Author(s): Aung Naing Soe; Asaad Y. Shamseldin; Kilisimasi Latu; Conrad Zorn; Sihui Dong; Zoe Avery; Rachel Devine; Robyn Simcock

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Keywords: Green roofs; Urban stormwater management; Runoff control; Hydrological performance; Nature-based solutions

Abstract: With increasing urbanization and climate-induced shifts affecting precipitation patterns in New Zealand, green roofs can provide benefits within urban stormwater management. A green roof research facility has been set up to monitor the hydrological performance of green roofs at the University of Auckland in collaboration with the Auckland Council. Seven experimental green roof trays have been installed and instrumented to monitor climatic and hydrological data for a period of one year. These trays consisted of different configurations, including unplanted ballast stone over bark mulch tray (control tray, replicating an existing 4 m2 tray on the nearby Auckland Library green roof) and six planted trays, two of 'Eco-pillow' trays (a proprietary, lightweight system of pre-grown pillows over moisture retention materials replicating an existing 4 m2 tray on the nearby Auckland Library green roof), two trays with ~150 mm depth of conventional green roof media and drainage mat (Daltons living roof mix), and two trays with ~150 mm depth of an experimental green roof media (Daltons pine grow mix). The conventional media met the Auckland Council specifications for green roof media for stormwater management, TR2013/045. Native Plant species selected by the local Iwi, Ngāti Whātua Ōrākei, include one succulent (Disphyma australe) herbs, sedges, rushes, and woody shrubs up to 1 m height with no sedums established. Hydrology monitoring measures runoff and peak discharge reduction in rainfall events by comparing precipitation and runoff depths using calibrated pressure transducers and custom orifice tubes. This paper discusses preliminary results that suggest that all trays have comparable performance in averaged runoff volume and peak discharge reduction ranging between 83% and 93%, and 96% and 98%, respectively, under a daily irrigation regime. It is envisaged that the insights from this ongoing study will drive the broader adoption of green roofs, supporting their widespread implementation across Auckland and New Zealand.

DOI: https://doi.org/10.64697/978-90-835589-7-4_41WC-P1870-cd

Year: 2025