Where does excess rainwater runoff go after the plants on the Green Roof Garden have soaked up as much as they need?
Excess rainwater from the roof filters down the building and ends up in the Rainwater Glen. The planting beds in the Green Roof Garden are made of several layers, beginning with a waterproofing layer, two layers of hard foam insulation, a root barrier fabric, a drainage tile to allow water to drain away from the roots, a filter fabric to keep the growing media from clogging the drainage holes, and growing media as the top layer. The semi-intensive media is a gravel-like soilless mix formulated specifically for roof gardens. It is lighter weight and more porous than soil, allowing water to drain quickly, thus reducing the weight load on the roof.
