scholarly journals Investigation of the Influence of Hydrogel Amendment on the Retention Capacities of Green Roofs

2018 ◽  
Vol 25 (3) ◽  
pp. 373-382 ◽  
Author(s):  
Iwona Deska ◽  
Maciej Mrowiec ◽  
Ewa Ociepa ◽  
Katarzyna Łacisz
Keyword(s):  
Urban Areas ◽  
Drainage Basin ◽  
Green Roof ◽  
Green Roofs ◽  
Retention Capacity ◽  
Rainwater Infiltration ◽  
Sewer Systems ◽  
Basin Surface ◽  
Drainage Layers ◽  
Antecedent Dry Days

Abstract Progressive economic development as well as urbanisation influence the characteristics of the stormwater runoff. Progressive sealing of drainage basin surface prompts the decrease of rainwater infiltration, thus increasing the runoff intensity. This results in an increase of flood risk. Thus, in urban areas the sustainable urban drainage systems (SUDS) are used in addition to the traditional sewer systems. The examples of SUDS strategy are, inter alia, the roofs covered with vegetation (the green roofs). The paper presents the results of research of retention capacities of 4 diverse green roof models with following growing media: (1) the typical green roof substrate without any additions, (2) the substrate with addition of about 1 % by weight of hydrogel (the cross-linked potassium polyacrylate), (3) the substrate with addition of about 0.25 % by weight of hydrogel, (4) the substrate with addition of expanded clay and perlite. The models did not have the vegetation layers in order to explore only the retention capacities of drainage layers and substrates. The aim of the first part of research was to investigate the retention capacities of green roof models after 1, 2, 6, 8 and 10 antecedent dry days. In the case of 1 and 2 antecedent dry days the best medium retention capacity had green roof model 2 (with substrate with addition of 1 % by weight of hydrogel), and the weakest medium retention capacity had green roof model 1 (without any additions). In the cases of precipitations which occurred after 6 as well as 8 and 10 antecedent dry days the best retention capacity had green roof model 3 (with addition of about 0.25 % by weight of hydrogel). The weakest retention capacity had in these cases green roof model 4 (with addition of expanded clay and perlite). The aim of the second part of research described in the paper was to investigate the retention capacities of green roof models during precipitations that occurred after long antecedent dry periods of time (34, 59 and 106 antecedent dry days). The substrates and drainage layers were air-dry directly before precipitations. The best retention capacity had in this case green roof model 3 (with the substrate with addition of about 0.25 % by weight of hydrogel). The second largest retention capacity had model 2 (with the substrate with addition of about 1 % by weight of hydrogel). The definitely weakest retention capacity had model 4 containing the substrate with addition of expanded clay and perlite. The results may indicate that the efficacy of hydrogel decreased over time probably due to its decay under the influence of solar radiation.

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 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.

scholarly journals Addressing the Water–Energy–Food Nexus through Enhanced Green Roof Performance

2021 ◽  
Vol 13 (4) ◽  
pp. 1972
Author(s):  
Jeremy Wright ◽  
Jeremy Lytle ◽  
Devon Santillo ◽  
Luzalen Marcos ◽  
Kristiina Valter Mai
Keyword(s):  
Climate Change ◽  
Performance Optimization ◽  
Urban Areas ◽  
Stormwater Management ◽  
Green Roof ◽  
Green Roofs ◽  
Management Tool ◽  
Contributing Factors ◽  
Rainwater Runoff ◽  
Rain Events

Urban densification and climate change are creating a multitude of issues for cities around the globe. Contributing factors include increased impervious surfaces that result in poor stormwater management, rising urban temperatures, poor air quality, and a lack of available green space. In the context of volatile weather, there are growing concerns regarding the effects of increased intense rainfalls and how they affect highly populated areas. Green roofs are becoming a stormwater management tool, occupying a growing area of urban roof space in many developed cities. In addition to the water-centric approach to the implementation of green roofs, these systems offer a multitude of benefits across the urban water–energy–food nexus. This paper provides insight to green roof systems available that can be utilized as tools to mitigate the effects of climate change in urbanized areas. A new array of green roof testing modules is presented along with research methods employed to address current issues related to food, energy and water performance optimization. Rainwater runoff after three rain events was observed to be reduced commensurate with the presence of a blue roof retention membrane in the testbed, the growing media depth and type, as well as the productive nature of the plants in the testbed. Preliminary observations indicate that more productive green roof systems may have increasingly positive benefits across the water–energy–food nexus in dense urban areas that are vulnerable to climate disruption.

scholarly journals Evaporation from (Blue-)Green Roofs: Assessing the Benefits of a Storage and Capillary Irrigation System Based on Measurements and Modeling

