Hydrologic Performance of an Extensive Green Roof under Intense Rain Events: Results from a Rain-Chamber Simulation

Elena Giacomello and Jacopo Gaspari
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Elena Giacomello: Department of Architecture and Arts, Iuav University of Venice, 30135 Venice, Italy
Jacopo Gaspari: Department of Architecture, University of Bologna, 47521 Cesena, Italy

Sustainability, 2021, vol. 13, issue 6, 1-23

Abstract: The water storage capacity of a green roof generates several benefits for the building conterminous environment. The hydrologic performance is conventionally expressed by the runoff coefficient, according to international standards and guidelines. The runoff coefficient is a dimensionless number and defines the water retention performance over a long period. At the scale of single rain events, characterized by varying intensity and duration, the reaction of the green roof is scarcely investigated. The purpose of this study is to highlight how an extensive green roof—having a supposed minimum water performance, compared to an intensive one—responds to real and repetitive rain events, simulated in a rain chamber with controlled rain and runoff data. The experiment provides, through cumulative curve graphs, the behavior of the green roof sample during four rainy days. The simulated rain events are based on a statistical study (summarized in the paper) of 25 years of rain data for a specific location in North Italy characterized by an average rain/year of 1100 mm. The results prove the active response of the substrate, although thin and mineral, and quick draining, in terms of water retention and detention during intense rain events. The study raises questions about how to better express the water performance of green roofs.

Keywords: green roof; sustainably built environment; rain chamber; water management; water retention; water detention; intense rain event; runoff coefficient; rain peak; peak discharge; cumulative curve; soil sealing; NBS-nature based solutions (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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