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Green roof systems (GRs) are effective tools for urban stormwater management. However, there is limited documentation of the long-term hydrological performance of GRs to support decision-making. This study evaluated long-term field monitoring records (7 years) from a 12-year-old GR, situated in a Moist Subtropical Mid-Latitude Climate, to analyze seasonality in and evolution of hydrological performance. The monitoring system was built within a pan lysimeter buried under substrate layers matching the surrounding GR. The monitoring results highlight the efficacy of this GR in long-term stormwater runoff control. The GR can retain 87% of the annual precipitation and return 54% of the precipitation to the atmosphere through evapotranspiration (ET) and sustain long-term event-based mean runoff volume reductions, peak flow reductions, and flow delays of 82%, 93%, and 4.3 h, respectively. The initial moisture content prior to events was highly correlated with hydrological performance, with a seasonal mean Spearman correlation coefficient of 0.47, suggesting the potential of enhancing ET from the GR to improve performance. Substrate water holding capacity increased over time, but no obvious changes in water retention performance were observed. These monitoring results from the aging GR demonstrate the effectiveness of GR systems for long-term stormwater management. [Display omitted] • A GR was monitored using a sensor network for >10 years. • The GR presented a long-term mean event retention of 82%. • The GR retention was more sensitive to initial moisture content than precipitation. • Evolution of soil water properties did not obviously decrease water retention. [ABSTRACT FROM AUTHOR]

Water scarcity has generated the need to identify new sources. Due to its low organic contaminant load, greywater reuse has emerged as a potential alternative. Moreover, the search for decentralized treatment systems in urban areas has prompted research on using green roofs for greywater treatment. However, the performance of organic matter removal is limited by the type of substrate and height of the growing media. Bioelectrochemical systems (BESs) improve treatment performance by providing an additional electron acceptor (the electrode). In this study, nine reactors under three different conditions, i.e., open circuit (OC), microbial fuel cell (MFC), and microbial electrolysis cell (MEC), were built to evaluate the treatment of synthetic greywater in a substrate-growing medium composed of perlite and coconut fiber and operated in batch-cycle mode for 397 days. The results suggested that using BESs enables greywater treatment and the removal of pollutants to levels that allow their reuse for irrigation. Furthermore, electrical conductivity was reduced from 732.4 ± 41.2 μS/cm2 in OC to 637.32 ± 22.73 μS/cm2 and 543.15 ± 19.69 μS/cm2 in MEC and MFC, respectively. The soluble chemical oxygen demand in the latter treatments reached 76% removal, compared to levels above the OC, which only reached approximately 67%. Microbial community analysis revealed differences, mainly in the cathodes, showing a higher development of Flavobacterium , Azospirillum , and Zoogloea in MFCs, which could explain the higher levels of organic matter removal in the other conditions, suggesting that the BES could produce an enrichment of beneficial bacterial groups for treatment. Therefore, implementing BESs in green roofs enables sustainable long-term greywater treatment. [Display omitted] • The substrate depth is a relevant factor in greywater treatment on green roofs. • Bioelectrochemical systems in a low-height substrate enhance greywater treatment. • Long-term organic matter removal was improved and 90% of surfactants was removed. • Electrical conductivity was reduced in bioelectrochemical systems. • Bioelectrochemical systems enriched organic matter degrading bacterial groups. [ABSTRACT FROM AUTHOR]

Green roof systems have been developed to improve the environmental, economic, and social aspects of sustainability. Selecting the appropriate version of the green roof composition plays an important role in the life cycle assessment of a green roof. In this study, 10 compositions of an intensive green roof for moderate zone and 4 green roof compositions for different climatic conditions were designed and comprehensively assessed in terms of their environmental and economic impacts within the "Cradle-to-Cradle" system boundary. The assessment was carried out over a 50-year period for a moderate climate zone. The results showed that asphalt strips and concrete slab produced the highest total emissions. It was found that most greenhouse gases emissions were released in the operational energy consumption phase and in the production phase. The energy consumption phase (48.78%) for automatic irrigation and maintenance caused the highest Global Warming Potential (GWP) value (758.39 kg CO 2e) in the worst variant, which also caused the highest life cycle cost (878.47€). On the contrary, in the best variant, planting more vegetation and lower maintenance and irrigation requirements led to a reduction in GWP (445.0 kg CO 2e), but in terms of cost (506.6€) this composition didn't represent the best variant. The Global Warming Potential Biogenic (GWP-bio) compared to the Global Warming Potential Total (GWP-total) represents a proportion ranging from 0.8% to 78% depending on the proposed vegetation. Overall higher biogenic carbon values (up to 1525 kg CO 2e) were observed for the proposed tall vegetation of Magnolia, Red Mulberry, Hawthorne, Cherry, and Crab-apple Tree. Based on the results of the multicriteria analysis, which included core environmental & economic parameters, biogenic carbon emission levels, the outcome of this paper proposed optimal green roof composition. Optimal intensive green roof composition was subjected to a sensitivity analysis to determine the impact of changing climatic conditions on CO 2 emissions and life cycle costs. The results of the sensitivity analysis show that the optimal variant of the green roof can be implemented in the cold and subtropical zone with regard to CO 2 emissions, but not with regard to life cycle costs. • Ten compositions of intensive green roofs were designed and evaluated in terms of environmental and economic aspects. • Energy consumption for automatic irrigation and maintenance caused the highest GWP (48.78%) andlife cycle cost (69.55%). • The application of high green vegetation has a significant effect on CO 2 sequestration and contributes to GWP bio. • Through multicriteria analysis identified the design of the optimal green roof composition. • The most optimal composition was adapted for conditions in different climate zone. [ABSTRACT FROM AUTHOR]

Lack of studies in developing countries with tropical climate such as the Philippines limit local LID adoption. This study compared the performance of different LID scenarios across different urban land use types at the sub-catchment level using peak flow, runoff volume and flood reductions as performance criteria. Results showed that the most effective strategies for each land use are: 1) combined green roof and bioretention for low-density residential (reduction up to 10% peak flow, 11% runoff volume and 33% flood volume); 2) green roof for high-density residential (8% peak flow, 6% runoff volume and 18% flood volume); 3) combined rain barrel, bioretention and permeable pavement for industrial (23% peak flow, 41% runoff volume and 56% flood volume), and 4) combined vegetative swale and detention pond for urban open spaces (81% peak flow, 8% runoff volume and 84% flood volume). While effective for most low intensity storms, the observed sharp decrease in LID performance with increased rainfall intensity poses a major challenge, especially in the context of the Philippines frequented by high intensity storms. This study also examined how differences in land use characteristics influence LID performance, unlike most studies that focused on LID type comparisons. It showed that low urban density setting positively affected peak flow and flood reduction performance of rain barrels and green roofs, while good drainage infrastructure quality positively affected peak flow and flood reduction performance of rain barrels and bioretention. Decision-makers may use these findings to conduct rapid assessments on LID selection and siting, provided similarities between land use characteristics described in this study and those at their localities are justified. This can lead to increased LID adoption towards building water resilient, and sustainable cities. [Display omitted] • Realistic LID types suited for different urban land uses in a developing country setting are limited. • LID performances in a tropical setting are generally lower than areas with different climates. • Choosing the best LID depends on site's land use characteristics and chosen performance criteria. • Low urban density setting positively affected performance of rain barrels and green roofs. • Good drainage setting positively affected performance of rain barrels and bioretention. [ABSTRACT FROM AUTHOR]

