High water, high rents: Poorest residents pay the most for climate adaptation

Cloudburst events and increasingly severe flooding threaten to make life wetter in the years ahead.

To address this challenge, cities across the world, including Copenhagen, invest in cloudburst tunnels and in separating stormwater from wastewater to reduce pressure on the sewers.

These measures are intended to benefit all residents. However, a new study from the University of Copenhagen shows that the costs of climate change adaptation are unevenly distributed. Tenants in not-for-profit housing and apartment buildings shoulder a larger share of the bill than owners in single-family houses.

“Climate adaptation is not only about flooding and sewer capacity. It is also about rising rents. Your type of housing determines how much of the bill you pay. Our case study shows that one-size-fits-all climate adaptation policies worsen urban injustice. Stormwater costs fall disproportionately on not-for-profit housing residents, despite Copenhagen’s reputation for climate leadership.” said Natalie Marie Gulsrud, Associate Professor at the Department of Geosciences and Natural Resource Management, University of Copenhagen.

She is first-author of the study “Housing Tenure, Climate Resilience, and Ecological Segregation”, published in PNAS.

The researchers analysed geographical data on climate adaptation projects and compared it with data on housing tenure and housing types. This revealed that not-for-profit housing is often sited closer to priority areas for climate adaptation.

“We can see that not-for-profit housing is often located where cloudburst routes are typically established. The problem arises when properties along these routes are required to separate stormwater from wastewater on their own land to connect it to the cloudburst system. This makes sense from a water-management perspective, but it can also impose substantial costs,” said Natalie Marie Gulsrud.

Water bills pay to keep stormwater at bay

Another inequality that the researchers noticed was the payment model. Not-for-profit housing developments typically consist of apartment blocks of four to six storeys. The increased drainage charges are calculated on the basis of drinking water consumption in each dwelling rather than on the amount of rainwater that actually runs off the roof into the public drainage system.

As a result, a four-storey building with a roof area of 100 m² pays four times as much as a comparable single-storey detached house if each dwelling uses the same amount of drinking water.

According to the researchers, the payment model favours single-family households. Consequently, multi-storey housing bears a disproportionate share of the financing of urban climate adaptation.

“It would be fair if payment reflected the amount of stormwater each property actually discharges into the sewer system. At present, charges are tied to drinking water consumption instead. There is a fundamental inequity in the way water bills are allocated and in how residents pay for climate adaptation and cloudburst management. As water charges continue to rise, the burden falls most heavily on the most marginalised members of society,” said Natalie Marie Gulsrud.

Who carries the cost?

The study identified siloed governance as a hidden root cause behind unequal adaptation costs. By improving the coordination between social and technical departments, the costs of climate adaptation and stormwater management could be distributed more evenly across social groups and support a fair green transition, according to the researchers.

“In this paper we hope to introduce a human aspect to a highly technical topic involving stormwater pipes, housing tenure, and climate financing,” said Natalie Marie Gulsrud.

“Who gets protected as the climate changes, and who carries the cost? A just transition needs social and technical governance working together, not on separate tracks. If we don't fix this, we risk deepening socio ecological inequalities in the green transition. We hope this research moves us closer to a transition that is genuinely just and caring.”

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[BOX] Case study: Hørgården

The researchers used Hørgården as a case study. The area is included on the Ministry of Social Affairs and Housing’s Prevention Areas list, and around 60 per cent of residents have an income below the Danish average.

As part of the implementation of a cloudburst conveyance route, Hørgården is required to separate stormwater from wastewater. Disconnecting roof run-off from the sewer system represents a significant expense for residents. Hørgården is an older housing development, and extensive sewer renovation and reconstruction will be required before the necessary climate adaptation measures can be completed. Ultimately, the costs are likely to be reflected in residents’ rents.