REINVENTING THE TRADITIONAL VEGETATED ROOF FOR RAINWATER DETENTION: “A detention layer in vegetated roof systems helps manage the excess rainwater runoff onsite by mimicking friction found in watersheds and aquifers,” states Sasha Aguilera in an informative reference on green roof concepts and technologies

Note to Reader:

In its weekly Waterbucket News e-newsletter series, the Partnership for Water Sustainability in BC strives to feature champions who are leading changes in practice in the local government context, changes that will help achieve this over-reaching vision or goal: IMPROVE WHERE WE LIVE!

In this article, the Partnership looks outside British Columbia to feature Sasha Aguilera. Her work as an advisor on various vegetated roofing projects across the country has established Sasha’s reputation as one of Canada’s foremost green roof professionals. 

Sasha Aguilera has co-written an in-depth and well-researched article that is an informative reference on green roof concepts and technologies. The Partnership is showcasing this work because we believe it will be of interest to a range of readers, from the merely curious to the serious practitioner. Combining retention and detention in vegetated roof design is a technological innovation inspired by nature, and is an application of whole-system thinking.

Modern Vegetated Roofs Bring Nature Back to the City

“Put simply: the modern vegetated roof is designed to drain extremely fast. That is not to say no one has considered alternatives,” states Sasha Aguilera. “Slowing down water to create detention has been tried in vegetated roofs, albeit with mixed success.

“There are a few examples of great success, but replicability and widespread adoption have been difficult to achieve. This is unsurprising, since creating detention in a thin vegetated system is challenging. However, innovations are changing that equation.”

Among the various features of a friction-detention vegetated roof, most advantageous is that it can temporarily store and passively release 75 to 100 mm (3 to 4 in.) of rain and can be applied on low-sloped roofs.

Friction-Detention Technology Emulates Nature

“Vegetated roofs, more commonly known as green or live roofs, are a sustainable solution emulating and echoing designs found in nature in response to modern human challenges. This nature-inspired innovation is known as biomimicry,” states Sasha Aguilera.

“As climate change presents an increased risk, implementing green infrastructure has become a key tool to help manage rainwater where it falls, and thus increase community resiliency. Modern vegetated roofs bring nature back to the city for a plethora of benefits, using available space on rooftops.

“Traditional vegetated roofs achieve retention by holding a certain amount of rainfall onsite. After they are fully saturated and retention is maximized, additional rainfall drains through as quickly as it falls. Now, a detention layer in vegetated roof systems helps manage the excess runoff onsite by mimicking friction found in watersheds and aquifers.

“Friction in nature includes tall grasses in meadows, dense masses of reeds in wetlands, or layers of leaves on a forest floor. Friction-detention in vegetated roofs is a technological innovation inspired by nature to achieve rooftop water balance management in dense urban areas.

“Friction-detention technology offers uniformity and redundancy. Detention is activated by the friction-detention layer’s own large surface rather than relying on a single-flow restrictor at a roof drain (which can fail or clog),” concludes Sasha Aguilera.

To Learn More:

Download a copy of Reinventing the traditional vegetated roof for detention.

Then watch the simulation video on YouTube.

Contact Sasha Aguilera directly at and/or phone number 416 637-5772 x 2