In the last decade our cities have grown fast. To satisfy the rising demand of living space, green areas had to be used for building development. The consequence is an intensified land sealing which leads to a sustainable disruption of the natural water balance.
Fortunately, in the ‘80s a process of rethinking regarding the treatment of waste water management has begun. Regarding to the negative ecological and economic effects of the conventional principle of water diversion, a new solution had to be found. In contrast to the traditional diversion which has negative economic and ecological impacts, an urban drainage system could maintain the natural water cycle as far as possible.
Even the legislator recognized the necessity of an alternative (compare ATV 1999b). Furthermore, in 2007, the Water Framework
Directive of the European Parliament and of the Council came into force (Guideline 200/60/EG from 12.12.2006). Therein measures
are demanded which lead to a good chemical and quantitative status of groundwater and which ensure this permanently. in
the beginning of 2007. In this, measures are required which lead to a good chemical and quantitatively condition of the
ground water and to guarantee this permanently.
In the course of this, a legal regulation of this measures is also expected in Germany. In some regions of the country they
are already existing. A decentralized infiltration is already required in for example development areas.