Factors Affecting Runoff Retention Performance of Extensive Green Roofs

Gong, Ya Dong; Yin, Dingkun; Fang, Xing; Li, Junqi

doi:10.3390/w10091217

Cited by 34 publications

(19 citation statements)

References 27 publications

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“…Generally, the depth of precipitation event influences rainfall retention rate expressed as the percentage of rainfall retained within green roofs. In their research Gong et al reported an investigation conducted in Beijing for 22 rainfall events with use of 10 green roof modules in which lower values of stormwater retention rate were obtained in the case of heavy rains, while high retention rates were observed in the case of small storms [Gong et al, 2018]. Similar results were obtained by Burszta-Adamiak in the research conducted in Wrocław.…”

Section: Resultssupporting

confidence: 53%

“…On the basis of the results from the studies available in the literature, it can be expected that the relationship between ADP and (P r ) would be much weaker if all natural rainfalls were included in the analysis regardless of their size (even those that did not cause runoff). In their research, Gong et al took into account all precipitations (including light rains that do not caused the runoff) and they established that the antecedent dry periods up to 14 days had little effect on runoff retention [Gong et al, 2018]. Schulz et al found that the retention for individual rain events showed a strong dependence on both the length of ADP and the size of the event [Schultz et al 2018].…”

Section: Resultsmentioning

confidence: 99%

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Influence of the Hydrogel Amendment on the Water Retention Capacity of Extensive Green Roof Models

et al. 2020

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The goal of the research was to investigate the retention capacity of six green roof models (SHP1, SHP2, SHP3, SH, S, and SP) constructed with the use of the square-shaped plastic trays, Floradrain FD 25 drainage elements, SF filter sheets, and the specified extensive substrates (with or without the hydrogel amendment). The SHP1 and SHP2 models were constructed in March 2017, SHP3 and SHin November 2017, while S and SPin April 2018. Four models (SHP1, SHP2, SHP3, and SP) contained the plants (the goldmoss stonecrop Sedum Acre), whereas two models (S and SH) did not contain the vegetation. The substrates of SHP1, SHP2, SHP3, and SH models contained the hydrogel admixtures. The investigations were conducted with the use of simulated (and partially natural) precipitations. The water retention capacity of each green roof model was established based on the difference between the precipitation volume and the volume of runoff from a model. The results show that green roofs can be useful stormwater management tools. The calculated stormwater retention rates ranged from 29.50% to 85.15%. In most cases, the best water retention capacity was exhibited by the SHP3 model, constructed in November 2017 and planted in April 2018, containing the substrate amended with superabsorbent (cross-linked potassium polyacrylate). The similarly constructed SHP1 and SHP2 models, which were built in March 2017, in some cases had lower water retention capacity. These models contained older hydrogel and were overgrown with older, smaller, and worse looking plants, partially supplanted by mosses. Such results indicate that the efficiency of hydrogel may decrease over time. In many cases, the S (not vegetated, without hydrogel), SH (not vegetated, with substrate containing hydrogel), and SP (vegetated, without hydrogel) models had slightly lower water retention capacity. The results of investigations indicate that there was a relatively strong positive linear correlation between the retention depth and duration of the antecedent period elapsed from the preceding total (or substantial) saturation of the green roof models (labelled in this article as period since total saturation-PSTS). The weather conditions i.e. air temperature and relative humidity as well as PSTS are very important parameters that influence the retention capacity of the green roof models. The result show that duration of PSTS can be stronger correlated with the retention depth than antecedent dry period (ADP) elapsed from the end of last precipitation, regardless of its depth and intensity.

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Section: Resultssupporting

confidence: 53%

Section: Resultsmentioning

confidence: 99%

Influence of the Hydrogel Amendment on the Water Retention Capacity of Extensive Green Roof Models

et al. 2020

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“…Gong et al 3 studied the flow retention effectiveness of green roof modules and concluded that heavy rains (>25mm) significantly affect there tention performance of extensive greenroofs in then extrainyevent.…”

Section: Introductionmentioning

confidence: 99%

Water balance study on green roof in Brazil

Calheiros¹,

Gonçalves²,

Silva³

et al. 2020

IJH

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The present study aims to investigate the water balance in conventional and green roofs and also to monitor the development of peanut grass (Arachis repens Handro), relating the type of vegetation cover or not with its water retention capacity and, consequently, to obtain the coefficient of runoff for each scenario tested. The scenarios tested were: (1) conventional collection surface with fiber cement tile, (2) green roof structure with substrate and no plant, and (3) planted green roof. The rains incident on the roof were obtained for the city of Itajubá, in Minas Gerais, by the curve of i-d-f with 5min of duration and 5years of return period according to the recommendation of NBR 10844 (ABNT,1989). The volumes of storm water runoff and drained from the bottom of the roofs studied were collected in calibrated graduated containers. It was concluded that: the peanut grass showed satisfactory development and high recovery capacity; the peanut grass took only 1½ month to cover the entire roof; the coefficient of runoff of the green roof for intense rainy season was on average 0.569 and in the dry season it was 0.003. While the conventional roof presented average surface runoff coefficient of 0.995 for the rainy season and 0.901 for the dry season; the component of the green roof that contributed most to the rainwater retention was the substrate. Therefore, attention should be paid to the choice of substrate so that it can adequately grow the plant, retain rainwater and not contaminate the bottom drainage water of the roof that can be used for less noble uses.

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“…The retention and interception ability of GRs on rainwater runoff is affected by several factors, such as the type and material of the substrate layer [9,10], substrate layer thickness [11], GR scale [12], vegetation type [13][14][15], rainfall time [16], rainfall depth [17], type of drainage layer [18], water storage, whether the layer is set or not, and roof slope. Through a large number of experiments and simulation results, it can be concluded that rainfall depth as well as substrate layer thickness and material type are important parameters affecting the retention and interception capacity of the rainwater runoff of GRs.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on the Retention and Interception Effect of an Extensive Green Roof (GR) with a Substrate Layer Modified with Kaolin

Liu

Cai

et al. 2020

Water

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Extensive green roofs (GRs) often appear as pollution sources during actual rainfall events; therefore, it is necessary to study the control of nutrient leaching in the substrate layer. In this study, four extensive GR experimental devices are built: two with artificial granular structure substrate layers improved with kaolin as a binder, one with a commercial substrate layer, and one with a standard roof (SR). Based on the simulated rainfall conditions in different local recurrence periods, the delayed outflow time, rainfall retention rate, event mean concentration (EMC), and cumulative pollutant quality of NH4+, NO3−, NO2−, and PO43− in the effluents were measured and evaluated. The results of the study indicate that under simulated rainfall in all the experimental design recurrence periods, the kaolin-modified substrate layer does not exhibit a more significant retention capacity than the commercial substrate. However, it does show some suppression of the leaching effect of NO3− and PO43− in the runoff. The reduction rate of cumulative NO3− quality is 6.56%, and PO43− is 10.54%. In future practical engineering and related research, attention should be paid to the influence of the type and addition amount of the substrate layer modifier on the stability of the granular structure to prevent nutrient loss caused by soil erosion.

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Factors Affecting Runoff Retention Performance of Extensive Green Roofs

Cited by 34 publications

References 27 publications

Influence of the Hydrogel Amendment on the Water Retention Capacity of Extensive Green Roof Models

Influence of the Hydrogel Amendment on the Water Retention Capacity of Extensive Green Roof Models

Water balance study on green roof in Brazil

Experimental Study on the Retention and Interception Effect of an Extensive Green Roof (GR) with a Substrate Layer Modified with Kaolin

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