Increasing rainfall means that pipe capacity is too small in many places, with excess water – a hazardous mixture of wastewater and rainwater – flowing into lakes, streams or sea untreated. The excess water also causes flooding of cellars, roads and green areas. In other words, we lack space in our sewer system, and Aarhus Vand is doing something about this by seeing surface water as a valuable resource.
We in Aarhus Vand are hard at work on separating rainwater and wastewater in areas where this has not already been done. We disconnect rainwater from the combined sewer system to ensure optimal capacity and maintain water quality. In our attempt to adapt the city of Aarhus to climate change and avoid damage to properties or infrastructure following heavy rain, we handle rainwater on the surface – wherever it is possible. In some areas though, rainwater is lead through new pipes, and in other areas we handle rainwater through a combination of surface solutions and through new pipes.
But primarily we handle rainwater on the surface. We do so because there is a potential for separating large areas for the same amount that it would cost to lay pipes. In addition, it offers a unique opportunity to use rainwater in a new way – for embellishment and recreational purposes.
We make rainwater a visible element in the form of rainwater lakes, rainwater beds and rainwater drains. We also establish hollows and dams; we create entirely new urban spaces and find new ways to lay out green areas. The municipality of Aarhus has a vision of making Aarhus an even more attractive place to live, and we support this ambition with our climate adaptation projects on the separation of rainwater and wastewater.
Whether we choose to lead rainwater through new pipes to a stream or handle it on the surface, we develop and prepare our sewer system for heavy rain – a direct consequence of climate change. Our choice of solution always depends on the local conditions. Furthermore, we keep measuring our efforts against the risk of flooding and the cost of the damage caused by flooding.
Aarhus Vand has carried out two major climate adaptation projects with rainwater being handled at the surface – one in Lystrup north of Aarhus and one in Risvangen in the northern end of Aarhus. In Lystrup all 12 climate adaptation solutions involved surface treatment. In Risvangen, rainwater is handled in a combination of surface handling and pipes. In Malling, a small town to the south of Aarhus, a new urban area has been planned to the south of the town, with the establishment of a drainage system for rainwater handling based solely on a surface solution.
At Aarhus Vand, we have taken up the challenge because we believe that handling of rainwater at the surface in the form of green solutions will provide significant added value to the citizens and support the municipality’s vision for the city.
Instead, all rainwater is handled on the surface using various sustainable drainage system (SUDS) elements. The local citizens can either choose to handle rainwater on their own plots and in return receive a financial reimbursement of the connection costs, or lead the water to a nearby public area via the surface, where Aarhus Vand handles it.
Getting the citizens on board was a difficult, yet crucial task. While some homeowners embraced the new recreational solutions, the project was also met with some resistance from more sceptical citizens.
The project team therefore had to be very thorough and convincing in their approach, and extensive efforts were made to ensure that the process of involving the citizens was steered in the right direction. A combination of workshops, extensive FAQ’s and even individual advisory sessions on private plots were conducted to ensure a successful implementation