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Using a Green Roof for Stormwater Management
Every green roof build-up delays stormwater run-off, where the water is detained at least temporarily. Run-off peak flows which can be critical for a sewerage system can be effectively capped. However, water storage in a green roof build-up cannot be increased arbitrarily because more water means greater growth intensity and this can lead to a transformation of the vegetation, requiring, for example additional maintenance. Water accumulation is sometimes created purposely for intensive green roofs to provide for capillary irrigation. However, in this case, the permanent retention of water of the roof is international on the one hand, but on the other hand the storage volume in the event of heavy rain is too limited to lighten the load on drainage facilities up and including the waterways, to the extent required. The necessary space can therefore be created by installing a grid spacer beneath the actual green roof build-up.
Why a stormwater management roof?
Changing weather conditions (e.g. extreme local rain events) can result in an entire public sewerage system being overwhelmed. One of the great benefits of a green roof is that it detains water and allows for the time-delayed run off of stormwater (water retention).
Water storage in a standard green roof build-up cannot be increased arbitrarily because more water could result in changes to the vegetation used.
However, this is possible with a stormwater management roof which offers this option in addition to all the other features of a green roof build-up.
Features of a stormwater management roof
Up to approx. 80 l/m² of precipitation can be retained with a stormwater management roof and then released into the sewerage system over a pre-defined period (between 24 hours and a few days). The space required for the increased precipitation is created by a grid spacer situated beneath the actual green roof build-up.
Meanwhile, the elements (water storage for the plants, air-water household in the root area etc.) that are of vital importance for the proper functioning of the green roof are all preserved.
Virtually all types of roof utilisation are possible above the stormwater retention space, once structurally permitted, from an extensive green roof to a roof garden with pathways and driveways.