dcsimg Here comes the flood... and it can make cities flourish - Ramboll Group
     
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Here comes the flood... and it can make cities flourish

Extreme rainfalls deluge our streets and overwhelm our drainage systems, resulting in costly clean-ups. But by adapting cleverly, cities can turn this around and start capitalising on stormwater.

 
 

By Kristine Barenholdt Bruun

An August evening in 2010, Thomas Lykke Pedersen, the Mayor of Fredensborg Municipality north of Copenhagen, Denmark, was on his way home when heavy rain started to submerge the streets. He decided to leave the car, dragging himself through knee-deep water to a residential area with flooded gardens and water gushing from the sewers. As the mayor helped a young girl move a television and stereo to the safety of her home’s upper storey, he realised that something had to be done to prevent this from happening again.

“It was the heaviest rainfall on record in Kokkedal and a terrible eye-opener. We had to evacuate some of our residents. In retrospect, I wish we had started to climate-adapt the town much earlier,” the mayor says as he looks back at the 2010 event.

Easy access to nature in Kokkedal. SCHONHERR/BIG

The blue and green garden city

Today, Kokkedal, a town in Fredensborg Municipality, has undertaken Denmark’s largest climate adaptation plan to date, called the Blue-Green Garden City. It is a project that not only safeguards against water damage but also manages to capitalise on stormwater and use it for aesthetic, social, and  health-promoting purposes.

Jens Veggerby, a climate adaptation and flooding expert at Ramboll and head engineer on the Blue-Green Garden City project, explains:

“We handle the rainwater on the surface and use it for aesthetic and recreational purposes. Crucial parts of the adaptation plan are the expansion of an existing stream, the restoration of the original water cycle, and the creation of a delta to make the water flow through the city.”

Together with a team of landscape architects from Schønherr and engineering consultants from Ramboll, Jens Veggerby is working to transform Kokkedal into a resilient town through ecosystem based adaptation or so-called blue and green infrastructure.

Kokkedal is far from being an isolated case. Cities around the globe are developing adaptation plans to deal with the consequences of climate change. And for good reason. The UN Climate Change Strategy 2014-2019 projects that rising sea levels, heavier rains, inland flooding, stronger storms and more extreme temperatures are going to have a global impact on the hundreds of millions of people living in urban areas vulnerable to climate change.

 

Adding more value to climate adaption

According to the UN Climate Change Strategy, the world’s cities cannot avoid adapting to climate change, but how should they go about it? And how can they add value beyond the obvious climate benefits?

Luna Khirfan, Professor of Urban Planning and Design at the University of Waterloo, Ontario, explains:

“Every context suffers from different vulnerabilities. That said, I endorse any approach that works with the ecosystem and provides solutions that cities can capitalise on, for example, by harvesting rainwater or adding green surfaces instead of hard non-porous surfaces like asphalt and concrete that not only capture and reflect heat, but also exacerbate flooding.”

She continues:

“An ecosystem-based approach improves the quality of life since more greenery creates more comfortable, recreational and aesthetically pleasing spaces.  Ultimately, it has a positive impact on the community, encouraging people to enjoy their public spaces and feel a greater sense of civic pride and cohesion through their common enjoyment of well-designed public spaces.”

Flooded residential area in Kokkedal, Denmark. POLFOTO

When water creates community spirit

In Kokkedal, residents are grappling with more than the severe consequences of heavy rains. The run-down town is socially divided and has a reputation as an area with juvenile crime. To address these problems, the town has made social cohesion and safety a crucial element of its climate adaptation  plans, using water and greenery to establish outdoor areas that can bring people together and give the area a much-needed boost.

“Creating attractive areas, more interaction between citizens and open spaces that feel safe are the cornerstone of the adaptation plan. At the same time, we hope our citizens will have something to be proud of and a positive story to tell about our town,” says Mayor Thomas Lykke Pedersen.

Professor Khirfan sees Kokkedal as a prime example of a clever, ecosystem-based approach to adaptation, because it focuses on dealing with surface  rainwater through greenery, lakes, stream restoration and stormwater basins – all features that create more value for both residents and the ecosystem. Kokkedal is giving itself an extra layer of blue and green infrastructure – a fourth dimension of water and greenery that ensures both climate adaptation  and aesthetically pleasing recreational areas.

Jens Veggerby, Ramboll’s head engineer on the Kokkedal project, agrees that it makes good sense to see rain as an asset rather than a liability.

“Water is a valuable resource, and climate change adaptation is about minimising negative impacts and capitalising on the possible opportunities,” Jens Veggerby explains, continuing:

“One of our big concerns is to establish a visual and social connection between water in parks and residential areas by making the water branch out between the buildings, which is  visually appealing. Such solutions also enhance the ecosystem, property prices, social cohesion and well-being.”

Seizing green and blue possibilities

In Kokkedal, the first phase of the climate adaptation project has already been completed. Mayor Thomas Lykke Pedersen strolls through the large green and blue recreational area with its restored stream, crossing a wooden bridge over one of the newly established retention basins. The basin perfectly resembles a natural lake, replete with tall reeds and rushes, insects  buzzing on the water surface and small fish swimming beneath. Stopping on the bridge, he points to a cluster of homes located close to the climate-adapted area:

“These are the houses that were most damaged in 2010. We’ve now built a dike and widened the water into a broader river with double profile. Hopefully, this will prevent our town from re-experiencing the damage we suffered in 2010,” he says as he steps off the bridge onto the newly constructed footpath.

The mayor walks another few hundred metres to the end of the blue-green area, entering a residential area built of drab concrete and asphalt:

“We haven’t started on this area yet, but when it’s finished in 2017, the water will be detained here and branch out between these houses, and new greenery and cherry trees will be  planted. I think it will make the citizens of Kokkedal proud,” he says.

 

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Contact

Jens Veggerby
Jens Veggerby
Project Manager
T+45 51617934
Ejeve@ramboll.dk