Green roofs: Effects of plant species used on runoff

Abstract

Green roofs are becoming a major nature‐based solution worldwide to reduce urban stormwater runoff. Runoff reduction and retention mainly depend on the hydrological characteristics of substrates and the water use strategies of plants. However, little is known about how plant species affect the hydrological performance of green roofs. Two commonly used succulent plants and four turfgrass species were investigated for their impacts on the hydrological performance and runoff reduction of green roof lysimeters under controlled conditions using a rainfall simulator. The results showed that two succulent plants (Sedum lineare and Callisia repens) did not make significant contributions to canopy interception in any of the four seasons and made only minor contributions to evapotranspiration (ET) water loss in autumn and winter, resulting in minor effects on runoff reduction by the green roofs. Festuca arundinacea contributed 47.4–116.7% of water loss via transpiration and 36.5% of runoff reduction under a 25 mm day−1 rainfall intensity in spring and 48.0% of runoff reduction under a 10 mm day−1 rainfall intensity in winter. Poa pratensis, Lolium perenne, and Agrostis stolonifera also significantly reduced runoff. Runoff reductions by extensive green roofs were mainly caused by ET rather than by their canopy interceptions. Plant shoot biomass and ET were the primary factors controlling the runoff reduction by extensive green roofs. Our results strongly suggest that the runoff reduction capacity of extensive green roofs can be greatly improved by selecting plant species with a higher shoot biomass and ET rate.

Water Resilience by Centipedegrass Green Roof: A Case Study

“…Speak et al [32] found that turfgrass species were more effective at PM10 capture than sedums. Our previous study also found that turfgrass species performed better in runoff reduction than sedums [9].…”

“…The centipedegrass green roof only performed 47.4% of runoff reduction under the 1487.1 mm of annual precipitation, as seen in Table 1. Runoff reduction could be promoted by the increase of water retention capacity of the green roofs [9]. The field capacity represents the maximum rainwater retention of the green roof.…”

“…③The measurement of evapotranspiration (ET) was performed according to our previous study [9]. The mass of the green roof plot was recorded daily and the mass changes represent the water loss by ET of the green roofs.…”

“…The weight of plant was evaluated by seasonal samplings from a monitored column in the experimental plots. 3 The measurement of evapotranspiration (ET) was performed according to our previous study [9]. The mass of the green roof plot was recorded daily and the mass changes represent the water loss by ET of the green roofs.…”

“…Nature-based solutions (NBS) use nature and ecosystem services to provide social, economic, and environmental benefits [4,5]. One NBS is a green roof, which could provide benefits of stormwater management and urban heat mitigation [6][7][8] without occupying precious and highly competitive land at ground level [9]. Benefits of green roofs are mainly achieved by the performance of plants; however, the shallow substrates with limited availability of water and nutrients present a great challenge for the growth and survival of green roof plants [10,11].…”