If the available space is large enough and the ground is suitable, rainwater running off from roofs and paved surfaces can infiltrate directly into meadows and other green areas. The area needed for a ground infiltration plane is approximately 50% of the paved surface connected. Geiger et al., 2009
An infiltration-plane meadow on sufficiently porous ground requires a great deal of space but is low-maintenance. Underground infiltration systems are more efficient in terms of the space used but need regular maintenance. Infiltration-plane systems have a greater purifying capacity.
For the most part, water in infiltration systems can be drained visibly and aboveground to infiltration locations. The necessary slope for these facilities in soft, low bearing capacity soils is 0.5 cm/m. With greater distances to the infiltration system the required gradient of the slope becomes an important design criterion.