Water ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1253 ◽  
Author(s):  
Dirk Cirkel ◽  
Bernard Voortman ◽  
Thijs van Veen ◽  
Ruud Bartholomeus
Keyword(s):  
Energy Balance ◽  
Urban Areas ◽  
Evaporation Rate ◽  
Climate Adaptation ◽  
Irrigation System ◽  
Green Roof ◽  
Green Roofs ◽  
C3 Plants ◽  
Rapid Decline ◽  
Air Temperatures

Worldwide cities are facing increasing temperatures due to climate change and increasing urban density. Green roofs are promoted as a climate adaptation measure to lower air temperatures and improve comfort in urban areas, especially during intensive dry and warm spells. However, there is much debate on the effectiveness of this measure, because of a lack of fundamental knowledge about evaporation from different green roof systems. In this study, we investigate the water and energy balance of different roof types on a rooftop in Amsterdam, the Netherlands. Based on lysimeter measurements and modeling, we compared the water and energy balance of a conventional green roof with blue-green roofs equipped with a novel storage and capillary irrigation system. The roofs were covered either with Sedum or by grasses and herbs. Our measurements and modeling showed that conventional green roof systems (i.e., a Sedum cover and a few centimeters of substrate) have a low evaporation rate and due to a rapid decline in available moisture, a minor cooling effect. Roofs equipped with a storage and capillary irrigation system showed a remarkably large evaporation rate for Sedum species behaving as C3 plants during hot, dry periods. Covered with grasses and herbs, the evaporation rate was even larger. Precipitation storage and capillary irrigation strongly reduced the number of days with dry-out events. Implementing these systems therefore could lead to better cooling efficiencies in cities.

scholarly journals Vegetation Cover Drives Arthropod Communities in Mediterranean/Subtropical Green Roof Habitats

2018 ◽  
Vol 10 (11) ◽  
pp. 4209 ◽  
Author(s):  
Ibrahim Salman ◽  
Leon Blaustein
Keyword(s):  
Vegetation Cover ◽  
Urban Areas ◽  
Green Roof ◽  
Structural Complexity ◽  
Green Roofs ◽  
Life Forms ◽  
Suitable Habitat ◽  
Positive Effects ◽  
Habitat Template ◽  
Arthropod Abundance

Worldwide, urban areas are expanding both in size and number, which results in a decline in habitats suitable for urban flora and fauna. The construction of urban green features, such as green roofs, may provide suitable habitat patches for many species in urban areas. On green roofs, two approaches have been used to select plants—i.e., matching similar habitat to green roofs (habitat template approach) or identifying plants with suitable traits (plant trait approach). While both approaches may result in suitable habitats for arthropods, how arthropods respond to different combinations of plants is an open question. The aim of this study was to investigate how the structural complexity of different plant forms can affect the abundance and richness of arthropods on green roofs. The experimental design crossed the presence and absence of annuals with three Sedum sediforme (Jacq.) Pau (common name: stonecrops) treatments—i.e., uniformly disrupted Sedum, clumped disrupted Sedum, and no Sedum. We hypothesized that an increased structural diversity due to the coexistence of different life forms of plants on roofs is positively related to the abundance and richness of arthropods. We found that arthropod abundance and richness were positively associated with the percent of vegetation cover and negatively associated with substrate temperature. Neither arthropod abundance nor richness was influenced by the relative moisture of substrate. We also found that arthropod abundance and richness varied by green roof setups (treatments) and by seasonality. Arthropod abundance on green roofs was the highest in treatments with annuals only, while species richness was slightly similar between treatments containing annuals but varied between sampling periods. This study suggests that adding annuals to traditional Sedum roofs has positive effects on arthropods. This finding can support the development of biodiverse cities because most extensive green roofs are inaccessible to the public and can provide undisturbed habitat for several plant and arthropod species.

scholarly journals IMPACT OF GREEN ROOF ON HEATING AND COOLING IN CONTEXT OF DIFFERENT CLIMATIC ZONES IN INDIA

2021 ◽  
pp. 436-440
Author(s):  
Ar. Ankur Bhardwaj ◽  
Dr. Shweta Chaudhary ◽  
Ar.Kirti Varandani
Keyword(s):  
Urban Areas ◽  
Green Roof ◽  
Green Roofs ◽  
Climatic Zones ◽  
Sustainable Living ◽  
Secondary Sources ◽  
Heating And Cooling ◽  
The World ◽  
Depth Study ◽  
Rainwater Runoff

