A climate change is occurring, and in the coming years, it is expected that in many urban areas heavy rain events will increase in intensity and frequency. This will become increasing problematic since the city sewerage systems cannot cope with sudden amounts of water. In dense urban areas, there is too little infiltration space for heavy rainfalls. The available space is either built up or intensively used as impermeable public domain. In some parts of the city, inundation occurred time after time, causing trouble and damage to public spaces as well as private properties. However, updating infrastructure is very costly, especially in urban environments. Finding funding to maintain existing storm water infrastructure is also difficult. Constructing
