The stormwater chain composition includes bioretention facilities, stormwater gardens and rain chains, rills and channels to rainwater harvesting and living roofs. By utilizing just one of these elements, you can help reduce stress on existing and overwhelmed stormwater drainage systems by breaking the conventional drainage chain of impervious surface (such as roof or pavement) to sewer.
Green roofs, as I will refer to them in this post, are layers of living vegetation installed on tops of buildings or structures. They manage run-off by reducing run-off flow rates from small to moderate storms and they also provide cooling in the summer months and reduce heat loss in the cooler winter months.
Green roofs are typically referred to as “intensive” or “extensive”. An extensive green roof is more lightweight designed for shallow root systems like sedum and moss communities and are easier to engineer and retrofit older, thinner roofs. Intensive green roofs can sustain larger shrubs and small trees and conifers. Green roofs can be biodiverse and visually pleasing, not monochromatic and boring as was the case in the earlier turf or grass roofs of Scandinavian log cabins.
When you plan your green roof, typically it contains a waterproof layer (membrane), a drainage layer, geotextile filter mat, the substrate (growing medium) and your vegetation referred to as your living elements. The simplest approach to planting is using smaller sized plugs or already grown tiles that can be supplied by certain garden centers. These plugs and / or tiles are planted directly into your substrate.
Green roofs are critical in reducing the amount of run-off that reaches our stormwater drainage systems, taking the strain off of older stormwater systems and deteriorating infrastructures in most urban areas. With roofs representing 40 – 50% of the impermeable surfaces in urban areas, you can see the potential role green roofs can play in reducing run-off.
Next week I will discuss another major component in the stormwater chain- capturing water run-off with landscape swales.
It would be wise to avoid plants that spread aggressively, since they can destroy the vegetative part of the green roof. This would be counterproductive and would lead to compromising the waterproofing. It would be best to determine if native plants can survive, since green roof environment receives more sunlight and wind that can be detrimental to the growth of some native plants.
ReplyDeleteMonica Barnes