Summary
Summary
Fornebu is a brownfield development project with a focus on sustainable stormwater management and green infrastructure. The transformation of Fornebu, a decommissioned airport near Oslo, into a resilient, multifunctional urban landscape exemplifies nature-based stormwater management. Originally abandoned in 1998, the 340 ha brownfield site was redeveloped into a mixed residential and industrial area where stormwater systems were designed not as hidden infrastructure, but as visible, ecological assets. Swales, filter strips, permeable surfaces, detention basins and retention ponds were implemented to handle runoff and purify water, replacing conventional pipe networks. These measures were led and financed by Statsbygg (the Norwegian Directorate of Public Construction and Property), in collaboration with the City of Oslo, Bærum Municipality, and design input from Bjørbekk & Lindheim AS, supported by research from Interconsult ASA and Aalborg University.
From inception, the project aimed to enhance recreational and ecological values while ensuring cost-effective water management. Retention structures were sized to cope with flows from 1‑ to 20‑year return period storms, and water quality improvements were significant—modelled reductions of suspended solids (up to 90 %), phosphorus (≈ 65 %), copper (≈ 65 %), zinc (≈ 45 %) and nitrogen (≈ 40 %) were achieved.
Today, the Fornebu stormwater system is considered complete and serves as a meso‑scale model of blue‑green infrastructure integration, combining flood protection, water purification, biodiversity enhancement, recreational space and urban development stimulus. Its notable legacy is the shift from traditional stormwater management toward multifunctional, visible, sustainable urban design, resilient in the face of climate change and rooted in cross‑government collaboration.
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Overview
Year of issue
2025
Project
NWRM
Implementation status
Completed
Contact
Martyn Futter SLU
Location of the project
Fornebu is a 340 ha brownfield redevelopment of the old Olso airport.
Sponge measures implemented in the case study
Swales
Filter Strips
Ponds and scrapes
Basins
Permeable surfaces
Objectives
Regulation of hydrological cycle and water flow
Flood control and flood risk mitigation
Self-regulation of water by filtration / storage / accumulation by ecosystems
Natural assimilation (purification) of effluents through dilution, dispersion, and physicchemical processes
Flood control and flood risk mitigation
Self-regulation of water by filtration / storage / accumulation by ecosystems
Natural assimilation (purification) of effluents through dilution, dispersion, and physicchemical processes
Involved partners
| Authority type | Authority name | Authority role | Comments | Authority responsibility |
|---|---|---|---|---|
| National water authority | Statsbygg | Initiation of the measure | Statsbygg is the Norwegian Directorate of Public Construction and Property | Responsible |
| Other | City of Oslo | Determination of design details of the measure | Also secondary land owner | Responsible |
| Local water authority | Municipality of Baerun | Determination of design details of the measure | Municipality, typically responsible for infrastructure and green space | Supporting |
Site Information
Climate Zone
Cool temperate moist
Precipitation
778.00 mm
Temperature (°C)
6.00 °C
Evapotranspiration
200.00 mm
Imperviousness
40.00 %
Slope range
0-1%
Vegetation class
grass/turf
WFD Ecological status
Bad
WFD Chemical status
Failing to achieve good
Water quality status
Water quality was degraded prior to brownfield redevelopment. There is significant local pollution related to the old airport. Pollutants include oil, PAHs, heavy metals and de-icing chemicals.
Design and Implementation
Project scale
Large
Project scale specifications
Fornebu is a 340 ha brownfield redevelopment
Project area
340
Area subject to Land use change or Management/Practice change (ha)
340.00 ha
Size unit
ha
Basis of design
The measures are deisgned to treat a range of events with return times ranging from 1 to 20 years. Design criteria are based on long-term average summer rainfall.
Principles
Environmental responsibility and a need to balance competing demands were the key guiding principles behind the redevelopment plan. The plan was to develop a functional, multi-use urban area with recreational, residential and industrial areas. The development had to be acceptable to the general Norwegian public as well as area residents and administrators.
Factor constraints
The availability of the entire brownfield site for redevelopment greatly simplified the development of a master plan incorporating sustainable urban drainage features. While there were challenges with communication between different levels of government, these were resolved. The Statsbygg commitment to sustainable urban environments and substantial financial investment allowed this project to be implemented.
Constraints
Winter conditions, snow and ice are a challenge to the implmentation of sustainable urban drainage systems at Fornebu and other northern cities.
Favourable preconditions
Having a brownfield site and a governance environment favorable to sustainable multi use urban landscape were key factors in the success of Fornebu.
