The Experts below are selected from a list of 11364 Experts worldwide ranked by ideXlab platform
E W Tollner - One of the best experts on this subject based on the ideXlab platform.
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modeling stormwater runoff from Green Roofs with hydrus 1d
Journal of Hydrology, 2008Co-Authors: Roger N Hilten, Thomas M Lawrence, E W TollnerAbstract:Summary A study was conducted on the effectiveness of Green Roofs to mitigate stormwater using computer simulation. In this study, the stormwater performance was simulated for a modular block Green roof using a packaged soil moisture simulation, HYDRUS-1D, with simulation results verified by study site data. Simulations were run using HYDRUS-1D for 24-h design storms to determine peak flow, retention and detention time for runoff. Storm data collected as part of a Green roof study in Athens, Georgia, USA were used to validate HYDRUS-simulated runoff. The study site consisted of a 37 m2 (400 ft2) modular block Green roof containing engineered soil and vegetation including several Sedum species. The study revealed that rainfall depth per storm strongly influences the performance of Green Roofs for stormwater mitigation, providing complete retention of small storms (
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modeling stormwater runoff from Green Roofs with hydrus 1d
Journal of Hydrology, 2008Co-Authors: Roger N Hilten, Thomas M Lawrence, E W TollnerAbstract:A study was conducted on the effectiveness of Green Roofs to mitigate stormwater using computer simulation. In this study, the stormwater performance was simulated for a modular block Green roof using a packaged soil moisture simulation, HYDRUS-1D, with simulation results verified by study site data. Simulations were run using HYDRUS-1D for 24-h design storms to determine peak flow, retention and detention time for runoff. Storm data collected as part of a Green roof study in Athens, Georgia, USA were used to validate HYDRUS-simulated runoff. The study site consisted of a 37 m2 (400 ft2) modular block Green roof containing engineered soil and vegetation including several Sedum species. The study revealed that rainfall depth per storm strongly influences the performance of Green Roofs for stormwater mitigation, providing complete retention of small storms (<2.54 cm) and detention for larger storms, assuming the measured average moisture content (∼10%) as the antecedent condition.
Rafik Belarbi - One of the best experts on this subject based on the ideXlab platform.
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experimental study of the urban microclimate mitigation potential of Green Roofs and Green walls in street canyons
International Journal of Low-carbon Technologies, 2015Co-Authors: Rabah Djedjig, Emmanuel Bozonnet, Rafik BelarbiAbstract:This paper presents the design and the results of a reduced-scale experimental bench to study the effect of Green Roofs and Green facades on local urban microclimate. An analysis of experimental data was carried out on three street canyons: one reference street, one street between two buildings with Green Roofs and one with a Green wall to the west. The results show a hygrothermal effect of Green envelopes on buildings on urban heat island mitigation. In the detailed analysis of these Green coating techniques, we highlighted that Green facades modify strongly the radiative balance of the street and improve the hygrothermal comfort in urban canyons through reducing the overheating in the street in hot summer days.
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development and validation of a coupled heat and mass transfer model for Green Roofs
International Communications in Heat and Mass Transfer, 2012Co-Authors: Rabah Djedjig, Salaheddine Ouldboukhitine, Rafik Belarbi, Emmanuel BozonnetAbstract:Abstract This paper describes a dynamic model of transient heat and mass transfer across a Green roof component. The thermal behavior of the Green roof layers is modeled and coupled to the water balance in the substrate that is determined accounting for evapotranspiration. The water balance variations over time directly impact the physical properties of the substrate and the evapotranspiration intensity. This thermal and hydric model incorporates wind speed effects within the foliage through a new calculation of the resistance to heat and mass transfer within the leaf canopy. The developed model is validated with experimental data from a one-tenth-scale Green roof located at the University of La Rochelle. A comparison between the numerical and the experimental results demonstrates the accuracy of the model for predicting the substrate temperature and water content variations. The heat and mass transfer mechanisms through Green Roofs are analyzed and explained using the modeled energy balances, and parametric studies of Green roof behavior are presented. A surface temperature difference of up to 25 °C was found among Green Roofs with a dry growing medium or a saturated growing medium. Furthermore, the thermal inertia effects, which are usually simplified or neglected, are taken into account and shown to affect the temperature and flux results. This study highlights the importance of a coupled evapotranspiration process model for the accurate assessment of the passive cooling effect of Green Roofs.
