Abstract
The runoff retention effectiveness of 10 extensive green roof (EGR) modules (100 mm substrate planted Sedum lineare Thunb.) were analyzed in Beijing for 22 rainfall events (2.4–46.4 mm) from 1 July to 30 September 2017. Differences between minimum inter-event dry periods, module scales, substrate hydraulic conductivity and depths, drainage layer types and rainfall characteristics were examined to study their correlation to the retention performance of EGRs. In general, EGRs with lower substrate hydraulic conductivity, deeper substrate and lower rainfall depth had higher runoff retention performance. By comparsion, no siginificant correlation was found between rainfall duration, prior dry period, average rainfall intensity, drainage layer type and EGR runoff retention rate. Analyses of variance (ANOVA) and Tukey tests supported these results. Low or moderate rainfall (<15 mm) may or may not have an effect, but heavy rainfall (>25 mm) definitely affects the EGR retention performance of the next rainfall event.
Highlights
In the process of rapid urbanization, cities’ impervious surface areas have rapidly increased.Urban local flooding caused by rainwater has severely affected the aquatic urban environment.Many cities in China have experienced flood events and suffered heavy property and human life losses [1]
The results provided information on the extent to which these factors are related to the runoff retention performance of green roofs, as a guide to the construction of the green roof in practical projects
The duration of the monitored rainfall events ranged between 10 min to 3793 min when using the 24-h
Summary
Many cities in China have experienced flood events and suffered heavy property and human life losses [1]. 30 cities in China have started pilot construction of ‘sponge cities’ and many low-impact developments (LID) facilities have been constructed to alleviate urban local flooding problems [2]. The ‘green roof’ is one of the typical forms of LID systems in sponge cities, regulating both quantity and quality of rainfall runoff [3]. Known as the ‘fifth façade’ of the building, have always been virgin land in the city yet to be reclaimed, and are often ignored or forgotten. Compared with other LIDs, green roofs control rainfall runoff without taking up extra urban land, and provide good thermal insulation and significant energy-saving abilities [4,5]
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