Financing
Total cost
2000000.00 €
Total cost information
Total cost is not known
Costs investment information
Total investment cost is not known
Costs land acquisition information
No land acquisition costs as land was already owned by Norwegian government
Administrative annual cost information
Administrative costs are not known
Compensations
No
Policy and Governance
Policy description
The old Oslo airport at Fornebu was a brownfield site in need of redevelopment. The urban planning challenge was to redevelop the site in a sustainable manner supporting both residential and industrial uses while encouraging environmental responsibility
Land ownership
Statsbygg (Norwegian Directorate of Public Construction and Property)
Policy targets
Runoff control
Peak-flow reduction
Pollutants Removal
Oher Societal Benefits
Increase Water Storage
Groundwater Recharge
Improved Biodiversity
Policy impact
| Directive | Relevant impact |
|---|---|
| Other non-EU | Storm Overflows |
| Other non-EU | Community (sustainable built environment) |
Policy challenges requirements
Norwegian government commitment to environmental sustainability : The Fornebu development was motivated primarily by national as opposed to European priorities.
Part of a wider plan
No
Public consultation
No
Has contractual arrangements
No
Impacts and Monitoring
Maintenance
Maintenance requirements
A similar level of maintenance as is needed for similar green infrastructure in other cities will be needed.
Socio-economic Impacts
Direct benefits information
The Fornebu brownfield redevelopment has clear direct benefits as it provides space for living, employment and recreation in a crowded urban area. The specific benefits of the measures in Fornebu are harder to quantify as they cannot really be considered in themselves but must be seen as part of the complete redevelopment picture.
Water-related ecosystem services include flood protection and security, wastewater services and improved coastal status due to a reduction in polluted runoff.
Water-related ecosystem services include flood protection and security, wastewater services and improved coastal status due to a reduction in polluted runoff.
Ancillary benefits information
Key ancillary benefits include more living space and a sustainable multi use urban environment supporting recreation, residential and industrial land use.
Biophysical impacts: Hydrology
Information on retained water
The total retained volume of water is hard to assess as the Fornebu plan consists of multiple measures.
Increased water storage
230.00
Increased water storage unit
m3/ha
Information on runoff reduction
Large qualitiative reductions in runoff peaks. The entire Fornebu master plan had a goal of runoff attenuation and control. The channels are designed to deal with flows of 1.25 m3 s-1 while the detention ponds are designed to handle a flow of 2.75 m3s-1
Information on peak flow reduction
Large qualitative reductions in peak flow could be expected when compared to the old Fornebu airport
Information on soil moisture
Extensive use of swales and soakaways will lead to improvements in soil moisture status and soil storage capacity compared to traditional impervious urban features. It is hard to make a “before / after” comparison in this case as the data do not exist and the change in land use is too large.
Biophysical impacts: Biodiversity
Improved biodiversity
Yes
Information on improved biodiversity
more aquatic habitat and greenspace
Biophysical impacts: Water & Soil Quality
Water quality overall improvements
Positive impact-WQ improvement
Information on water quality overall
based on mdeolling results and design criteria
Water quality improvements - Phosphorus (P)
60.00
Water quality improvements - Phosphorus (P) - Unit
% reduction pf pollutant
Water quality improvements - Nitrogen (N)
40.00
Water quality improvements - Nitrogen (N) - Unit
% reduction pf pollutant
Water quality improvements - Total Suspended Solid (TSS)
80.00
Water quality improvements - Total Suspended Solid (TSS) - Unit
% reduction pf pollutant
Water quality improvements - Copper (Cu)
65.00
Water quality improvements - Copper (Cu) - Unit
% reduction pf pollutant
Water quality improvements - Zinc (Zn)
45.00
Water quality improvements - Zinc (Zn) - Unit
% reduction pf pollutant
Soil quality overall improvements
Positive impact-SQ improvement
Information on soil quality overall improvements
Overall soil quality in Fornebu has been improved, primarily due to the removal of approximately 200,000 m3 of contaminated soil .This improvement is not related to green infrastructure, but to brownfield remediation.
Information on soil quality, overall soil pollution
brownfield improvement included removal of contaminated soil, PAH, oil and deicing fluids were all problems
Ecosystem erosion control
No
Lessons Learned
Key lessons
Success was dependent on communication between different levels of government and a clear vision for a sustainable, multi-use urban environment
Drivers
| Driver type | Driver role |
|---|---|
| Organisation committed to it | Main driver |
Success factors
| Success factor type | Success factor role | Comments |
|---|---|---|
| Financing possibilities | — | — |
| Attitude of decision makers | Main factor | Commitment of Statsbygg, to a sustainable, multi-use redevelopment of the Fornebu brownfield so as to support recreational, residential and industrial land use. |
| Attitude of relevant stakeholders | — | — |
Flexibility / Adaptability
It is unclear how flexible or adaptable Fornebu is to changing baseline conditions. Climate change may have both negative and positive effects. Warmer temperatures would reduce the problems associated with snow and ice. Changing precipitation patterns could alter the effectiveness of the Green Infrastructure for stormwater management.
Transferability
Fornebu provides a model for brownfield redevelopment and shows that sustainable urban drainage systems can be integrated into a multi-functional urban landscape.
Sources
Sources