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a comprehensive study of the impact of Green Roofs on building energy performance
Renewable Energy, 2012Co-Authors: Issa Jaffal, Salaheddine Ouldboukhitine, Rafik BelarbiAbstract:Green Roofs have several environmental benefits, such as improving building energy efficiency. The present paper provides a comprehensive study of the impact of a Green roof on building energy performance. A model of Green roof thermal behavior was coupled with a building code to allow the evaluation of Green roof foliage and soil surface temperatures. Simulations were conducted for a single-family house with conventional and Green Roofs in a temperate French climate. In the summer, the fluctuation amplitude of the roof slab temperature was found to be reduced by 30°C due to the Green roof. The heat flux through the roof was also evaluated. In the summer, the roof passive cooling effect was three times more efficient with the Green roof. In the winter, the Green roof reduced roof heat losses during cold days; however, it increased these losses during sunny days. The impact of the Green roof on indoor air temperature and cooling and heating demand was analyzed. With a Green roof, the summer indoor air temperature was decreased by 2°C, and the annual energy demand was reduced by 6%. The present study shows that the thermal impact of Green Roofs is not functionally proportional to the leaf area index parameter. It also shows the high dependency of this impact on the roof insulation. Finally, the simulations suggest that Green Roofs are thermally beneficial for hot, temperate, and cold European climates.
Roger N Hilten - One of the best experts on this subject based on the ideXlab platform.
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modeling stormwater runoff from Green Roofs with hydrus 1d
Journal of Hydrology, 2008Co-Authors: Roger N Hilten, Thomas M Lawrence, E W TollnerAbstract:Summary A study was conducted on the effectiveness of Green Roofs to mitigate stormwater using computer simulation. In this study, the stormwater performance was simulated for a modular block Green roof using a packaged soil moisture simulation, HYDRUS-1D, with simulation results verified by study site data. Simulations were run using HYDRUS-1D for 24-h design storms to determine peak flow, retention and detention time for runoff. Storm data collected as part of a Green roof study in Athens, Georgia, USA were used to validate HYDRUS-simulated runoff. The study site consisted of a 37 m2 (400 ft2) modular block Green roof containing engineered soil and vegetation including several Sedum species. The study revealed that rainfall depth per storm strongly influences the performance of Green Roofs for stormwater mitigation, providing complete retention of small storms (
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modeling stormwater runoff from Green Roofs with hydrus 1d
Journal of Hydrology, 2008Co-Authors: Roger N Hilten, Thomas M Lawrence, E W TollnerAbstract:A study was conducted on the effectiveness of Green Roofs to mitigate stormwater using computer simulation. In this study, the stormwater performance was simulated for a modular block Green roof using a packaged soil moisture simulation, HYDRUS-1D, with simulation results verified by study site data. Simulations were run using HYDRUS-1D for 24-h design storms to determine peak flow, retention and detention time for runoff. Storm data collected as part of a Green roof study in Athens, Georgia, USA were used to validate HYDRUS-simulated runoff. The study site consisted of a 37 m2 (400 ft2) modular block Green roof containing engineered soil and vegetation including several Sedum species. The study revealed that rainfall depth per storm strongly influences the performance of Green Roofs for stormwater mitigation, providing complete retention of small storms (<2.54 cm) and detention for larger storms, assuming the measured average moisture content (∼10%) as the antecedent condition.
Qi Feng - One of the best experts on this subject based on the ideXlab platform.
