scholarly journals Water Resilience by Centipedegrass Green Roof: A Case Study

Buildings ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 141 ◽  
Author(s):  
Shuai Hu ◽  
Lijiao Liu ◽  
Junjun Cao ◽  
Nan Chen ◽  
Zhaolong Wang
Keyword(s):  
Soil Moisture ◽  
Green Roof ◽  
Green Roofs ◽  
Saturated Soil ◽  
Water Retention Capacity ◽  
Water Runoff ◽  
Retention Capacity ◽  
Runoff Reduction ◽  
Eremochloa Ophiuroides ◽  
Rain Events

Centipedegrass (Eremochloa ophiuroides) is a low-maintenance turfgrass. The first extensive green roof of centipedegrass was established in TongZhou Civil Squares in 2014. However, storm-water-runoff reduction, water-retention capacity, and plant-water requirements by a centipedegrass green roof has not yet been defined. The soil moisture dynamics, rainwater-retention capacity, runoff reduction, and plant evapotranspiration were investigated by simulated centipedegrass green roof plots, which were constructed in the same manner as the green roofs in TongZhou Civil Squares in 2018. The results showed that the centipedegrass green roof retained 705.54 mm of rainwater, which consisted 47.4% of runoff reduction. The saturated soil moisture was 33.4 ± 0.6%; the excess rainfall over the saturated soil moisture resulted in runoff. The capacity of rainwater retention was negatively related to the soil moisture before rain events and was driven by plant evapotranspiration. Drought symptoms only occurred three times over the course of a year when the soil moisture dropped down to 10.97%. Our results indicate that the rainwater retained in the soil almost met the needs of plant consumption; a further increase of rainwater retention capacity might achieve an irrigation-free design in a centipedegrass green roof.

scholarly journals Water balance study on green roof in Brazil

2020 ◽  
Vol 4 (4) ◽  
pp. 141-144
Author(s):  
Calheiros Herlane Costa ◽  
Silva Fernanda Gomes Gonçalves ◽  
Costa Luisa Silva ◽  
Silva Matheus Lins Macedo
Keyword(s):  
Water Balance ◽  
Rainy Season ◽  
Green Roof ◽  
Green Roofs ◽  
Dry Season ◽  
Water Retention Capacity ◽  
Water Runoff ◽  
Retention Capacity ◽  
Balance Study ◽  
Recovery Capacity

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.

scholarly journals Evapotranspiration Measurement and Estimation of Crop Coefficient for Native Plant Species of Green Roof in the Tropics

Water ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1669
Author(s):  
Ming Fai Chow ◽  
Muhammad Fadhlullah Abu Bakar ◽  
Jee Khai Wong ◽  
Lloyd Ling
Keyword(s):  
Soil Moisture ◽  
Plant Species ◽  
Green Roof ◽  
Crop Coefficient ◽  
Green Roofs ◽  
P Value ◽  
Water Retention Capacity ◽  
Native Plant ◽  
Retention Capacity ◽  
Native Plant Species

Extensive green roof is one of the sustainable urban stormwater management alternatives to manage and mitigate the urban surface runoff. In order to implement green roofs more effectively, suitable plant species and substrate components for tropical climate must be identified. The aim of this study is to investigate the evapotranspiration (ET) behaviors in extensive green roofs based on different substrate types and local native plant species. Four green roof test beds containing pro-mixing pot and burn soils were each vegetated with Axonopus Compressus (grass) and Portulaca Grandiflora (sedum). A weather station with soil moisture sensors was installed to measure the weather and soil moisture data. The results showed that the mean ET rates for grass-pot soil, sedum-pot soil, grass-burn soil and sedum-burn soil were 1.32 ± 0.41 mm/day, 2.31 ± 0.72 mm/day, 1.47 ± 0.39 mm/day and 2.31 ± 0.43 mm/day, respectively. It is noted that environmental parameters such as ambient temperature, solar radiation and wind speed showed significantly positive relationship (p value < 0.01) with ET rates of green roofs except relative humidity. The crop coefficients (Ks) for the studied green roof plant species are estimated based on actual and reference evapotranspiration rates. The sedum planted in burn soil showed the highest crop coefficient (0.64), followed by sedum in pot soil (0.62), grass in burn soil (0.39) and grass in pot soils (0.37), respectively. The findings in this study also showed that substrate with better water retention capacity generally improved the Ks values.

scholarly journals Phosphorus and Metals Leaching from Green Roof Substrates and Aggregates Used in Their Composition

