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Photo: David Lagerlöf

Where heavy rain is a resource, not a problem

Uppsala is home to a unique stormwater runoff system that irrigates trees and shrubs and even delays water beneath the roadway. As well as being a smart way to use rainwater, this also reduces the risk of high water levels and flooding.

When the heavens open, all that water needs to go somewhere. It is important that the water can be diverted so that it doesn’t collect and cause flooding. In the new Rosendal district of Uppsala, the municipality has developed a concept to divert surface water to irrigate vegetation in the surrounding area. 

Thomas Blomqvist is a project manager at Uppsala Municipality’s Urban Planning Administration. He takes up the story:

“This is known as a green and blue water system and it is intended to promote green areas and vegetation while simultaneously treating rainwater as a resource rather than a problem. Large areas of vegetation require a great deal of water and this is one way of utilizing precipitation positively, even when it arrives as extreme rainfall. The system is designed to handle a one-hundred-year storm, a rainfall event that is statistically likely to occur once every century.”  

Unique investment

The urban environment of Rosendal is heavily planted. The idea behind the scheme is to store stormwater runoff beneath roadways for later use in irrigating vegetation. On its way to the plants through the soil, the water is purified of pollutants picked up on the roadway. Finally, the water is allowed to slowly run out into the ditches and waterways of the stormwater system. Due to the slow rate of flow, water and drainage systems are not inundated as they can be by high levels of stormwater. 

Many Swedish municipalities utilize similar water-management systems to a greater or lesser extent but what sets Uppsala apart is the scope of its scheme.

“We do this on a massive scale; Rosendal is a large area with several thousand residents. As far as I’m aware, there has been no similar investment anywhere in the world,” says Thomas Blomqvist. 

Extreme weather causes flooding

Uppsala’s green and blue system is part of the project Climate-assured System Solutions for Urban Environments. Björn Schouenborg, senior researcher at RISE, is the project manager. He explains that, as we experience more extreme weather events, interacting solutions that can handle large amounts of water are important.

“We can conclude that we will experience more and more serious floods. For example, Copenhagen suffered serious flooding in 2011 at an estimated cost of DKK 10 billion,” says Björn Schouenborg. 

The Swedish Civil Contingencies Agency (MSB) has highlighted 18 Swedish districts that face a major flooding risk, including Uppsala. Climate change, and the associated extreme weather, is one of the causes of flooding. Another is urbanization, as cities grow and green areas are supplanted by roads, parking and buildings.

“Here in Uppsala, we are working to ensure that we have ample vegetation in the central urban area. At the same time we are also making every effort to deal with climate-related challenges such as extreme rainfall. By treating rainwater as a valuable resource, we are being climate-smart and environmentally friendly,” concludes Thomas Blomqvist.

If you are interested in how we can create climate-smart cities you can learn more here:

Published: 2018-09-24