Dhaka ranks among the world's most densely populated cities, with built-up areas expanding to accommodate the demands of a growing population. The rapid urbanization has reduced green space and exacerbated urban heat and pollution in the city. In the quest for a greener and healthier urban environment, rooftop agriculture has emerged as a promising solution, offering opportunities for the restoration of the environment and safe food production. Despite its potential, limited studies have explored the viability of this alternative greening solution for Dhaka. Therefore, this study aims to assess the suitability of rooftops for agricultural activities employing Geographic Information System (GIS) and Multi-Criteria Decision Making (MCDM) techniques. First, seven criteria were selected based on the literature, such as building age, height, rooftop size, building utility, property value, sunlight, and water availability. Second, an expert opinion survey was conducted using the Best Worst Method (BWM) to calculate the criteria's weights. Finally, the suitability map for Dhaka was derived by combining the criteria layers and was subsequently validated. Rooftop area and property value were identified as the most and least important criteria. Approximately 9% (6.27 km2), 68% (46.59 km2), 22% (15.15 km2), and a negligible portion (0.1 km2) of Dhaka city has been classified as highly suitable, suitable, moderately suitable, and not suitable, respectively, for rooftop agriculture. By identifying and promoting the most suitable locations for rooftop agriculture and highlighting existing opportunities, this research will help to initiate and expand sustainable agriculture practices that can contribute to climate change adaptation and urban resilience. [Display omitted] • This study examines the feasibility of one urban greening solution in Dhaka. • The study employs GIS and MCDM techniques to assess rooftop suitability. • The analysis reveals that rooftop area is a key factor for rooftop agriculture. • About 77% of the total rooftop area is suitable or highly suitable for this purpose. • The study provides insights to promote vertical greening initiatives in dense cities. [ABSTRACT FROM AUTHOR]

In the face of escalating urban pluvial floods exacerbated by climate change, conventional roof systems fall short of effectively managing precipitation extremes. This paper introduces a smart predictive solution: the Smart Internal Drainage Roof (SIDR) system, which leverages forecasted data to enhance the mitigation of pluvial floods in Central Business District (CBD) areas. Unlike traditional approaches, SIDRs utilize a synergistic combination of Rule-based Control (RBC) and Model Predictive Control (MPC) algorithms, tailored to optimize the operational efficiency of both grey and green roofs. Within the examined 1.3 km2 area in Beijing, China, SIDRs, covering 11% of the site, decreased total flooded areas by 30%–50% and eliminated 60%–100% of high-risk zones during three actual events. Moreover, SIDRs streamlined outflow processes without extending discharge time and reduced flood duration at a high-risk underpass by more than half. The SIDR's distinct features, including a high control resolution of 5 min, integration with existing waterproofs, and advanced 2D dynamic runoff visualization, position it as a scalable and cost-efficient upgrade in urban flood resilience strategies. [Display omitted] • SIDRs employ RBC and MPC algorithms to mitigate pluvial floods in CBDs. • SIDRs reduce 30%–50% of flooded areas and 60%–100% of high-risk zones. • Runoff control dynamics of SIDRs are illustrated on high-precision 2D girds. • SIDRs can streamline outflow processes without prolonging discharge time. [ABSTRACT FROM AUTHOR]

Urban flooding poses a significant challenge to the rapidly growing Indian cities. Low-impact development strategies such as green roofs have shown the potential to reduce urban flooding. However, their performance assessment significantly varies across different studies. Therefore, the study's primary objective is to evaluate green roofs in the Indian context. For this evaluation, the green roofs are assessed based on building-level implementation scenarios for a high-density urban area in India for 25%,50%, and 75% application rates and different rainfall intensities (2,3 and 4-h duration and 2,5,10 and 25-year frequencies). Secondly, to probe the variations in the green roof performance across studies, uncertainty contributions to the runoff reduction from different parameters are quantified. The results show that green roofs can reduce up to 62% of flood volume and 24% of runoff. However, they are reasonably effective only beyond 25% application rates. Further, rainfall intensity contributes the most to the uncertainty of runoff reduction from green roofs. This uncertainty assessment implies that localized evaluation of green roofs depending on local rainfall conditions is required for city-wide policy planning. The study has a significant contribution to building confidence in the ability of green roofs to reduce urban floods in the context of developing countries like India. • Green roof performance is assessed through building-level implementation scenarios. • Green roofs show a reduction of up to 62% in flood volume and 24% in runoff. • Green roofs are reasonably effective only at a minimum 25% application rate. • Rainfall intensity contributes the highest to the total performance uncertainties. • Uncertainty quantification can explain performance variations across studies. [ABSTRACT FROM AUTHOR]

By infiltrating and retaining stormwater, Blue-Green Infrastructure (BGI) can help to reduce Combined Sewer Overflows (CSOs), one of the main causes of urban water pollution. Several studies have evaluated the ability of individual BGI types to reduce CSOs; however, the effect of combining these elements, likely to occur in reality, has not yet been thoroughly evaluated. Moreover, the CSO volume reduction potential of relevant components of the urban drainage system, such as detention ponds, has not been quantified using hydrological models. This study presents a systematic way to assess the potential of BGI combinations to mitigate CSO discharge in a catchment near Zurich (Switzerland). Sixty BGI combinations, including four BGI elements (bioretention cells, permeable pavement, green roofs, and detention ponds) and four different implementation rates (25%, 50%, 75%, and 100% of the available sewer catchment area) are evaluated for four runoff routing schemes. Results reveal that BGI combinations can provide substantial CSO volume reductions; however, combinations including detention ponds can potentially increase CSO frequency, due to runoff prolongation. When runoff from upstream areas is routed to the BGI, the CSO discharge reductions from combinations of BGI elements differ from the cumulative CSO discharge reductions achieved by individual BGI types, indicating that the sum of effects from individual BGI types cannot accurately predict CSO discharge in combined BGI scenarios. Moreover, larger BGI implementation areas are not consistently more cost-effective than small implementation areas, since the additional CSO volume reduction does not outweigh the additional costs. The best-performing BGI combination depends on the desired objective, being CSO volume reduction, CSO frequency reduction or cost-effectiveness. This study emphasizes the importance of BGI combinations and detention ponds in CSO mitigation plans, highlighting their critical factors—BGI types, implementation area, and runoff routing— and offering a novel and systematic approach to develop tailored BGI strategies for urban catchments facing CSO challenges. [Display omitted] • CSO reductions of combined BGI are different from the sum of individual BGI. • Runoff routing scheme substantially affects the performance of BGI combinations. • Detention ponds reduce CSO volume yet prolong CSO discharge. • Large implementation areas are less cost-effective than small ones. • The selection of the best-performing BGI combinations has trade-offs. [ABSTRACT FROM AUTHOR]

Green roofs are well studied for the environmental, social, and economic services these provide. As a result, green roofs are widespread and within the common vernacular of city residents. Green roof bylaws and construction standards are present in many cities in North America, rooting the presence of this green infrastructure within urban landscapes. Although examples of green roofs constructed decades ago exist, rarely are green roofs monitored over such long periods, and in ways that allow for experimentation, analysis, and conclusions about performance or function. In this study we present findings on plant cover and biomass from a green roof testing facility in Toronto, Canada that was monitored for over a decade. We examine the contributions of growing media, planting, and irrigation in the first seven years (2011–2021) of the eleven-year monitoring period. We found that during this maintenance phase period (2011–2017), plant cover and biomass was highest in modules planted with Sedum , included organic media, and were irrigated, whereas non-irrigated modules planted with forbs and grasses had the poorest performance regardless of media type. Following the stoppage of irrigation, and the post maintenance phase (2017–2021), modules initially planted with Sedum continued to sustain cover and biomass whereas planted forbs and grasses mostly disappeared, and these treatments were overtaken by Sedum. Our findings demonstrate that with irrigation, plantings of forbs and grasses can sustain plant cover and biomass. However, Sedum buffers against major changes to environmental conditions or abrupt changes to maintenance, adding insurance against failure of extensive green roofs. • Combos of plants, media, and irrigation were studied on green roofs for 10 years. • Sedum maintained plant cover and biomass more consistently than forbs and grasses. • With irrigation and organic media, forbs and grasses sustain cover and biomass. • Sedum buffers against disruptions to maintenance and adds insurance against failure. • We list 10 lessons learned from long-term research co-produced with practitioners. [ABSTRACT FROM AUTHOR]