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 112 ◽  
Author(s):  
Agnieszka Karczmarczyk ◽  
Anna Baryła ◽  
Joanna Fronczyk ◽  
Agnieszka Bus ◽  
Józef Mosiej
Keyword(s):  
Heavy Metals ◽  
Green Roof ◽  
Green Roofs ◽  
Point Of View ◽  
Water Retention Capacity ◽  
Retention Capacity ◽  
Batch Tests ◽  
Quality Literature ◽  
Materials Used ◽  
Runoff Quality

Green roofs are constructions made of different layers, each serving a dedicated function. Substrates and materials used in their composition are essential from the point of view of rainwater retention and plant development, but they may have an adverse effect on runoff quality. Literature studies show that phosphorus and heavy metals are of main importance. The total roofs area covered with green increased in the last years in cities as they are efficient in retention of rainwater and delaying of the runoff, therefore, protecting the cities against floods. As green roofs filtrate a significant amount of rainwater, materials used in substrates composition should be carefully selected to protect urban receivers against pollution. The aim of this study was to assess phosphorus and heavy metals leaching from different green roof substrates and their components with the focus on green roof runoff quality. Both commercially made green roof substrates and often used compounds (construction aggregates) were tested in laboratory batch tests for P, Cu, Ni, Cd, and Zn content in extracts. Based on the results of this study, it could be emphasized that a large part of commonly used construction aggregates can be a source of phosphorus, some also can release elevated values of nickel. Therefore, the materials should be carefully tested before use in the green roof substrate composition, not only for their physical properties reflecting water retention capacity, but also for chemical composition.

scholarly journals Analysis of roof greening technology impact on rain and meltwater retention

2020 ◽  
Vol 175 ◽  
pp. 11023
Author(s):  
Elena Sysoeva ◽  
Margarita Gelmanova
Keyword(s):  
High Efficiency ◽  
Green Roof ◽  
Experimental Studies ◽  
Green Roofs ◽  
Climatic Conditions ◽  
Water Runoff ◽  
Substrate Thickness ◽  
Runoff Reduction ◽  
The Usa ◽  
Analytical Review

Over the past 20 years, a large number of studies have been published on reducing storm runoff by various types of green roofs. This article analyzes the results of experimental studies presented in 39 publications on green roof runoff reduction in a climate similar to the climate of Russia: in Canada, the USA, Finland, Norway, France. An analytical review found that the ability of green roofs to retain rainfall varies from 20 to 99.5% depending on climatic conditions (duration and intensity of rains, duration of dry periods, solar radiation, temperature and humidity, wind conditions), the properties of green roof layers (moisture capacity of the substrate and a drainage layer, the substrate thickness), the type of vegetation, the geometry of a green roof (slope and orientation). Green roofs can be a useful tool for reducing urban storm water runoff. However, in order to ensure high efficiency, it is necessary to use green roof technology with other measures to reduce runoff.

Innovative green roof with high water retention and durability

2019 ◽  
Author(s):  
Thomas Cornelius Buch-Hanser ◽  
Guangli Du ◽  
David John Duffus
Keyword(s):  
Water Retention ◽  
Green Roof ◽  
Water Reservoir ◽  
Green Roofs ◽  
High Water ◽  
Water Retention Capacity ◽  
Storm Events ◽  
Concrete Element ◽  
Retention Capacity ◽  
Roof System

<p>Given the rapid increase in urban populations, combined with the effects of climate change, cities are struggling to provide green spaces to address liveability as well as adaptability to new challenges. Water retention and bio-diversity are the main advantages of green roofs. There are, however, limitations to green roofs that impede their acceptance and proliferation. There is for example uncertainty on how much water they retain during major storm events. In terms of building technology, green roofs today aren’t robust, and the risk for leakage through the roof membrane is disproportionally high when compared to the cost. A newly developed innovative green roof system with high water retention capacity and high durability will be presented. The patented prefabricated technology incorporate insulation and membrane into a single concrete element, ensuring improved robustness, quickened building times and a long term durable product. Initial indications for pricing indicate that the system is price-neutral when compared with green roofs as they are built today. The optimized structural performance obtain same loadbearing capacity, as existing systems, in spite of the relatively increased space created for water reservoir, without compromising the insulation capacity, hence the new green roof system further contribute to increased sustainability.</p>

scholarly journals Analysis of the retention capacity of green roofs

2012 ◽  
Vol 16 (1) ◽  
pp. 3-9 ◽  
Author(s):  
Ewa Burszta-Adamiak
Keyword(s):  
Urban Areas ◽  
Soil Surface ◽  
Green Roofs ◽  
Retention Capacity ◽  
Local Conditions ◽  
Rainfall Events ◽  
Runoff Reduction ◽  
Education Centre ◽  
Peak Runoff ◽  
Rain Events

