The growth in the frequency and severity of extreme rainfall has significantly increased the risk of flooding from rivers and urban drainage systems of insufficient capacity. It is a huge investment to dig into the earth and expand the sewer systems in urban areas, so other measures may prove to be better and cheaper alternatives. In fact, water from heavy rainfall may be dealt with in ways which will also have a great effect on the quality of urban life.
For the companies Copenhagen Energy and Frederiksberg Forsyning, Ramboll has carried out a complete overall flood risk calculation including an assessment of damages and the cost of adaptation measures. Based on these calculations, Ramboll and these companies are developing a climate adaptation plan where sustainable drainage and traditional sewer constructions are combined in the optimum way.
Sustainable urban drainage system
On the basis of the developed climate adaptation plans, alternative measures for handling rainwater were taken into account when the new Copenhagen district, Ørestad, was planned. The sewer system is designed as a 3-split system, consisting of sewage leading to waste water treatment plants, rainwater from roofs is let into surface canals and rainwater from roads is treated locally before it too is let out to the canals.
This local and sustainable drainage system helps avoid overload of sewers while also providing great educational and recreational value for the inhabitants of the area.