This paper uses an expert-based methodology to survey the barriers and strategies related to the implementation of nature-based solutions (NBS). The ambition of the paper is to offer a bird's eye overview of the difficulties encountered by NBS deployment and ways to overcome them. With a wide participation of 80 experts from COST Action Circular City, we identify barriers specific to 35 pre-defined NBS of the following four categories: Vertical Greening Systems and Green Roofs; Food and Biomass Production; Rainwater Management; and Remediation, Treatment, and Recovery. The research sheds light on how a major interdisciplinary – yet predominantly technically-oriented - community of scientists and practitioners views this important topic. Overall, the most relevant barriers are related to technological complexity, lack of skilled staff and training programs and the lack of awareness that NBS is an option. Our results highlight concerns related to post implementation issues, especially operation and maintenance, which subsequently affect social acceptance. The paper identifies a "chain" effect across barriers, meaning that one barrier can affect the existence or the relevance of other barriers. In terms of strategies, most of them target governance, information, and education aspects, despite the predominantly technical expertise of the participants. The study innovates with respect to state-of-the-art research by showing a fine-grained connection between barriers, strategies and individual NBS and categories, a level of detail which is not encountered in any other study to date. [Display omitted] • Mixed qualitative-quantitative expert-based approach to discern barriers and strategies for implementing NBS. • Extend expert panel globally, analyze trade-offs, consider local context, address sociopolitical complexities. • Transversal barriers include technological complexity, lack of skilled staff, lack of awareness of NBS as a valid option. • Identified key strategies to overcome barriers call for improvement of information, education and governance. [ABSTRACT FROM AUTHOR]

China has begun a rapid move towards Sponge City implementation, which will include widespread installation of various Low Impact Development (LID) stormwater infrastructure. Ambitious goals have been set for all Sponge Cities, including a target capture rate of 80–85% of annual precipitation in Beijing. However, there has so far been limited investigation into whether these goals are obtainable at the catchment scale given the physical restrictions of the existing urban landscape. This paper demonstrates the use of long-term continuous hydrologic modelling to evaluate the potential of meeting rainfall capture goals over a long time period for a case study area in Beijing. Detailed land cover classification derived from satellite imagery aided in the parameterization of a SWMM (Stormwater Management Model) model representing a 133 km2 urban study area. The calibrated and validated model demonstrated satisfactory agreement between computed and observed runoff for a variety of precipitation events ranging from 10 to 207 mm. A synthetic high resolution rainfall time series was generated from historic daily observations then used as input to run the model continuously for a 35 year period. Feasible LID model scenarios based on varying degrees of implementation of rain gardens, permeable pavements and green roofs were compared in terms of their potential volume capture of annual rainfall. Modelling results demonstrated that the conversion of 30% of roof area to green roof, 10% of green areas to rain gardens and 35% of paved areas to permeable pavement could increase the baseline volume capture ratio from 59.9% to 82.2%, indicating that Sponge City goals can be met within the case study area with realistic levels of LID implementation. This study provides a decision-making basis for future planning in the study area. • Satellite imagery based hydrologic model shows good agreement with observed flows. • Continuous modelling approach suggested for evaluation of Volume Capture Ratio. • >80% of annual rainfall captured with moderate catchment wide implementation of LID. [ABSTRACT FROM AUTHOR]

This paper presents a methodology for assessing the selection of stormwater control measures (SCM) within an urban drainage system that combines hydrological-hydraulic modelling and multi-criteria analysis (MCA). The methodology's utility is illustrated on urban catchment in the city of Girona, Spain. The SWMM model was applied and calibrated to simulate SCM scenarios. Seven scenarios were evaluated consisting of one grey infrastructure measure using underground storage tank and three nature-based SCM i.e. infiltration basins, infiltration trenches, green roofs, and combinations thereof. These scenarios were evaluated with MCA including combined sewer overflow (CSO) reduction, CAPEX, OPEX, amenity, biodiversity, and feasibility regarding ownership. The results show that the scenario that included only infiltration basins was most favourable, followed by the scenario which combined infiltration basins and trenches. The underground storage tank was the least favourable with the lowest grade, due to high CAPEX and OPEX, and due to single functionality. Image 1 • Methodology for multi-criteria assessment of stormwater control measures. • Nature-based and conventional measures evaluated in real urban catchment. • Scenarios of measures implementation evaluated using MCA. • Infiltration basins proved to be the most favourable measure for given conditions. [ABSTRACT FROM AUTHOR]

Abstract Green roofs can significantly reduce stormwater runoff volumes. Plant selection is crucial to retention performance, as it is influenced by how well plants dry out substrates between rainfall events. While the role of plants in evapotranspiration (ET) on green roofs is well-studied, their potential influence on retention via their impacts on water movement through substrates is poorly understood. We used a simulated rainfall experiment with plant species with different water use strategies to determine the key drivers of green roof retention performance. Overall per-event retention was very high (89–95%) and similar for all plant species and unplanted modules for small events. However, for larger events, some species showed lower retention than unplanted modules or low-water using succulent species. Despite the fact that these species were more effective at replenishing storage between rainfall events due to their higher ET , they reduced the maximum storage capacity of the substrate, likely due to their root systems creating preferential flow paths. This finding has important implications for green roofs, as although ET represents the primary means by which the storage capacity of green roofs can be regenerated, if species with high ET also reduce the maximum storage capacity, effective retention performance is reduced. Therefore, we suggest that species selection must first focus on how plants affect storage capacity in the first instance and consider water use strategies as a secondary objective. Highlights • We evaluated plant effects on rainfall retention. • Rainfall retention depends more on substrate storage capacity than on ET. • Some species reduce substrate storage through preferential flow paths. • These root-induced preferential flow paths can overwhelm plant ET benefits. [ABSTRACT FROM AUTHOR]

Managing and reducing combined sewer overflow (CSO) discharges is crucial for enhancing the resilience of combined sewer systems (CSS). However, the absence of a standardised resilience analysis approach poses challenges in developing effective discharge reduction strategies. To address this, our study presents a top-down method that expands the existing Global Resilience Analysis to quantify resilience performance in CSS. This approach establishes a link between threats (e.g., rainfall) and impacts (e.g., CSOs) through continuous and long-term simulation, accommodating various rainfall patterns, including extreme events. We assess CSO discharge impacts from a resilience perspective by introducing eight new metrics. We conducted a case study in Fehraltorf, Switzerland, analysing the performance of three green infrastructure (GI) types (bioretention cells, green roofs, and permeable pavements) over 38 years. The results demonstrated that GI enhanced all resilience indices, with variations observed in individual CSO performance metrics and their system locations. Notably, in Fehraltorf, green roofs emerged as the most effective GI type for improving resilience, while the downstream outfall displayed the highest resilience enhancement. Overall, our proposed method enables a shift from event-based to continuous simulation analysis, providing a standardised approach for resilience assessment. This approach informs the development of strategies for CSO discharge reduction and the enhancement of CSS resilience. [Display omitted] • Proposes a method to quantify resilience by linking system threats to impacts. • New rainfall and CSO metrics provide insight into resilience impact. • Long-term analysis shifts from an event-based to an enhanced resilience assessment. • Spatial analysis reveals diverse resilience patterns in outfall behaviour. • Green infrastructure enhances resilience, but its contribution varies. [ABSTRACT FROM AUTHOR]

