Why does rainwater increasingly have to be infiltrated on private land?
Why does rainwater increasingly have to be infiltrated on private land?
The construction of a building or infrastructure means that rainwater can no longer seep away or evaporate in the same way as before due to the associated sealing of the ground. These interventions in the natural water cycle have a significant impact on the microclimate.
The conventional method of draining rainwater from buildings is to collect it in rainwater pipes and discharge it via the street sewer (combined or separate system). In this way, the water is removed from the natural cycle and not fed into the groundwater. The cooling effect of evaporation is also eliminated. The fact that the construction and maintenance of sewer systems is associated with considerable costs is a further disadvantage.
There are several options available for infiltrating rainwater:
The area infiltration
comes closest to natural infiltration. Here, rainwater seeps into the ground via open, green or permeable paved surfaces.
With retention area infiltration, the rainwater is channelled to a sealed pond, wetland or ditch, where it is stored and only fed into the ground via a nearby infiltration area or via open embankments when water levels are high.
With swale infiltration, on the other hand, the rainwater drained from paved surfaces is temporarily stored in shallow, grassed swales / depressions before it seeps into the ground. Another type of infiltration swales are the so-called "Raingardens" (rain gardens). These swales are preferably planted with wild plants that have an ornamental value and are adapted to alternately moist soil conditions.
Pipe or infiltration trenches allow the water to seep into the subsoil via perforated pipe systems.
Trench infiltration systems combine the advantages of both systems.
[Source: www.klimawandelanpassung.at]
Infiltration via underground retention basins is not an ideal method of choice, as the rainwater is channelled directly into the groundwater and the positive effect of evaporation is lost.
Another measure is to store rainwater. This can be done on buildings, for example, by greening roofs and façades. These green spaces not only relieve the sewer network during heavy rainfall events, but also serve to keep the air clean, protect against heat and also contribute to a potential increase in biodiversity. A distinction can be made between intensive and extensive green roofs. Extensive green roofs have a low build-up height of approx. 10 cm of substrate, where the plants are largely self-sustaining and maintenance is correspondingly low. The water storage volume here ranges from 25 to over 60 litres per m². Intensively managed green roofs are a fully-fledged and completely usable green area on the roof with a water storage volume of 60 to over 150 litres / m².
Especially in times of climate change and the associated increase in heavy rainfall events, sustainable rainwater management is an important aspect of conserving the valuable resource of water.
