Away from grey - towards more green and blue
A forward-looking approach to protecting cities from heavy rainfall – as well as heat and drought – is the sponge city principle. A large proportion of the rainwater or surface water is absorbed on site and stored locally. As soon as sufficient water is available in the ground or in cisterns for the irrigation of urban greenery, urban trees can develop healthily, and fulfil their functions as shade providers and natural air conditioners. Through evaporation and infiltration, rainwater and snow meltwater is returned to nature and the water cycle is closed.