Green roofs have been extensively investigated in recent years, showing that their implementation in urban areas provides multiple benefits (e.g., pluvial flood mitigation, urban heat island reduction, energy saving, increase of biodiversity, CO 2 sequestration) and supports sustainable urban development. Although green roof benefits have been widely recognized, the perception that the community has of these nature-based solutions and the willingness to pay for their installation in urban areas is still not clear nor quantified. Societal perception and willingness to pay for green roofs are fundamental for urban planners and decision makers, since they represent the community participation in the sustainable development of urban areas. In this work, we aim to analyze how citizens perceive green roofs and how willing they are to pay for the installation and maintenance of these nature-based solutions. We used an online survey to investigate the perception and the knowledge of green roofs as a potential solution to common environmental issues (i.e., urban flood, increase of temperature, energy consumption, air pollution and lack of green spaces), and the interest and willingness to pay for green roof installation on both public and private roofs. Based on the answers of 389 respondents living in Sardinia (Italy), our analysis revealed that most citizens are aware of what green roofs are, and they are aware that, although these nature-based solutions can not completely solve environmental issues, they can greatly contribute to the mitigation of these phenomena. Results also show a higher interest in the installation of green roofs on public buildings than on private ones, due to the high installation costs. Moreover, for private roofs, the possibility to install photovoltaic panels instead of GRs is generally preferred. Most of the respondents are willing to spend less than 100 € per year for the maintenance of green roofs on public buildings and to invest less than 5000 € for the installation on their own house. • Choice experiment to assess citizens' willingness to pay for green roofs. • High community interest in having green roofs on public buildings. • On private buildings photovoltaic panels are preferred to green roofs. [ABSTRACT FROM AUTHOR]

Abstract The combination of green roofs with photovoltaic (PV) panels has been proposed to provide synergistic benefits as the panel is cooled by the presence of the vegetation, and thus produces more electricity, while the solar panel enhances growing conditions for vegetation, and increases abiotic heterogeneity, resulting in higher plant diversity. We tested these hypotheses in a non-irrigated green roof in a Mediterranean climate with replicated plots including green roofs only, green roofs with a PV panel, and a conventional roof surface with a PV panel. We found that presence of a panel resulted in higher heterogeneity in substrate moisture, but there was no effect on plant diversity. Plant species showed enhanced growth in plots with PV, including greater growth of Sedum sediforme and longer flowering time of annual species. On the other hand, arthropod diversity was lower during part of the year, and abundance of some arthropod taxa was lower in green roof plots with PV. The presence of the green roof also did not improve electricity production by the panels. We conclude that in a Mediterranean climate, it would be appropriate to examine the use of irrigation in green roofs with PV panels, including effects on the plant community and on electricity production. Highlights • Presence of a panel resulted in higher heterogeneity in substrate moisture. • There was no effect of photovoltaic panel presence on plant diversity. • Flowering time of annuals and growth of sedum were enhanced in plots with a panel. • Abundance of some arthropod taxa was lower in plots with a photovoltaic panel. • The presence of the green roof did not improve electricity production by the panels. [ABSTRACT FROM AUTHOR]

Rapid urban growth in Mediterranean cities has become a serious environmental concern. Due to this expansion, which covers adjacent horizontal ground, a critical deficit of green areas has been increasing. Moreover, irrigation is considered an important issue since water is one of the most limiting natural resources all over the world. The main objective of this study was to perform a long-term experiment to assess five Mediterranean species for extensive green roof implementation in Mediterranean-climate conditions. Brachypodium phoenicoides , Crithmum maritimum , Limonium virgatum , Sedum sediforme and Sporobolus pungens were grown in experimental modules under well-watered and water-limited conditions (irrigation at 50% and 25% ET 0 , respectively). Plant growth and cover, relative appearance, color evolution and water use were determined periodically for two years. Shoot and root biomass were quantified at the end of the experimental period. The effects of the irrigation treatments and seasonal changes were assessed to identify the advantages and disadvantages of each species according to their environmental performance. All species survived and showed adequate esthetic performance and plant cover during the experiment. S. sediforme registered the lowest variation of relative appearance along the experiment, the highest biomass production and the lowest water consumption. Nevertheless, B. phoenicoides appeared to be an interesting alternative to S. sediforme , showing high esthetic performance and water consumption throughout the rainy season, suggesting a potential role of this species in stormwater regulation related with runoff reduction. S. pungens performed well in summer but presented poor esthetics during winter. [ABSTRACT FROM AUTHOR]

The present study examined whether it is possible to simulate a local herbaceous coastal plant community on a roof, by studying the natural habitats of rocky sea coast plants and their propagation and performance on a green roof. After studying the natural habitat of coastal areas in Izu peninsula, a germination and cutting transplant study was carried out using herbaceous plants from the Jogasaki sea coast. Many plant species did not germinate at all and the use of cuttings was a better method than direct seeding. The green roof was installed in the spring of 2012 in Chiba city. Thirteen plant species from the Jogasaki sea coast, which were successfully propagated, were planted in three kinds of substrate (15 cm depth): pumice, roof tile and commercial green roof substrate. The water drainage was restricted and a reservoir with 5 cm depth of water underlaid the substrate to simulate a similar growing environment to the sea coast. Volcanic rocks were placed as mulch to create a landscape similar to that on the Jogasaki sea coast. Plant coverage on the green roof was measured every month from June 2012 to October 2014. All plants were harvested and their dry shoot weight was measured in December 2014. The type of substrate did not cause significant differences in plant survival and dry shoot weight. Sea coast plant species were divided into four categories: vigorous growth; seasonal change; disappearing after a few years; limited growth. Understanding the ecology of natural habitats was important to simulating a local landscape using native plant communities on the green roof. [ABSTRACT FROM AUTHOR]

In spite of the well-known green roof benefits, their widespread adoption in the management practices of urban drainage systems requires the use of adequate analytical and modelling tools. In the current study, green roof runoff modeling was accomplished by developing, testing, and jointly using a simple conceptual model and a physically based numerical simulation model utilizing HYDRUS-1D software. The use of such an approach combines the advantages of the conceptual model, namely simplicity, low computational requirements, and ability to be easily integrated in decision support tools with the capacity of the physically based simulation model to be easily transferred in conditions and locations other than those used for calibrating and validating it. The proposed approach was evaluated with an experimental dataset that included various green roof covers (either succulent plants - Sedum sediforme , or xerophytic plants - Origanum onites , or bare substrate without any vegetation) and two substrate depths (either 8 cm or 16 cm). Both the physically based and the conceptual models matched very closely the observed hydrographs. In general, the conceptual model performed better than the physically based simulation model but the overall performance of both models was sufficient in most cases as it is revealed by the Nash-Sutcliffe Efficiency index which was generally greater than 0.70. Finally, it was showcased how a physically based and a simple conceptual model can be jointly used to allow the use of the simple conceptual model for a wider set of conditions than the available experimental data and in order to support green roof design. [ABSTRACT FROM AUTHOR]

