Rainwater management has been challenging for many jurisdictions, including the City of Vancouver, as population growth and climate change strain the drainage and sewer systems leading to implications for water safety. Urban rainwater runoff discharges directly to the sewer and drainage system and contributes to pollutants that are toxic to fish and other aquatic species. The green roof, a well-established green rainwater infrastructure, is an innovative approach to enhancing rainwater management and making the urban landscape more sustainable, environmental, and livable using vegetation.
From the literature review, a green roof ensures the quality and quantity of collected rainwater, improves building energy efficiency, absorb air pollutants, reduce urban heat island effect and gas house emission, bring aesthetic benefits, and preserve habitat for displaced creatures. The ongoing green roof performance has restrictions on many factors: substrate layer depth, temperature, moisture condition, weather events intensity and period, and proper operation and maintenance. Overall, green roof retains precipitation effectively even aged, with a higher percentage in a moderate climate.
Portland and Toronto prioritized on-site infiltration by green rainwater infrastructure in their rainwater management strategies and policies, although their approaches and requirements may differ. Portland and Toronto both have an independent green roof standard in addition to their rainwater management strategy. Portland focuses on a post-occupancy inspection program to monitor the green roof's ongoing performance, while Toronto established a Green Roof Bylaw to encourage the implementation of green roofs. Both cities have advanced strategies which could provide a valuable example with lessons learned from other jurisdictions, including City of Vancouver. This research aims to analyze the available green roof monitoring program in different cities with their establishing process and provide suggestions to jurisdictions for developing comprehensive monitoring programs in the private realm to ensure the implementation and performance of green roofs and other green rainwater infrastructures.