Hydrological performance of a full-scale extensive green roof located in a temperate climate

• We investigated the hydrological performance of a extensive green roof.
• The roof is a full-scale system installed in 2007 in Leeds, United Kingdom.
• The monitoring took place over a 20 month period.
• The green roof was found to effectively retain and detain rainfall during storm events.
• Retention was found to correspond significantly with rainfall depth, duration, intensity and prior dry weather period.

Increasing recognition is being given to the adoption of green roofs in urban areas to enhance the local ecosystem. Green roofs may bring several benefits to urban areas including flood mitigation. However, empirical evidence from full-scale roofs, especially those that have been operational for more than several years is limited. This study investigates the hydrologic performance of a full-scale extensive green roof in Leeds, UK. Monitoring of the green roof took place over a 20 month period (between 30th June 2012 and 9th February 2014). The results indicate that the green roof can effectively retain and detain rainfall from the precipitation events included in the analysis. Retention was found to correspond significantly with rainfall depth, duration, intensity and prior dry weather period. Significant differences in retention values between the summer and winter seasons were also noted. Regression analysis failed to provide an accurate model to predict green roof retention as demonstrated by a validation exercise. Further monitoring of the green roof may reveal stronger relationships between rainfall characteristics and green roof retention.