Abstract Green roofs are one of the modern solutions used to achieve sustainable stormwater management in urban areas. These structures are still more often designed for newly constructed buildings in Poland, based on the observations of changes in urban areas that result in the increased sealing of soil surface and thus in the limitation of natural stormwater infiltration and retention sites. In spite of a growing interest in green roofs, the data related to their retention capacity in Polish conditions is still insufficient. This study presents the results of the author’s tests, conducted in the years 2009-2010 on experimental sites located on the roof of the Science and Education Centre building of the University of Environmental and Life Sciences in Wrocław. The aim of these tests was to determine the retention capabilities of green roofs and the runoff delay and peak runoff reduction during rainfall events recorded in local conditions. The results show that green roofs can play a significant role in the reduction of total outflow volume of stormwater falling on their surface. Multi-layered structure of green roofs contribute also to a slowdown in the outflow of stormwater and to reduction in the peak runoff volume in comparison to the maximum recorded intensity of rainfall. Mean retention for 153 analysed rainfall events amounted from 82.5% to 85.7% for green roofs. In the case of rain events up to 1 mm a day, the retention for green roofs reached nearly 100%.

scholarly journals Performance of Green Roofs for Rainwater Control

2020 ◽  
Author(s):  
A. Raimondi ◽  
G. Becciu
Keyword(s):  
Goodness Of Fit ◽  
Probabilistic Approach ◽  
Green Roof ◽  
Green Roofs ◽  
Water Retention Capacity ◽  
Retention Capacity ◽  
Climate Conditions ◽  
Average Return ◽  
Roof Design ◽  
The Given

AbstractGreen roofs can be an effective tool for sustainable urban drainage, since they reduce and retain runoff by delaying its peak. Most studies analysing the retention capacity of green roofs are usually referred to a specific place and roof condition and do not consider the possibility that the roof could be partially pre-filled from previous rainfalls at the beginning of the given event. The aim of this paper is to develop an analytical probabilistic approach to evaluate green roof performance for stormwater control in terms of runoff that could be applied for different sites and climate conditions. To this end, the possibility that the green roof retention capacity could not be completely available owing to pre-filling from previous rainfall events has been considered and equations for an optimum green roof design, relating the runoff average return interval to the water retention capacity, have been proposed. The influence of parameters affecting the runoff process has been examined in depth and a case study to test the goodness of fit of the resulting equations has been developed.

scholarly journals Impact of the Hydrogel Amendment and the Dry Period Duration on the Green Roof Retention Capacity

2020 ◽  
Vol 27 (3) ◽  
pp. 357-371
Author(s):  
Iwona Deska ◽  
Maciej Mrowiec ◽  
Ewa Ociepa ◽  
Michał Michniewski
Keyword(s):  
Urban Areas ◽  
Water Retention ◽  
Drainage Basin ◽  
Green Roof ◽  
Green Roofs ◽  
Water Retention Capacity ◽  
Retention Capacity ◽  
Rainwater Infiltration ◽  
Basin Surface ◽  
Significant Difference

AbstractClimate changes as well as the urbanisation and economic development influence the characteristics of the stormwater runoff in the cities. The sealing of drainage basin surface leads to an increase of the runoff intensity, thereby decreasing the rainwater infiltration. This situation can lead to the risk of flooding in urban areas. Therefore, especially in great cities there is a need for application of such solutions that will support the operation of the sewage systems. The examples of such solutions are, among others, the green roofs. The paper presents the results of investigation of the water retention capacity of 4 green roof models containing following growing media: (1) the typical green roof substrate without any amendments, (2) the substrate with addition of about 1 % by weight of hydrogel (the cross-linked potassium polyacrylate), (3) the substrate containing about 0.25 % by weight of hydrogel, (4) the substrate with addition of expanded clay and perlite. The models were not vegetated in order to investigate only the water retention capacity of drainage elements and substrates. The water retention capacity of green roof models was investigated in the laboratory conditions with use of artificial precipitations simulated after diverse antecedent dry weather periods (ADWP) amounting to: 1, 2, 5, 7, and 12 days. The intensities of artificial precipitations were relatively high and ranged from 1.14 to 1.27 mm/min, whereas their durations ranged from 7.75 to 12.56 min. These values of intensities and durations corresponded to the design rainfall intensities calculated using Blaszczyk’s equation for annual rain depth equal to 600 mm and the return periods ranged from 5 to 15 years. The obtained results indicate that the water retention capacity of green roof models, expressed as the volumes (or depths) of rainwater retained within their structures, increases with an increase of ADWP. Results indicate that the relation between ADWP and the amount of water retained in the layers of green roofs in the case of relatively short antecedent dry weather periods provided for the analysis (from 1 to 7 days) may be approximately linear. The results of the one-way ANOVA indicate that in the case of all models there is a statistically significant difference between the values of retention depth for specified ADWP (p < 0.001). During more than half of simulated precipitations, especially in the case of longer ADWPs lasting 5, 7, and 12 days the best water retention capacity had Model 3, with substrate containing about 0.25 % by weight of hydrogel. On the other hand, the results show that the weakest retention capacity had Model 2 (with substrate containing 1 % by weight of hydrogel). In the case of longer ADWPs (lasting 7 and 12 days) relatively weak water retention capacity had Model 4 (with substrate containing the addition of expanded clay and perlite). It can be concluded that too large amount of hydrogel added to the substrate can have an unfavourable impact on the water retention capacity of green roofs.

