Climate change is beginning to take its toll worldwide. The ramifications of intense and out of season rainfall over high-density urban areas has resulted in distress to our communities and damage to our environments. Instances of urban flooding have been seen recently in North America, but are also becoming more frequent here in Australia.

As a result of increasing urbanisation, permeable surfaces that allow water to freely drain have been replaced by unyielding surfaces that give water no place to evacuate during heavy rainfall. What’s worse is that these rigid surfaces funnel rapidly draining water toward already under-pressure stormwater and sewerage systems that often become clogged with debris.

Many urban centres in Australia are aware that an overhaul of existing stormwater and sewerage systems is needed, but what if we could aid these systems by providing additional water catchment areas in the form of green roofs?

With rising climates linked to increased rainfall globally, green roofs can be retrofitted to existing infrastructure or incorporated into future designs for increased sustainability and viability of our cities. Green roofs can also complement other green infrastructure technologies, such as permeable pavements, bioswales, cisterns and green roofs, to meet the challenges of extreme weather events in tandem.

Not only do green roofs allow us to bring natural aesthetic to our urban environments in the form of plantlife, a recent study completed by University of Toronto civil engineer Jenny Hill and co-researchers at the school’s Green Roof Innovation Testing Lab (GRIT Lab), showed that green roofs have the capacity to capture an average of 70 per cent of rainfall over a given time.

This capacity is dependent on a range of variables, such as the growing media incorporated into the roof, whether or not the roof had been sufficiently watered prior to the rainfall, and the type of irrigation schedules the roof had in place.

While further research is required to determine how best to mitigate storm-water retention across a wide-range of green roof designs, sizes, and incorporated plantlife; the study is promising in that it provides another frontier for which green infrastructure can help cities to design for emerging climate challenges.

More information on the study methods and outcomes can be found HERE