The harsh and stressful growing environment of extensive green roofs especially in arid environments allows a limited range of plant species to survive. Therefore, achieving plantings to survive in such conditions is a significant challenge. This paper describes an experiment investigating plant selections for extensive green roofs based on chilling (cold season) and drought (warm season) conditions of Iran. Nine species were selected from the three major taxonomic and functional plant groups that are commonly used on extensive green roofs including grasses, groundcovers and sedums. The species namely Agropyron cristatum , Festuca aurundinacea , Festuca ovina , Potentila sp., Frankinia thymifolia , Vinca minor , Sedum acre , Sedum spurinum , Carpobrotus edulis were imposed to natural chilling in autumn and winter using a randomized complete block design. For spring and summer, irrigation regimes at levels (48, 72 and 96 h intervals) in a factorial experiment based on a randomized complete block design with four replications were applied. The results showed that Agropyron cristatum , Frankinia thymifolia and Carpobrotus edulis were the best plants from each class. Carpobrotus edulis was the best choice for cold and warm seasons and this was followed by Frankinia thymifolia and Potentila sp. Vinca minor performed well in the cold seasons and Sedum spurinum appeared to be excellent in the warm seasons. The plants of the experiment showed significantly different appearances in different watering regimes. Little differences in drought tolerances were observed among the forbs and grasses, which must be watered during warm seasons. However, the succulents responded very well to the drought and low watering regimes. Overall, succulents and groundcovers were considered more appropriate for application in warm and cold seasons, respectively. According to the findings, drought and cold weather conditions cannot be a major obstacle for developing extensive green roofs in Iran if considerations are made on selecting its plant species. [ABSTRACT FROM AUTHOR]

Rainwater retention and water content in green roofs are primarily influenced by structural configurations (i.e., soil layer, vegetation layer, and water storage layer) and climatic factors (i.e., rainfall and evapotranspiration (ET)). Based on the principle of water balance, this study proposes a conceptual model for simulating water flow in green roofs with water storage layers. Three green roof model experiments were conducted from August 1st, 2020 to July 31st, 2021 for calibrating and verifying the conceptual model. The proposed model was solved iteratively using a newly developed program in Visual Basic. The results showed that the conceptual model can capture the dynamic variations in the rainwater retention and water content of green roofs well. The average Nash-Sutcliffe efficiency coefficient is 0.65 and the average error is 6%. The annual rainwater retention capacity (RRC) of green roofs in the perennial rainy climate model was on average 28% higher than that in the seasonal rainy climate model. At the expense of water stress, high ET plants significantly increased the annual RRC of green roofs at a low level. As the water storage layer depth increased from zero to 150 mm, the annual RRC of green roofs increased by 41%, and the water stress decreased by 49%. Compared with an increase in water holding capacity and soil depth, the response of the annual RRC and water stress of green roofs for increasing water storage layer depth is much greater. As per climate of Southern China region, the water storage layer depth of 100 mm is found to obtain optimal rainwater retention and irrigation management in green roof with similar soil thickness (100 mm). [Display omitted] • A hydrological conceptual model of green roofs is proposed. • Perennial rainfall increased rainwater retention by 28% versus seasonal rainfall. • Rainwater retention is increased and irrigation is reduced with water storage layers. • The optimal water storage layer depth is suggested as 100 mm. [ABSTRACT FROM AUTHOR]

In the context of increasing urbanization and global warming, there is a growing interest in the implementation of green infrastructure (GI) across different climates and regions. Identifying an appropriate GI design criteria is essential to ensure that the design is tailored to satisfy local environmental requirements. This article aims to compare the hydrological performance of GI facilities in eleven Swedish cities by isolating the effect of climatic conditions using an identical GI design configuration. Long-term simulations based on 23-years of meteorological time-series were used as inputs for the Storm Water Management Model (SWMM) with Low Impact Development (LID) controls representing two types of facilities: a biofilter cell (BC) and a green roof. (GR). Large differences in potential annual and seasonal runoff retention were found between locations, driven mainly by the extent of winter/spring season, and the distribution of precipitation patterns (for BCs) and the sequence of rainy days-dry periods and evapotranspiration rates (for GRs). Winter/spring and summer demonstrated the highest/lowest differences between the seasons, results that suggest that implications for design might be aligned to the spatio-temporal distribution of precipitation patterns, and runoff regimes generated by snowmelt and rain-on-snow events, in locations where snowmelt represent high portion of runoff generation. • Biofilters and green roofs show high inter-annual variations in volume reduction. • Volume reduction is lower in winter and spring than in summer. • Differing climates lead to different green infrastructure (GI) volume reductions. • Spatial variations in volume reductions differ from those of high-intensity rainfall. [ABSTRACT FROM AUTHOR]

Conceptual hydrological models are practical tools for estimating the performance of green roofs. Such models require calibration to obtain parameter values, which limits their use when measured data are not available. One approach that has been thought to be useful is to transfer parameters from a gauged roof calibrated locally (single-site calibration) to a similar ungauged roof in a different location. This study tested this approach by transferring calibrated parameters of a conceptual hydrological model between sixteen extensive green roofs located in four Norwegian cities. The approach was compared with a multi-site calibration scheme that explores trade-offs of model performances between the sites. The results showed that single site calibration could yield optimal parameters for one site and perform poorly in other sites. In contrast, obtaining a common parameter set that yields satisfactory results (Kling Gupta Efficiency >0.5) for different sites, and roof properties could be achieved by multi-site calibration. • This study compared single-site and multi-site calibration of conceptual hydrological models of green roofs. • Single-site calibration yielded optimal parameters for one site that produced poor simulation results in different locations. • Multi-site calibration yielded satisfactory modelling results in different locations and roof properties. [ABSTRACT FROM AUTHOR]

Different low impact development measures have been proposed to make cities more flood-resilient, and recent literature is paying great attention to the evaluation of their direct benefits in terms of flood risk mitigation and the numerous co-benefits that they may offer. This study describes an experimental prototype of a technologically advanced multilayer green roof installed in a Mediterranean urban area (i.e., Palermo, Italy) and explores the results of an analysis of data collected over a one-year monitoring period by a complex sensors network. Multilayer green roofs, or "blue-green" roofs (BGRs), are characterized by a high water retention capacity compared to traditional green roofs due to the presence of an additional storage layer (blue layer), usually equipped with a valve that allows for regulating discharge outflow and water storage. Due to their recent development, BGRs are still scarcely explored in literature and have never been tested before in semi-arid environments, where they could represent valid measures to counter possible climate change and growing urbanization effects. In this study, the hydrological effectiveness of the experimental BGR is quantitatively evaluated by using appropriate indicators, based on the comparison between the hydrological response of the system and an equal size benchmark "grey" roof. The analyses are prevalently focused on the system's stormwater retention function, also investigating the relative contributions of the green layer and the storage layer to the overall retention capacity through the introduction of new BGRs specific indicators. Results emphasize the high impact of storms characteristics, antecedent soil moisture of the green layer, and initial water storage in the blue layer on the system's retention capacity. The overall mean retention rate for the experimental BGR, on average equal to 77% at the daily scale and 61% at the event scale, is comparable to the typical values of traditional extensive green roofs and could be further improved through a "retention-oriented" management of the outflow valve. The system was able to entirely retain almost half of the rainfall events occurred during the monitoring period and, for all the others, it was however extremely effective in reducing runoff peaks and delaying the hydrograph produced. [Display omitted] • Blue-green roofs (BGRs) combine advantages of traditional GRs and RHSs. • Appropriate indices can quantitatively evaluate the hydrological benefits of BGRs. • We analyzed data collected from an experimental system over about one-year period. • On average, runoff is de-peaked (−80%), reduced in volume (−61%) and delayed (4 h). • Rainfall properties and initial conditions strongly impact BGRs retention function. [ABSTRACT FROM AUTHOR]

