Abstract: This presentation aims at audience who are interested in using green roof for stormwater management.

We will first explain the underlaying causes of stormwater challenges in the urban areas. Because of the lack of space at grade, cities are looking to the many unused rooftops for solution. Green roof is an effective source control tool with multiple co-benefits to offer. The plants and substrate absorb rainfall and reduce runoff volume. As water percolates through the substrate, peak flow is delayed and reduced.

We will discuss the concept of retention: quantify the effectiveness of lightweight water retention layers using water-retention-to-weight ratios and demonstrate their performance with a publicly available online Green Roof Retention/Evaporation Model.

We will also discuss the concept of detention: illustrate its importance in stormwater management, particularly during back-to-back storms, and compare various detention technologies on the market. Finally, we will introduce the new friction detention green roof, explain how it works and how it compares with existing technologies.

We will use video to explain the concepts and engage the audience using interactive polls.

At the end of the presentation, participants will be able to incorporate retention and detention into a green roof system and convert it into an effective stormwater management tool.