Influence of water storage and plant crop factor on green roof retention and plant drought stress

What is it about?

Green roofs are a unique urban ecosystem which have potential to mitigate stormwater runoff and compensate for loss of natural vegetation in cities. While green roofs have great potential to reduce stormwater runoff, their rainfall retention is highly variable due to differences in green roof configuration. Substrate depth, species selection and plant density are considered the most important drivers of green roof rainfall retention. Therefore, appropriate substrate depth, and plant selection is critical to ensure maximum rainfall retention, plant survival and maintenance of plant coverage. While increased substrate depth increases retention via increased water storage capacity, there is a trade-off with weight as substrate depth is nearly always limited by the weight-loading capacity of buildings, particularly in retrofit situations. Hence, it is important to minimize depth without limiting the amount of water available for plants or reducing rainfall retention. Plants are an important determinant of ET, the main process of storage regeneration between rainfall events, and hence retention. Some non-succulents (such as mono-cots, woody, and herbaceous species) show a combination of high ET and high drought resistance in their natural habitats and are likely to maximize rainfall retention and survival. Ideal green roof configuration in hot and dry climates, when planted with a higher water-using species would reduce stormwater runoff after rainfall events and when planted in the optimal substrate depth would also survive periods of water-deficit between rainfall events.

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Photo by Thomas Kinto on Unsplash

Photo by Thomas Kinto on Unsplash