On-site decentralized urban stormwater management has gained significant momentum in urban planning. Recently, vegetated roofs have been recommended as a viable decentralized stormwater management system and nature-based solution to meet the challenge of urban floods. However, as another type of unconventional green infrastructure, vertical greenery systems (VGS), also known as vegetated facades, have received much less research attention. Even though some researchers suggest that stormwater management by VGS is comparable to that of vegetated roofs, empirical evidence to substantiate this claim is limited. In this study, we conducted rain simulations on newly-built vegetation containers with water storage compartments. These vegetation containers were designed to be incorporated into a VGS specifically for stormwater management. We tested variables that could influence water retention efficiency and evapotranspiration of the containers under field conditions, i.e., inoculation of plant growth-promoting microbes (PGPMs) (Rhizophagus irregularis and Bacillus amyloliquefaciens), different substrate types (sandy loam and reed-based substrate), simulated rain quantity, natural precipitation, substrate moisture, and air temperature. The inoculation of PGPMs significantly reduced runoff quantity from the vegetation containers. Meanwhile, the well-ventilated sandy-loam substrate significantly reduced the remaining water in the water storage compartments over 1-week periods between rain simulation events, achieving high water-use efficiency. The selected microbes were established successfully in the containers and promoted the growth of 2 out of 5 plant species. R. irregularis colonization responded to substrate type and host plant species, while B. amyloliquefaciens population density in the substrate did not respond to these factors. Environmental conditions, such as antecedent substrate moisture, air temperature, and natural precipitation also influenced the efficiency of stormwater retention and/or evapotranspiration. In conclusion, this study provides instructive and practical insights to reduce urban flood risk by using VGS. • Microbial inoculation reduces runoff quantity of a vertical green system. • Water-use efficiency of the system was mainly influenced by substrate type. • Runoff quantity and water-use efficiency were also influenced by weather conditions. • Our prospective vertical greenery system could reduce urban flood risk. [ABSTRACT FROM AUTHOR]

Extensive green roofs are used to increase the surface area covered by vegetation in big cities, thereby reducing the urban heat-island effect, promoting CO 2 sequestration, and increasing biodiversity and urban-wildlife habitats. In Mediterranean semi-arid regions, the deficiency of water necessitates the use in these roofs of overall native plants which are more adapted to drought than other species. However, such endemic plants have been used scarcely in green roofs. For this purpose, we tested two different substrates with two depths (5 and 10 cm), in order to study their suitability with regard to adequate plant development under Mediterranean conditions. A compost-soil-bricks (CSB) (1:1:3; v:v:v) mixture and another made up of compost and bricks (CB) (1:4; v:v) were arranged in two depths (5 and 10 cm), in cultivation tables. Silene vulgaris (Moench) Garcke and Lagurus ovatus L. seeds were sown in each substrate. These experimental units were subjected, on the one hand, to irrigation at 40% of the registered evapotranspiration values (ET 0 ) and, on the other, to drought conditions, during a nine-month trial. Physichochemical and microbiological substrate characteristics were studied, along with the physiological and nutritional status of the plants. We obtained significantly greater plant coverage in CSB at 10 cm, especially for L. ovatus (80–90%), as well as a better physiological status, especially in S. vulgaris (SPAD values of 50–60), under irrigation, whereas neither species could grow in the absence of water. The carbon and nitrogen fixation by the substrate and the aboveground biomass were also higher in CSB at 10 cm, especially under L. ovatus – in which 1.32 kg C m −2 and 209 g N m −2 were fixed throughout the experiment. Besides, the enzymatic and biochemical parameters assayed showed that microbial activity and nutrient cycling, which fulfill a key role for plant development, were higher in CSB. Therefore, irrigation of 40% can maintain an adequate plant cover of both endemic species, particularly in a deeper and soil-containing substrate. [ABSTRACT FROM AUTHOR]

Traditional blue water resources assessment and management may not meet the needs of sustainable water resource utilization; ignoring the number of green water resources will underestimate the availability of water resources. To rationally allocate and scientifically manage the limited water resources, it is necessary to divide the rich and poor flow situation of blue water and green water. The MIKE SHE-MIKE HYDRO integrated coupled model was selected and used in the Yalong River basin to ascertain the blue and green water in the hydrological cycle. The model was calibrated by matching simulated discharge against observed streamflow discharge at the Tongziling Station. At the same time, the research analyzed the component of green water and the total amount of blue water or green water on a temporal scale. The set pair analysis (SPA) was introduced to classify blue water and green water, which can not only understand the amount and distribution characteristics of water resources in the Yalong River Basin but also rationally allocate the total of water resources in the basin from the perspective of the regional water cycle. Furthermore, according to the situation of blue water and green water in the basin, the related policies are formulated to realize the efficient utilization of water resources in the Yalong River basin. • A high-resolution hydrological model of the Yalong river basin is bulit. • The MIKE SHE system as the modeling platform is used to obtain the variation of Bluewater and Greenwater. • The set pair analysis (SPA) was introduced to study the variation of rich and poor Bluewater and Greenwater. • Table Captions. [ABSTRACT FROM AUTHOR]

Green roof stormwater retention performance is fundamentally related to design configurations and climates. Efficient tools for assessing stormwater retention performance of green roofs with various configurations in different climates are highly desirable for practical applications. In this study, a hydrological model which can be used to simulate dynamic changes in moisture content and evapotranspiration of green roofs is developed and tested (with average Nash-Sutcliffe Efficiency of 0.8197 for calibration and 0.8252 for verification) using monitoring data (2018–2019) of four green roofs with various configurations. The model is applied to simulate long-term (1970–2018) moisture content, actual evapotranspiration, and retention performance of green roofs in eight cities across different climates of China. Green roofs built with engineered soil and Portulaca grandiflora show the largest evapotranspiration and thus provide the largest stormwater retention rates (R r), while green roofs with light growing medium and Sedum lineare show the lowest evapotranspiration and R r. R r of green roofs increases as climate changes from humid to arid. Green roofs at Guangzhou (humid climate) provide the lowest R r (28% ± 3%) caused by plenty of rainfall (1827 mm), while green roofs at Urumqi (desert climate) show the lowest mean annual actual evapotranspiration (167–269 mm) but provide the largest R r (84% ± 5%) as a result of the lowest annual rainfall (282 mm). The results highlight that stormwater retention performance of green roofs could be enhanced through configuration optimization. However, a limiting factor in improving green roofs water retention rates may be the peculiarity of local climatic conditions. [Display omitted] • A green roof (GR) hydrological model is developed and tested with observed data. • Long-term stormwater retention rates (R r) of GRs is assessed using the model. • R r Increases as climate changes from humid to arid. • Optimizing configurations can improve R r to the limitations determined by climates. [ABSTRACT FROM AUTHOR]