The ecological, social and visual commitments that green roofs can make towards sustainable living in more intensified urban centres are generally recognized around the world. Green roof is one such sustainable methodology, utilization of which causes us in insulating the buildings and, subsequently contributing to better energy proficient execution of the same. Green roofs additionally give environment to various species, lessen the rainwater runoff and better deal with the carbon-dioxide cycle. In spite of these advantages, Green roofs are not as basic an element in India as they are in other European and American urban areas. In this paper an attempt has been made to enhance the advantages of this innovation in India. Green roofs systems looks simple in terms of setting up, but actually very complex in maintaining and achieving sustainability. In depth study of green roofs, historic background, climatic zones, impacts of green roofs on heating and cooling, benefits, problems and opportunities is done with the help of data taken from secondary sources like books, magazines and published literature (articles, journals, conference proceedings) form various e-libraries and other online platforms. KEY WORDS: Heating, Cooling, Green Roof, Sustainability)

scholarly journals Surface temperature analysis of conventional roof and different use forms of the green roof

2019 ◽  
Vol 28 (4) ◽  
pp. 632-640
Author(s):  
Anna Baryła ◽  
Agnieszka Bus ◽  
Agnieszka Karczmarczyk ◽  
Joanna Witkowska-Dobrev
Keyword(s):  
Green Infrastructure ◽  
Urban Areas ◽  
Imaging System ◽  
Plant Cover ◽  
Effective Means ◽  
Green Roof ◽  
Green Roofs ◽  
Temperature Changes ◽  
Urban Heat ◽  
Thermal Imaging System

Increasing urban populations raises a number of problems and risks that are strengthened by observed and projected climate change. An increase in green areas (so-called green infrastructure) has turned out to be an effective means of lowering temperature in the city. Green roofs can be one of the possible measures leading to achieving this aim. The aim of the study was the analysis of temperature changes of different roof surfaces (conventional roof, board, intensive roof substrate without plant cover, substrate covered with plants (shrubs). Studies on comparing the temperature between a conventional roof and green roofs were carried out in the period from April to September 2015 on the roof of the building of the Faculty of Modern Languages, University of Warsaw. The measurement was performed using the FLIR SC620 thermal imaging system. As a result of the tests, it was found that in the summer months the differences between the temperature of the green roof and the conventional roof amounted to a maximum of 31.3°C. The obtained results showed that the roof with vegetation can signifi cantly contribute to the mitigation of the urban heat island phenomenon in urban areas during summer periods.

scholarly journals A review of green roof incentives as motivators for the expansion of green infrastructure in European cities

2019 ◽  
Vol 28 (4) ◽  
pp. 641-652 ◽  
Author(s):  
Ewa Burszta-Adamiak ◽  
Wiesław Fiałkiewicz
Keyword(s):  
Green Infrastructure ◽  
Urban Areas ◽  
Financial Incentives ◽  
Large Scale ◽  
Green Roof ◽  
Green Roofs ◽  
Negative Effects ◽  
European Cities

Nowadays green roofs play a key role in alleviating the negative effects of urbanization. Despite investors awareness of the advantages of green roofs, there are still some barriers that hinder investments on a large scale. As a result a financial and non-financial incentives are implemented. The review presented in this paper allowed to identify the most popular initiatives and to formulate recommendations for creating incentive supporting implementation of green roofs in urban areas.

The effect of drainage height on plant-species composition on a semi-arid green roof system

2021 ◽  
Vol 67 (3-4) ◽  
pp. 149-155
Author(s):  
Har'el Agra ◽  
Hadar Shalom ◽  
Omar Bawab ◽  
Gyongyver J. Kadas ◽  
Leon Blaustein
Keyword(s):  
Species Composition ◽  
Plant Species ◽  
Plant Diversity ◽  
Urban Areas ◽  
Green Roof ◽  
Growing Season ◽  
Green Roofs ◽  
Plant Species Composition ◽  
Roof System ◽  
Semi Arid

Abstract Green roofs are expected to contribute to higher biodiversity in urban surroundings. Typically, green roofs have been designed with low plant diversity. However, plant diversity can be enhanced by controlling resource availability and creating distinct niches. Here we hypothesize that by using different drainage heights during the short plant-growing season in a semi-arid green roof system we can create distinct niches and plant communities. Our experiment took place at the University of Haifa, north Israel. We tested three different heights of drainage outlet: 10 cm under the surface of the substrate (Low), 1 cm under the surface of the substrate (Medium) and 3 cm above the surface of the substrate (High) on plant species-composition in green-roof gardens. Grasses cover was higher in High and Medium drainages while forbs cover was higher in Low drainage. Species richness was the highest in Low drainage while diversity indices showed the opposite trend. We conclude that by changing the height of the drainage we can create different niches and change species composition in a short time period of one growing season. This way we can create more diverse green roof communities and enhance biodiversity in urban areas, particularly in semi-arid regions.

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.

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