Photo: Marion Jørgensen

Protecting cities from extreme rainfall

Wednesday 07 Oct 15

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Karsten Arnbjerg-Nielsen
Professor
DTU Environment
+45 45 25 14 50

It is no longer simply a question of designing ‘smart cities’. We need to create ‘smart liveable cities’ that use rainwater to improve quality of life and make city living desirable.

We all want to live in a good city. We must also ensure our cities can handle extreme rainfall, and prevent flooding of basements and roads, as was the case when Copenhagen in 2011 was hit by its worst cloudburst so far. According to experts, rainfall volumes will only increase in the future.

Denmark must therefore protect its cities against extreme rainfall events, says Professor Karsten Arnbjerg-Nielsen, DTU Environment.  In three different projects in Aarhus, Copenhagen, and Australia, respectively, he is investigating not only how to create innovative energy systems in ‘smart cities’, but also how to create ‘smart liveable cities'. Here, DTU is currently assessing the value of using drainage soakaways, water storage, and channelling excess water to areas where flooding does not cause widespread damage to relieve pressure on urban sewer systems.

Value for people
“We want to create cities that are not only technically sophisticated, but also pleasant to live in. Reducing the risk of flooding simply by laying down larger pipes or constructing cloudburst roads isn’t a financially viable solution. We have to think about the value for the people living in the city,” says Karsten Arnbjerg-Nielsen.

Based on an assessment of how happy people are living close to a park or other recreational area, for example, the researchers perform socio-economic calculations to determine the potential for green and blue solutions. This is done by comparing calculations and scenarios with the cost of installing larger drain pipes, managing surface water or living with flooding from the sea or heavy rainfall.

Copenhagen is well-prepared
Karsten Arnbjerg-Nielsen points to the City of Copenhagen as a good example of how to plan for future climate change. Here, city planners will create a blue and green city with recreational facilities and increased biodiversity.

“We have examined the effect of Copenhagen implementing its climate adjustment plan in a world that might be six degrees warmer than expected. Everything suggests that this will not be a disaster. Copenhagen is well-geared to future climate change and has chosen to adopt a radical approach by building an extremely large rainwater pipe as well as implementing many small changes such as raising the kerb and retaining and utilizing rainwater locally.”

“Taken overall, this kind of climate plan ensures a good environment for nature and people in the form of clean bathing water and lower emissions of heavy metals to coastal areas and the sea. These are the kinds of solutions we want to help create for the future,” says Karsten Arnbjerg-Nielsen.

Article from DYNAMO no. 42, DTU’s quarterly magazine in Danish.