NEWS 2024-04-19

How “free to use” models can help climate proof cities

Green areas and forest areas are effective protection against floods and cutting down forests in one area can lead to floods in another. Despite that, Swedish municipalities choose to fell and build – which increase the risks of high water flows. A recent study shows that existing ‘free to use’ models for calculating risks are effective tools for climate proofing cities.

View over the Kärra-Skogome area. Photo: Göteborgs stad

The risk of flooding in Swedish cities and in many other cities around the world is constantly increasing due to climate change. The consequences are already visible in the form of extreme weather with elements of more and heavier downpours.

In the future, cities will be subjected to even greater trials as the heavy downpours increase in scope, which also increases the importance of adapting construction of housing and infrastructure to the new conditions.

“We researchers talk about “mitigation” and “adaptation”, which means that we both want to reduce carbon dioxide emissions and at the same time adapt the way we build to be able to deal with the effects of climate change. A combination of nature-based and technical solutions will be required to climate-proof our cities”, says Åsa Gren, lecturer at University of Gävle and affiliated with the Beijer Institute.

A team of researchers at the University of Gävle, Chalmers University of Technology and the Beijer Institute has investigated the effects of torrential rain and increased water flows in the Gothenburg area, using an InVEST calculation model from the Natural Capital Project and data from the UN’s climate panel IPCC. InVEST models enables decision makers to assess quantified tradeoffs associated with alternative management choices and to identify areas where investment in natural capital can enhance human development and conservation. The Natural Capital Project is a collaborating partner of the Beijer Institute co-founded by Beijer Fellow Gretchen Daily and with Beijer director Carl Folke on the advisory board.

The study, published in the journal Land has examined Kärra-Skogome in northern Gothenburg, where there are building plans in an area that largely consists of forest. The results from the InVEST model, showing a great water retention potential of the existing forests and soils in this area, in combination with the upstream location of the planned development area, reveal an increased risk of large amounts of rainwater ending up in the city centre of Gothenburg if the forest is replaced by buildings.,  The ability of forests and green areas to absorb water constitutes an important ecosystem service that can protect against heavy rains.

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“Gothenburg’s topography makes the city extra vulnerable to torrential rain, as the central parts are low-lying. If logging is done at high elevation and upstream of the city centre, , the effects can be very large in central Gothenburg”, , says Åsa Gren.

The researchers now want more municipalities to adopt and use cost-effective and user-friendly calculation models, such as Invest, which is available for free online.

“We want the city planners to be able to clearly see where they can build, and where it makes more sense to plant or keep a green area or a forest. We can show that the calculation model is an effective tool for climate-proofing cities because it is a good decision support that provides a good overview, from the local to the regional. Sometimes a nature-based solution is best and sometimes you need to supplement with technical solutions., The most important thing is to make well-founded decisions”, concludes Åsa Gren.

This text is based on text by Anders Munck, Gävle University. Read Swedish text here

Reference: Egegård, C.H., M. Lindborg, Å, Gren, L. Marcus, M.B. Pont, and J. Colding. 2024. Climate Proofing Cities by Navigating Nature-Based Solutions in a Multi-Scale, Social–Ecological Urban Planning Context: A Case Study of Flood Protection in the City of Gothenburg, Sweden. Land 13(2), 143.