In Norway, buried streams are being brought back into the open as towns and cities prepare for heavier rainfall. Research at a university campus south of Oslo suggests that restoring surface waterways can also improve water quality, create habitats for wildlife and make public spaces more attractive.
For decades, streams were diverted into underground pipes to make room for roads, buildings and agricultural land. But as climate change brings more intense downpours, drainage systems designed for past conditions are coming under increasing pressure.
Jan Vermaat, professor of aquatic ecology at the Norwegian University of Life Sciences (Norges miljø- og biovitenskapelige universitet, NMBU), explained the problem in an article published on 8 October by forskning.no.
Today’s stormwater pipes were often built for a different climate than the one we have now.
The alternative being explored is to give water more space above ground, using streams, ponds, wetlands and vegetation to manage rainfall where it falls.
What happens when buried streams are reopened?
At NMBU’s campus in Ås, researchers have been studying Campus Creek (Campusbekken), an approximately 950-metre network of interconnected streams, ponds and constructed wetlands.
The system combines older water features with newly created open channels, whose downstream sections were completed in 2020. Previously, much of the campus runoff was directed through underground pipes. Today, the water passes through a series of landscaped areas before reaching Lake Årungen and eventually the Oslofjord.
A peer-reviewed study published in the Norwegian Journal of Water in 2026, bringing together findings from five master’s research projects, examined how the system performs.
Water samples collected at five locations between June and October 2022 showed lower concentrations of nitrogen and phosphorus downstream, along with reductions in several metals, including copper, nickel and lead.
These substances can enter waterways through surface runoff. Excess nitrogen and phosphorus can also contribute to the pollution of lakes and coastal waters.
Researchers suggest that aquatic plants, algae and microorganisms absorb some of the nutrients, while particles settle as the water moves more slowly through ponds and wetlands.
The findings indicate that the creek helps improve water quality before runoff enters the wider water system. However, the study does not establish a precise overall reduction in pollution loads, and comparisons with older drainage measurements are complicated by changes to the campus over time.
New habitats in an unexpected place
The environmental benefits extend beyond water quality.
Within three years of the newer sections being completed, researchers documented breeding populations of common toads, common frogs and smooth newts in the creek system.
A vegetation survey in 2024 recorded 128 plant species, including 11 species on Norway’s national Red List, which identifies species facing varying degrees of extinction risk within the country.
Some of these threatened plants had been deliberately introduced through landscaping, while others established themselves naturally.
Researchers also recorded a red-listed damselfly and the northern bat, a species classified as vulnerable in Norway.
The findings illustrate how urban green spaces can provide habitats for wildlife, including species that might otherwise be associated with more natural environments. Nevertheless, none of Norway’s three red-listed amphibian species was found in the campus creek.
The project has also affected how people experience the landscape.
A survey involving 131 students, employees, local residents and other visitors found that respondents generally appreciated the water features and surrounding vegetation. The ponds and more natural-looking areas were particularly well received.
For the researchers, this shows that blue-green infrastructure, meaning connected networks of vegetation and water features, can serve several purposes simultaneously: environmental protection, stormwater management and recreation.
Oslo is already putting the approach into practice
The experience at Ås is part of a broader shift in how Norwegian cities are approaching stormwater management.
In Oslo, several previously buried waterways have already been restored. The Hovinbekken stream, for example, has been brought back to the surface through sections of the capital, including Bjerkedalen and Klosterenga.
According to the City of Oslo’s climate agency, these projects help manage runoff during heavy rainfall while creating greener neighbourhoods.
The city’s 2026 climate budget includes continued work to reopen sections of Bakåsbekken, Gaustadbekken, Refstadbekken and Østensjøbekken.
Oslo has also committed to restoring at least one substantial section of watercourse each year.
The principle is relatively simple. Rather than directing rainwater into underground infrastructure as quickly as possible, cities can use open waterways and vegetated areas to slow its movement, retain some of it temporarily and allow some to infiltrate the soil.
Such measures can complement conventional drainage systems while providing environmental and recreational benefits that underground pipes cannot offer.
Why restoring a stream is not always enough
Reopening waterways is not an automatic solution to urban flooding or ecological degradation.
The Campus Creek research provides evidence of improved water quality and suitable habitats, but it did not quantify how much stormwater the system absorbs or how far it reduces flood risk.
Its findings therefore cannot be used to calculate the flood protection that similar projects would provide across Norway.
The researchers also identified practical challenges.
During summer measurements, water temperatures in parts of the campus system reached 32.9°C. Shallow streams exposed to direct sunlight can become too warm for species that depend on cooler water, particularly fish.
Trees and natural vegetation along the banks can provide shade, helping regulate temperatures and create more resilient habitats.
Maintenance presents another challenge. Vegetation can slow water and support wildlife, but excessive growth can obstruct channels and drainage outlets. Researchers also identified nine plant species on Norway’s alien species list, underlining the need to control potentially problematic vegetation.
Design, monitoring and regular maintenance are therefore essential, particularly where restored streams pass through densely developed areas.
The lesson from Ås is not that cities can simply replace underground pipes with natural waterways. It is that water management, biodiversity and public space can be planned together.
As Norwegian municipalities adapt to more intense rainfall, restoring buried streams represents a change in urban design: instead of treating water solely as something to remove, cities are beginning to make room for it.