Biochar, due to its favourable physiochemical properties, has been promoted as an ideal substrate additive on green roofs, with potential benefits to hydrological function. However, biochar is susceptible to water erosion, which may result in biochar loss and water pollution. The use of granulated biochars or biochars in large particle sizes could potentially alleviate biochar erosion loss, but effects on leachate quality have not been investigated. Also, biochar type and particle size influence plant performance, and effects on discharge quality may vary with vegetation. We assessed the effects of unprocessed and granulated biochars at five (0.25–0.5 mm, 0.5–1 mm, 1–2 mm, 2–2.8 mm, 2.8–4 mm) and four (1–2 mm, 2–2.8 mm, 2.8–4 mm, and 4–6.3 mm) particle size ranges, respectively, on leachate quality on a typical green roof substrate, with presence and absence of vegetation (Agastache foeniculum – a drought-tolerant native forb). We evaluated integrated leachate quality using the CCME Water Quality Index (WQI). Unprocessed biochars reduced nutrient leaching due to increased water retention capacity (WRC) and total porosity. In contrast, granulated biochars, although showing less pronounced mitigation of nutrient leaching, reduced total suspended solids (TSS) and improved WQI in leachate due to enhanced plant performance. In addition, small biochar particles better reduced nutrient leaching and particle loss than large biochar particles, possibly due to increased WRC and formation of water-stable aggregates. The presence of vegetation generally reduced the leaching of nutrients and TSS, consistent with plant nutrient uptake and root substrate stabilization. However, plant biomass was correlated with increased total N leaching, likely due to litter inputs and rapid litter decomposition. We conclude that applications of granulated biochars may best improve discharge quality from green roofs through sorption effects and by enhancing plant performance. [Display omitted] • Biochar granulation provides long-term benefits on leachate quality of green roofs. • Unprocessed biochar mitigates nutrient leaching but increases particulate matter loss. • Fine biochar better reduces nutrient loading and particle loss than coarse biochar. • Enhanced vegetation performance improves leachate water quality. • Leachate water quality from granulated biochar treatments is classified as "good". [ABSTRACT FROM AUTHOR]

Green infrastructure (GI) has been gaining increasing attention due to its efficiency in controlling and purifying urban stormwater runoff, creating environmental amenities, and biodiversity conservation. Nevertheless, the existing knowledge of people's preferences for GI is not yet sufficient for evidence-based policymaking for enhancing GI. This study analyzes citizens' perceptions of the relative importance of six GI practices and estimates their willingness to pay (WTP) to enhance them. To this end, the study applies two types of stated preference methods (best-worst scaling and contingent valuation) to citizen survey data collected in Portland, Oregon. We found that GI practices that are more likely to lead to private benefits (e.g., rain barrels, urban trees) received relatively higher ratings, whereas the ratings of practices that do not offer such benefits (e.g., bioswales, rain gardens) were relatively lower. However, the diversity of preferences was large, as the relative importance varied widely among respondents. Heterogeneous preferences were also found in terms of citizens' WTP for hypothetical GI enhancement. Our comparison of uniform and variable payment schemes revealed that variable payment outperformed uniform payment because of the significant variation in citizens' WTP. The difference was large when the annual household payment was small. • We find strong and widespread support for green infrastructure (GI) programs. • The willingness to pay (WTP) for green infrastructure enhancement varies significantly. • GI practices that lead to private benefits received higher ratings. • Flexibility in payment schemes can significantly improve policy cost-effectiveness. [ABSTRACT FROM AUTHOR]

Based on panel data of listed companies in China from 2006 to 2020, this study takes the establishment of automatic air quality monitoring stations as a quasi-natural experiment and uses the staggered difference-in-differences method to explore whether the establishment of monitoring stations promotes green innovation of listed companies. The empirical results show that: (1) The green innovation of companies achieves an increase of 3.5% with monitoring stations in their locations, and an increase of 2.3% with the establishment of each additional monitoring station. This conclusion is valid after a series of robustness tests and exclusive tests. (2) The heterogeneity analyses show that monitoring stations have a greater role in promoting green innovation for non-state-owned enterprises, enterprises in heavy polluting industries and enterprises in key cities for environmental protection. (3) The transmission mechanism test results show that the establishment of automatic air monitoring station has crowding-out effect rather than leverage effect on green innovation, substantial innovation rather than strategic innovation. (4) The further analyses manifest the promotion of end-to-end green innovation, independent invention and quality of green patents. • Establishing automatic air monitoring station significantly promotes the company's green innovation. • There are different effects on green innovation, due to ownership, pollution intensity and regulatory pressure. • Establishing monitoring station affects green innovation, displaying crowding-out effect and substantial innovation. • Establishing monitoring station can promote independent invention, end-to-end green innovation and quality of green patents. [ABSTRACT FROM AUTHOR]

The use of green roofs is gaining increased recognition in many countries as a solution that can be used to improve environmental quality and reduce runoff quantity. To achieve these goals, pilot-scale green roof assemblies have been constructed and operated in an urban setting. From a stormwater management perspective, green roofs are 42.8–60.8% effective in reducing runoff for 200 mm soil depth and 13.8–34.4% effective in reducing runoff for 150 mm soil depth. By using Spearman rank correlation analysis, high rainfall intensity was shown to have a negative relationship with delayed occurrence time, demonstrating that the soil media in green roofs do not efficiently retain rainwater. Increasing the number of antecedent dry days can help to improve water retention capacity and delay occurrence time. From the viewpoint of runoff water quality, green roofs are regarded as the best management practice by filtration and adsorption through growth media (soil). [ABSTRACT FROM AUTHOR]

There is an urgent requirement to examine the quality of harvested rainwater for potable and non-potable purposes, based on the type of roofing material. In this study, we examined the effect on the quality of harvested rainwater of conventional roofing materials (concrete, asphalt and ceramic tile roofs) compared with alternative roofing materials (green roof). The results showed that the ceramic tile roof was the most suitable for rainwater-harvesting applications because of the lower concentrations of leachable pollutants. However, in this study, the green roof was not suitable for rainwater harvesting applications. In addition, seasonal trends in water quality parameters showed that pollutants in roof runoff in summer and autumn were lower than those in winter and spring. This study revealed that the quality of harvested rainwater was significantly affected by the roofing material; therefore, local government and urban planners should develop stricter testing programs and produce more weathering resistant roofing materials to allow the harvesting of rainwater for domestic and public uses. [Copyright &y& Elsevier]

This paper outlines the development of a conceptual hydrological flux model for the long term continuous simulation of runoff and drought risk for green roof systems. A green roof's retention capacity depends upon its physical configuration, but it is also strongly influenced by local climatic controls, including the rainfall characteristics and the restoration of retention capacity associated with evapotranspiration during dry weather periods. The model includes a function that links evapotranspiration rates to substrate moisture content, and is validated against observed runoff data. The model's application to typical extensive green roof configurations is demonstrated with reference to four UK locations characterised by contrasting climatic regimes, using 30-year rainfall time-series inputs at hourly simulation time steps. It is shown that retention performance is dependent upon local climatic conditions. Volumetric retention ranges from 0.19 (cool, wet climate) to 0.59 (warm, dry climate). Per event retention is also considered, and it is demonstrated that retention performance decreases significantly when high return period events are considered in isolation. For example, in Sheffield the median per-event retention is 1.00 (many small events), but the median retention for events exceeding a 1 in 1 yr return period threshold is only 0.10. The simulation tool also provides useful information about the likelihood of drought periods, for which irrigation may be required. A sensitivity study suggests that green roofs with reduced moisture-holding capacity and/or low evapotranspiration rates will tend to offer reduced levels of retention, whilst high moisture-holding capacity and low evapotranspiration rates offer the strongest drought resistance. [Copyright &y& Elsevier]

