Storm water retention and actual evapotranspiration performances of experimental green roofs in French oceanic climate

Abstract

Green roofs are promising urban management tools from the standpoint of both rainwater management and microclimatology. They are considered as a storm water mitigation technique and may also favour evapotranspiration fluxes, which can be beneficial for urban comfort during summer periods. In France, however, water retention performance of green roofs remains unknown, and published values are often unsuitable. Six experimental roofs, including two thicknesses of growing media, three types of vegetation cover and bare surfaces, were monitored for two years in Nantes and compared to an experimental gravel flat roof. The thickest media combined with the most densely vegetated cover yields the best results in terms of storm water mitigation and actual evapotranspiration. In winter, the rainwater retention performance is clearly dependent on the type of experimental roof vegetation. This kind of experimental set-up is well suited to assisting urban planners design tools for storm water mitigation in buildings.

Keywords:

• green roofs
• storm water retention
• runoff
• evapotranspiration

Acknowledgement

The authors would like to express their thanks to France’s National Research Foundation (ANR) for sponsoring this study under contract ANR-09-VILL-0007 (VegDUD). Our gratitude is also extended to the CRITT Horticole and ONERA organisations for their collaboration, in addition to the entire technical staff at CSTB.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was sponsored by France’s National Research Foundation (ANR) under contract ANR-09-VILL-0007 (VegDUD).