Why is drainage important?
Proper drainage ensures that the growing medium will be maintained in an aerated condition suited to health plant growth. Basal drainage must also be designed with large rainfall events in mind. The goal is for all rainfall to percolate to the base of the system. The portion that is not absorbed should move ‘underground’ toward roof drains or scuppers. During very large storms, brief episodes of surface runoff may occur. In a Roofmeadow® system, such surface runoff can enter the roof drains at gravel surfaced areas that surround the drain access chambers. Surface ponding, even during large storms, is evidence of a poorly-designed green roof.