scholarly journals Drainage flux simulation of green roofs under wet conditions

2018 ◽  
Vol 49 (4) ◽  
pp. 242-252 ◽  
Author(s):  
Francesco Bettella ◽  
Vincenzo D'Agostino ◽  
Lucia Bortolini
Keyword(s):  
Water Retention ◽  
Green Roof ◽  
Green Roofs ◽  
Water Retention Capacity ◽  
Growth Media ◽  
Initial Water Content ◽  
Retention Capacity ◽  
Worst Case ◽  
Steady State Condition ◽  
Growing Medium

The role of green roofs in reducing drainage fluxes is known, but despite extensive analysis in the literature, methods to predict the hydrologic performance for a given green roof composition are scarce. These methods are useful for the hydraulic design and for planning regulations that impose specific hydrological responses. This research investigates on the prediction of the drainage fluxes produced below a green roof with initial water content equal to its water retention capacity (worst-case scenario). Laboratory tests were performed to analyse the rainfall-drainage relationship for green-roof and single components (growing media and drainage storage layers) under specific rainfall intensities. Two types of largely used drainage/storage layers and growth media were analysed, both singularly and in combination. The experiments consider two rainfall events lasting 10 min with constant intensity. The results indicate that the Curve Number (CN) method (U.S. Soil Conservation Service) with a simple adaptation can be used to reproduce the green-roof hydrologic behaviour under antecedent moisture conditions comparable with those of the experiments. In fact, the water retention capacity, controlling the water-output initiation below the green roof, can be used as threshold variable of a step function, above which the CN method is applicable and below which drainage fluxes are practically null. Through this position, the CN assignment for a composite greenroof can be consistently estimated using the proprieties of the single components (drainage/storage layer and growing medium) and it provides values that are very close to those of waterproof media and quite higher than those suggested in companion researches. Drainage amounts are predicted with a standard error equal to 1.50 mm, which corresponds to 5.7% of the mean value observed. After rain initiation, the steady state condition of the drainage flux has proved to be markedly affected by the growing medium and drainage layer composing the system, which result effective in discriminating the green roof performance.

scholarly journals The rainwater retention mechanisms in extensive green roofs with ten different structural configurations

2021 ◽  
Author(s):  
Jun Wang ◽  
Ankit Garg ◽  
Shan Huang ◽  
Guoxiong Mei ◽  
Jiaqin Liu ◽  
...  
Keyword(s):  
Green Roof ◽  
Water Storage ◽  
Single Layer ◽  
Green Roofs ◽  
Layered Soil ◽  
Retention Capacity ◽  
Drainage Layers ◽  
Structural Configurations ◽  
Large Water ◽  
Rain Events

Abstract Rainfall infiltration, rainwater retention, runoff and evapotranspiration (ET) are important components of the water balance in green roofs. These components are expected to be influenced by variations in the structural configurations (i.e., substrate layers) of green roofs. This study explores the influence of layered soil and green roof configurations on the rainwater retention capacity (RRC) of the roofs as compared to conventional improvements (i.e., soil conditioning and enhanced substrate depth). Ten different extensive green roof modules were designed by varying the substrate materials, substrate depths, storage/drainage layers and vegetation layers. For all modules, the RRCs ranged from 34 to 59%. The RRCs of layered-soil were 1–4% higher than that for single-layer soil. The RRC increased by 13% in the presence of a water storage module. It can be concluded that highest RRC corresponds to a combination of high-permeability soil in the upper layer along with a relatively large water holding capacity in the deep layer. Water storage layer and layered soil could significantly delay the water stress in vegetation. The importance of wick irrigation, vegetation types, back-to-back rain events and the ET rate on the RRC were also discussed.

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