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quantifying the contributions of structural factors on runoff water quality from Green Roofs and optimizing assembled combinations using taguchi method
Journal of Hydrology, 2021Co-Authors: Wen Liu, Weiping Chen, Wei Wei, Bernard A Engel, Yu Wang, Qi FengAbstract:Abstract Runoff water quality of Green Roofs often comes under debate, and the mechanism of runoff pollution retention is still unclear. How to quantify the influencing contributions of structural factors to runoff pollution of Green Roofs and optimize the assembled combinations for improving water quality are ambiguous. In this study, runoff plots of extensive Green Roofs with Taguchi designed structural factors and levels were constructed and simulated rainfall experiments were conducted. Influences of structural factors on outflow water quality of Green Roofs were statistically assessed and quantified. Runoff water quality of Green Roofs with assembled combinations at specific levels were optimized and predicted by using the Taguchi method. Results showed that except for the pH and NO- 3 concentrations, the extensive Green Roofs acted as a source of the tested pollutants in stormwater runoff. Contributions of substrate materials on pH, EC, ESP (exchangeable sodium percentage), F-, NO- 3 and NO2-N concentrations were the highest among the structural factors, and contribution percentages ranged from 33.38% to 64.47%. The vegetation types had important contributions on Cl-, SO2- 4 and TP concentrations, and the contribution percentage was 74.72%, 71.23% and 45.16% respectively. Influences of substrate depths and slope gradients on outflow water quality were small. Most of the determination coefficients (R2) of regression analysis between the measured and predicted water quality parameters under Taguchi design were ranged from 0.843 to 0.997. Except the pH and NO- 3 parameters, the Taguchi predicted water quality under the optimum conditions were improved by 10.2-77.6%. These results will aid understanding of the retention mechanism of Green Roofs on runoff pollutants and improving runoff water quality through the optimization of Green roof design.
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the impacts of substrate and vegetation on stormwater runoff quality from extensive Green Roofs
Journal of Hydrology, 2019Co-Authors: Wen Liu, Weiping Chen, Wei Wei, Ravinesh C Deo, Qi FengAbstract:Abstract Green Roofs are emerging as practical strategies to retain stormwater runoff and improve water environment quality of urban cities. However, the impacts of Green Roofs on stormwater runoff quality remains a topic of concern to urban planners and mangers. In this study, we designed the scale based runoff plots of extensive Green Roofs with different substrate and vegetation types, and investigate whether the studied Green Roofs act as a sink or source of nutrients and suspended solids in their runoff compared to a conventional roof. The influences of substrate and vegetation on the water quality of Green roof outflows were also assessed. The results showed that the average TSS (total suspended solids), TN (total nitrogen), and TP (total phosphorus) concentrations of the Green roof runoff were all significantly higher than that of the conventional roof runoff. Except substrate S3 (the composition ratio of rural soil:peat soil:perlite:vermiculite was 2.5:5:2:0.5) and S1 (the composition ratio of rural soil: peat soil was 1:1) in TP, the substrate S2 (the composition ratio of rural soil:peat soil:pine needle:perlite was 1:1:1:1) displayed significantly higher TN and TP concentrations than either of the runoff from the substrate S1 and S3. The TN and TP concentrations of 5 cm substrate depth were significantly lower than that in the 15 cm substrate depth treatments. Significant differences were observed in TN concentrations between vegetation Sedum Spectabile and Radix Ophiopogonis. However, no significant differences were observed between any of the vegetation types with regard to TP concentrations. Therefore, we suggest that Green Roofs need to be constructed of suitable substrate materials and plants based on their function on runoff water quality in order to mitigate the pollution risk of Green roof runoff on urban water environment.
Martin Hermy - One of the best experts on this subject based on the ideXlab platform.
