enhances various locations throughout the park.
Sedum roofs are a recurring feature of the area and rooftop trees on joists have been added to one of the buildings. An interesting combination of solar panels and green roofs can be found on the roof of another of the area’s buildings. Vertical greenery has been applied to surrounding facades.
Stora Sjöfallet is one of the first projects in the development of Stockholm Royal Seaport that was required to meet Green Space Index requirement at an early stage. Initially, the City of Stockholm focused on creating common targets and increasing knowledge by inviting developers and consultants to a capacity development programme and seminar on sustainable solutions.
It was crucial that the developers’ landscape architect participated throughout the process, from its early stages right the way through to management, to ensure the green and blue functions were implemented, i.e. vegetation and water. This was done in collaboration with architects, civil engineers, and designers. To facilitate the collaboration process, a special project co-ordinator was hired and tasked with bringing together different requirements, detailed goals and actions within the area.
Developers in particular highlighted the benefits of “good conversations” with the City and the role of the project co-ordinator who ensured the project’s overall execution. During the various phases of the project, the City has called for updated Green Space Index calculations, reviewed documentation, and acted in an advisory role in discussions with the landscape architect.
Learnings for future projects
Creating a well-thought out green structure for a neighbourhood is very much about how different functions can be combined in a limited area. Basic functions in buildings and garages take up space on roofs and in other spaces. This can result in parts of an area, as well as roof space, being shaded. In Stora Sjöfallet, neither trees nor shrubs that produce edible berries and fruits could be planted because the area is largely shaded.
Safety reasons such as fire risk can also reduce Green Space Index ratings. In Stora Sjöfallet, for example, no dead wood could be laid on roofs.
In short, the City’s follow-up shows that the Green Space Index tends to be lower the more advanced a project is in its implementation. This may be because not all aspects of a project are technically feasible, that costs become too high, or that collaboration between different consultants has not worked as intended.
Another challenge is the transition of management plans from the implementation phase to the management phase so as to sustain the value of an area’s green structure for the long term. Capacity development of landscape contractors according to Green Space Index criteria will be a key issue in the future.
Impacts and outcomes
Developers were positive towards the Green Space Index tool, despite it being a new tool that meant another type of construction had to be planned. The fact that the City supported capacity development and promoted a shared vision were important factors that contributed to a successful outcome. The Green Space Index provided a source of inspiration for the landscape architect.
The clear scoring of different measures and plant selections given by the tool made it easy for actors to select different implementation alternatives. Resident surveys suggest that residents appreciate the design of the courtyards and the vegetation.
As part of the C/O City R&D project, NCC and Rise measured moisture levels on green roofs in Stora Sjöfallet. The survey suggested that green roofs neither adversely affect the underlying construction of buildings nor contribute to mould growth on materials under sealing layers during the period the measurements were taken.
As part of C/O City, calculations were made on the benefits of 55mm-thick sedum roofs similar to those used in Stora Sjöfallet. The conclusion was that sedum roofs do offer benefits in terms of supporting ecosystems, which are typically not understood until they have disappeared. This makes it extremely important to highlight the value of such roofs qualitatively, quantitatively, and financially.
Denser biotope roofs strengthen ecological pathways between green areas. In addition, calculations show that sedum roofs reduce stormwater flow by 40 per cent. This means that stormwater is retained on roofs which reduces the pressure on the stormwater network. In addition, sedum roofs contribute positively to the audio environment and absorb sound, achieving reductions in noise levels of about 2dB. Green roofs reflect light, which means that heat is not stored to the same extent as on sheet metal roofs. During heat waves, green roofs can reduce temperatures by up to 5C.
Green roofs fitted with solar panels have a positive synergy effect since green roofs have a cooling effect and thus improve the efficiency of solar panels.
Green Space Index-driven innovations in brief
Innovation is not only about new technologies and new materials but can also be about how we use plants and nature in new ways in urban environments. Work with the Green Space Index and stormwater strategy in Stora Sjöfallet has driven the development of varied and rich urban vegetation, which in turn has resulted in a high level of well-being:
- Greenery is not only at ground level; the area also has a large number of green roofs, vertical greenery on facades and rooftop trees on joists. Green roofs help to strengthen ecological distribution paths between green areas, reduce stormwater flow by 40%, reduce noise levels by around 2dB, and reduce temperatures by 5C.
- Well-thought out stormwater solutions with key elements of ecosystem services and multi-faceted stormwater management.
- Large oak trees on joists.
- Planted areas included many different species of plants with a variety of functions.
- In-house developed Excel-based planning tool to support the selection of plants.
- Meadows in urban settings.
- Meeting areas in open spaces for socialising that have carefully considered design elements.
- Spaces for children based on playful designs with spaces themselves functioning as toys.
- Combination of solar panels and green sedum roofs contributes to positive synergy effects.
- Stora Sjöfallet’s green spaces show that remediated industrial land can be transformed into green oases in the city.
Potential and future applications
Building cities that can withstand rising sea levels and cope with increased and more intense rainfall is a major global challenge. In Stora Sjöfallet, this has been achieved through a combination of green spaces, green roofs, vertical greenery and smart stormwater solutions. The Green Space Index and stormwater strategy are important tools that can be adapted to local conditions and thus applied in future housing construction projects in Sweden and elsewhere in the world.
Many different types of green spaces that interact with stormwater solutions in a city neighbourhood enable smart solutions to be developed where “nature does the work”. Stora Sjöfallet is a showcase for Swedish urban construction that can support the export of Swedish expertise in climate adaptation, architecture and landscape architecture, involving large numbers of actors and companies.
- Wallenstam has built 121 rental dwellings and a pre-school in this phase. Designed by VERA Arkitekter.
- Construction company Viktor Hanson has built 30 tenant-owned dwellings in this phase. The architect is Joliark.
- SSM has built 48 tenant-owned dwellings in this phase. The architect is Arkitema.
- Bonava has built 64 tenant-owned dwellings in this phase. The architect is Brunnberg & Forshed Arkitektkontor.
- Landscape architects Urbio designed the courtyards spaces and calculated the Green Space Index for the block.