Conclusion
While green roofs and blue roofs are effective low-impact development tools, enhancing retention capacity and adding detention elements can take their stormwater management potentials to the next level. Enhanced retention green roofs not only reduce runoff, but they also lower irrigation needs and increase resilience to heat and drought.
Blue-green roofs and friction-detention green roofs incorporate detention to reliably manage back-to-back rainfall events and large intense storms, regardless of antecedent weather conditions when the roof is already saturated. While blue-green roofs work best on large dead flat roofs, friction-detention green roofs also work well on low-slope and sloped roofs, as well as irregular shaped roofs with many roof drains.
These advanced systems store a large amount of rainwater to be evaporated back to the atmosphere and delay runoff reliably during heavy downpour to minimize flood risks. Adding detention to retention on green roofs better manages stormwater and increases climate resilience in our cities.
Sasha Aguilera, B.Arch, GRP, is a design ambassador for Next Level Stormwater Management (NLSM), which provides tech support innovative stormwater management technology for projects in Canada (only). With nearly 15 years of green roof experience, Aguilera is recognized as a leading green roof design consultant. Aguilera has considerable experience working on vegetated roofs of various complexities—from retrofits to new construction—across the country. She was honored with the F. Ross Browne Award in 2017. Aguilera can be reached via email at sasha@nlsm.ca.
Karen Liu, PhD, is a green roof specialist at Next Level Stormwater Management (NLSM). Before joining the private sector, Liu was a lead researcher of the green roof programs at the National Research Council Canada (NRC) and the British Columbia Institute of Technology. In recent years, Liu was a key participant in the research consortium that developed the first national wind testing standard for vegetated roofing, the Canadian Standards Association (CSA) A123.24-15, Standard Test Method for Wind Resistance of Modular Vegetated Roof Assembly. Additionally, she has vast practical experience having worked on hundreds of green roof projects across North America, Europe, and Asia. At NLSM, Liu works on special projects and wind and stormwater calculations. She can be reached at karen@nlsm.ca.