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do looks matter a case study on extensive Green Roofs using discrete choice experiments
Sustainability, 2018Co-Authors: Jan Vanstockem, Liesbet Vranken, Brent Bleys, Ben Somers, Martin HermyAbstract:Extensive Green Roofs are a promising type of urban Green that can play an important role in climate proofing and ultimately in the sustainability of our cities. Despite their increasingly widespread application and the growing scientific interest in extensive Green Roofs, their aesthetics have received limited scientific attention. Furthermore, several functional issues occur, as weedy species can colonize the roof, and extreme roof conditions can lead to gaps in the vegetation. Apart from altering the function of a Green roof, we also expect these issues to influence the perception of extensive Green Roofs, possibly affecting their acceptance and application. We therefore assessed the preferences of a self-selected convenience sample of 155 Flemish respondents for visual aspects using a discrete choice experiment. This approach, combined with current knowledge on the psychological aspects of Green roof visuals, allowed us to quantify extensive Green roof preferences. Our results indicate that vegetation gaps and weedy species, together with a diverse vegetation have a considerable impact on Green roof perception. Gaps were the single most important attribute, indicated by a relative importance of ca. 53%, with cost coming in at a close second at ca. 46%. Overall, this study explores the applicability of a stated preference technique to assess an often overlooked aspect of extensive Green Roofs. It thereby provides a foundation for further research aimed at generating practical recommendations for Green roof construction and maintenance.
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runoff and vegetation stress of Green Roofs under different climate change scenarios
Landscape and Urban Planning, 2014Co-Authors: Eline Vanuytrecht, Carmen Van Mechelen, Koenraad Van Meerbeek, Patrick Willems, Martin Hermy, Dirk RaesAbstract:Abstract Green Roofs are efficient tools to improve life quality in densely populated areas. The contribution to the reduction of stormwater runoff and the heat-island effect may even augment with climate change. In this study, impacts of climatic changes on vegetation drought stress and stormwater retention of two Green roof types (one with sedum-moss vegetation, one with grass-herbs vegetation) and a standard bitumen roof were assessed using a water balance model (GreenRoof). A case study of the Flemish region in Belgium was done, but the study can be representative for temperate maritime climates worldwide. Local weather data for the 2050s were generated with the LARS-WG weather generator based on climate scenarios from two multi-model ensembles of respectively 15 global and 9 regional climate models. Under the projected differences in precipitation and evaporating power of the atmosphere, runoff was expected to decrease in summer and to increase in winter on all roof types. Grass-herb Green Roofs could reduce runoff more than sedum-moss Green Roofs, but were more sensitive to increased drought stress. Both Green roof types were shown to remain a valid option for runoff reduction in urban areas as compared to bitumen Roofs, mainly in summer. The benefit of Green Roofs can increase under climatic changes but increased vegetation stress urges reconsideration of Green roof design and vegetation choice to obtain an optimal runoff reduction and vegetation survival.
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Green Roofs as a tool for solving the rainwater runoff problem in the urbanized 21st century
Landscape and Urban Planning, 2006Co-Authors: Jeroen Mentens, Dirk Raes, Martin HermyAbstract:During the last two decades, a large amount of research has been published in German on the reduction of rainwater runoff for different types of roof Greening. This paper analyzes the original measurements reported in 18 publications. Rainfall–runoff relationships for an annual and seasonal time scale were obtained from the analysis of the available 628 data records. The derived empirical models allowed us to assess the surface runoff from various types of Roofs, when roof characteristics and the annual or seasonal precipitation are given. The annual rainfall–runoff relationship for Green Roofs is strongly determined by the depth of the substrate layer. The retention of rainwater on Green Roofs is lower in winter than in summer. The application of the derived annual relationship for the region of Brussels showed that extensive roof Greening on just 10% of the buildings would already results in a runoff reduction of 2.7% for the region and of 54% for the individual buildings. Green Roofs can therefore be a useful tool for reducing urban rainfall runoff. Yet in order to provide a greater effect on overall runoff they should be accompanied by other means of runoff reduction and/or water retention. © 2005 Elsevier B.V. All rights reserved.
