Moisture Measurements as Performance Criteria for Extensive Living Roof Substrates
Publication: Journal of Environmental Engineering
Volume 138, Issue 8
Abstract
Extensive living roof substrate design to promote storm-water management while balancing structural load and maintaining nonirrigated plant cover is investigated through linked laboratory and field experiments in Auckland, New Zealand. Setting quantifiable goals for the 2002 FLL guidelines and agronomic testing methods resulted in successful design of multiple nonproprietary substrates. Particle size distribution and quality control in the materials’ supply chain are critical. Additional work is required to define a meaningful standard permeability test for living roofs. While the maximum water capacity guideline provides a conservative estimate for structural loading when a substrate is wet, it should not be used to predict storm-water retention. Agronomic measures of readily available water (10–100 kPa suction) plus plant stress water (100–1,500 kPa suction) provide a reasonable estimate for the maximum potential rainfall storage during individual storm events. Subject to Auckland’s frequent rainfall, an extensive living roof with 70% v/v 4–10 mm pumice, 10% v/v 1–3 mm zeolite, and 20% organic matter at a 100-mm depth is recommended to maintain plants without irrigation (excluding drought conditions) and minimize weeds while preventing runoff from storms with less than 25 mm of rainfall.
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Acknowledgments
This study was funded by the former Auckland Regional Council, through the Storm Water Action Plan, and the former Waitakere City Council. Ongoing support is acknowledged from the (new) Auckland Council. Viewpoints expressed in this paper are those of the authors and do not reflect policy or otherwise of any of the Councils. The authors would like to acknowledge support from Earl Shaver, Matthew Davis, Hayden Easton, Professor Peter Brothers, and suppliers of substrate components, particularly Blue Pacific Mineral, Inpro, Bark Processors, and Dalton’s. The project has benefited from the input from colleagues John Dando, Craig Ross, Chris Winks, Nicollette Faville and the Environmental Chemistry laboratory of Landcare Research, and technicians in the Faculty of Engineering, University of Auckland—particularly Geoff Kirby, Jim Luo, and Alan Eaton. Finally, the authors would like to thank former students Emily Voyde, Yit Sing (Terry) Hong, Craig Mountfort, Patrick Oldendorf, Minyang (Mona) Liao, Simon Wang, and Laura Davies from the University of Auckland.
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Information & Authors
Information
Published In
Journal of Environmental Engineering
Volume 138 • Issue 8 • August 2012
Pages: 841 - 851
Copyright
© 2012. American Society of Civil Engineers.
History
Received: Jun 16, 2011
Accepted: Dec 22, 2011
Published online: Dec 27, 2011
Published in print: Aug 1, 2012
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