Risvangen, Aarhus
The project on the 50-hectare area Risvangen and Vorrevangen in northern Aarhus was initiated as part of the implementation of Aarhus Municipality's wastewater plan, where rainwater and wastewater were to be separated in the area. At the same time, the area had to be adapted to climate change to avoid overflow and consequent flooding and pollution of the bathing water in the bay at the bathing beach "Den Permanente". The project is the first large residential area in Denmark, where the separation of rainwater and wastewater is based on handling rainwater on the surface of the terrain. It was decided by Aarhus Water and Aarhus Municipality that the rainwater in the gardens and on the public areas in the area should henceforth be handled on the surface instead of in pipes underground, where possible. The advantage of rainwater solutions above ground is that larger rain events can often be handled for the same economy as with pipework, and that they can simultaneously add environmental and recreational value to the area.
The entire facility is dimensioned to be able to handle a 5-year rain event, with stowage to ground level. Furthermore, it is dimensioned so that in the event of a 100-year rain event, there will be a maximum of 10 cm of water above ground.
Due to problems with high levels of groundwater in the area and a very clayey subsoil, the rainwater does not seep down - except on some private properties. The individual parcels have been reviewed. For some, the terrain conditions are such that they can handle their rainwater on the surface, for others this is not possible, and they are connected to a rainwater pipe that later opens into the surface, or they have made local LAR systems with overflow to the road. The rainwater in Risvangen is delayed, evaporated or diverted at a pace that is suitable for the recipient of the rainwater. With normal rainfall, the rainwater seeps into the underground drains that lie beneath all rain beds and wadis. In the event of heavy rain, the drains will be filled with water, and the too distinguishable surface solutions will slowly fill up. The rainwater in the area ends up in Risskov Bæk and in the bay at Den Permanente. Rainwater management starts in the gardens and continues on the surface of the roads, in rain beds and wadis, and ends in a series of stormwater basins, which are designed as rainwater lakes with paths, benches and lots of wildlife.
Read more here
Grønne områder med klimatilpasning på terræn
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