In the past, urban drainage meant draining precipitation water as quickly and completely as possible in order to reduce the risk of flooding in the town. Nowadays, the aim is to have as little impact as possible on the natural balance of the water cycle through "near-natural" handling of rainwater. This brings not only water management but also financial benefits. Rapid drainage of water impairs groundwater recharge and shifts the risk of flooding to downstream residents.
The basic principle of all construction activities should be to intervene as little as possible in the water balance, for example by using water-permeable surfaces or green roofs. However, if the impact cannot be avoided, it can at least be limited through near-natural, decentralized stormwater management. Therefore, low-polluted rainwater (for example, from roofs and courtyards, private and municipal roads) should be infiltrated on site, collected and used (for example, for watering gardens or flushing toilets), or at least retained in a decentralized manner and discharged in doses into streams and rivers. In most cases, no permit is required for the infiltration or discharge of precipitation water if the relevant technical rules are observed.