Abstract: Supplemental irrigation systems are often specified on green roofs to ensure plant cover and growth, both important components of green roof performance and aesthetics. Properties of the growing media environment too can alter the assemblage of plant species able to thrive. In this study we determine how plant cover, above ground biomass and species diversity are influenced by irrigation and growing media. Grass and forb vegetative cover and biomass were significantly greater in organic based growing media but there was no effect of supplemental irrigation, with two warm season grasses dominating in those treatments receiving no supplemental irrigation. On the other hand, plant diversity declined without irrigation in organic media, and having no irrigation in inorganic growing media resulted in almost a complete loss of cover. Sedum biomass was less in inorganic growing media treatments and species dominance shifted when growing media organic content increased. Our results demonstrate that supplemental irrigation is required to maintain plant diversity on an extensive green roof, but not necessarily plant cover or biomass. These results provide evidence that planting extensive green roofs with a mix of plant species can ensure the survival of some species; maintaining cover and biomass when supplemental irrigation is turned off to conserve water, or during extreme drought. [Copyright &y& Elsevier]

This study investigates people's preconceptions of green roofs and their visual preference for different green roof design alternatives in relation to behavioral, social and demographical variables. The investigation was performed as a visual preference study using digital images created to represent eight different alternatives: gravel roof, extensive green roof with Sedums not in flower, extensive green roof with sedums in bloom, semi-intensive green roof with sedums and ornamental grasses, semi-intensive green roof with shrubs, intensive green roof planted with a lawn, intensive green roof with succulent and trees and intensive green roof with shrubs and trees. Using a Likert-type scale, 450 respondents were asked to indicate their preference for each digital image. Results indicated that respondents' sociodemographic characteristics and childhood environmental background influenced their preferences toward different green roof types. Results also showed that green roofs with a more careful design, greater variety of vegetation structure, and more variety of colors were preferred over alternatives. [Copyright &y& Elsevier]

Although vegetated green roofs can be difficult to establish and maintain, they are an increasingly popular method for mitigating the negative environmental impacts of urbanization. Most green roof development has focused on maximizing green roof performance by planting one or a few drought-tolerant species. We present an alternative approach, which recognizes green roofs as dynamic ecosystems and employs a diversity of species. We draw links between the ecological and green roof literature to generate testable predictions about how increasing plant diversity could improve short- and long-term green roof functioning. Although we found few papers that experimentally manipulated diversity on green roofs, those that did revealed ecological dynamics similar to those in more natural systems. However, there are many unresolved issues. To improve overall green roof performance, we should (1) elucidate the links among plant diversity, structural complexity, and green roof performance, (2) describe feedback mechanisms between plant and animal diversity on green roofs, (3) identify species with complementary traits, and (4) determine whether diverse green roof communities are more resilient to disturbance and environmental change than less diverse green roofs. [Copyright &y& Elsevier]

Reconciling human and non-human use of urban regions to support biological conservation represents a major challenge for the 21st century. The concept of reconciliation ecology, by which the anthropogenic environment may be modified to encourage non-human use and biodiversity preservation without compromising societal utilization, potentially represents an appropriate paradigm for urban conservation given the generally poor opportunities that exist for reserve establishment and ecological restoration in urban areas. Two habitat improvement techniques with great potential for reconciliation ecology in urban areas are the installation of living roofs and walls, which have been shown to support a range of taxa at local scales. This paper evaluates the reconciliation potential of living roofs and walls, in particular highlighting both ecological and societal limitations that need to be overcome for application at the landscape scale. We further consider that successful utilization of living roofs and walls for urban reconciliation ecology will rely heavily on the participation of urban citizens, and that a ‘citizen science’ model is needed to facilitate public participation and support and to create an evidence base to determine their effectiveness. Living roofs and walls are just one aspect of urban reconciliation ecology, but are particularly important ‘bottom-up’ techniques for improving urban biodiversity that can be performed directly by the citizenry. [Copyright &y& Elsevier]

Environmental pollution mitigation measure involving bioremediation technology is a sustainable intervention for a greener ecosystem biorecovery, especially the obnoxious hydrocarbons, xenobiotics, and other environmental pollutants induced by anthropogenic stressors. Several successful case studies have provided evidence to this paradigm including the putative adoption that the technology is eco-friendly, cost-effective, and shows a high tendency for total contaminants mineralization into innocuous bye-products. The present review reports advances in bioremediation, types, and strategies conventionally adopted in contaminant clean-up. It identified that natural attenuation and biostimulation are faced with notable limitations including the poor remedial outcome under the natural attenuation system and the residual contamination occasion following a biostimulation operation. It remarks that the use of genetically engineered microorganisms shows a potentially promising insight as a prudent remedial approach but is currently challenged by few ethical restrictions and the rural unavailability of the technology. It underscores that bioaugmentation, particularly the use of high cell density assemblages referred to as microbial consortia possess promising remedial prospects thus offers a more sustainable environmental security. The authors, therefore, recommend bioaugmentation for large scale contaminated sites in regions where environmental degradation is commonplace. • Advances in pollutant removal by bioaugmentation show promising potentials for a cleaner ecosystem. • Bioaugmentation involving microbial consortia results in multiple and effective contaminant depuration. • Recombinant DNA technology is potentially effective in biodegradation of recalcitrant pollutant. • Natural attenuation is a very slow process that often results in poor environmental decontamination. [ABSTRACT FROM AUTHOR]

Constructed ecosystems like green roofs are increasingly deployed in cities to mitigate issues associated with urbanization. To minimize the cost of green roof infrastructure, shallow growing media (substrate) for plants is often employed. Spatial heterogeneity in substrate depth has also been hypothesized to allow greater plant species diversity without adding to the weight. Stress and competition can change green roof plant communities after initial planting, but little is known about the long-term effects of spatial heterogeneity on vegetation composition and functional characteristics. Our goal was to determine how green roof plant communities and, in turn, functional plant traits, change over time in response to environmental stress and substrate heterogeneity. This four-year experiment used four substrate depth treatments: three with homogenous substrate depths of 5 cm, 10 cm, and 15 cm, and one treatment with a heterogenous substrate depth that varied between 5 cm and 15 cm (5/15 cm). The volume of the substrate in the 10 cm treatment and 5/15 cm treatment was equal. By the end of this four-year experiment, variation occurred between treatments for community composition and functional diversity, with the greatest species richness observed in the least stressful treatment (15 cm) and the greatest functional diversity and evenness observed in the most stressful treatment (5 cm). Additionally, each treatment had lower functional diversity after four years compared to the initially planted community. When the heterogenous 5/15 cm treatment was compared to the homogenous 10 cm treatment, there were no differences in the number of plant species, but the treatments contained two distinct plant communities. Furthermore, the 5/15 cm treatment supported taller species, a trait value associated with reduced stormwater runoff and substrate temperature. This finding indicates that creating green roofs with a heterogenous substrate depth could improve overall green roof function without increasing roof weight. Substrate depth can be manipulated by green roof designers to alter vegetation characteristics, but species and functional diversity showed opposite trends along the depth gradient. [Display omitted] • Substrate heterogeneity led to the formation of a taller plant community. • Very shallow green roofs can support communities high in functional diversity. • Heterogeneity improves green roof function without increasing roof weight. • After four years, all depth treatments decreased in functional diversity. [ABSTRACT FROM AUTHOR]

Despite the significance of urban landscapes, there are limiting factors like spaces and water resources to expand them across the world. These limitations necessitate the development of water-conserving strategies in vertical infrastructures such as green roofs. One water-conserving strategy is precise irrigation regimes based on the plant species' water needs. We investigated the water need of Carpobrotus edulis and Aptenia cordifolia under treatments with different soil-containing and soil-less water-absorbing substrate amenders and humic acid applications. The experiment was factorial based on a randomized complete block design with three replications and was conducted from May to September 2020. The first factor was the substrates with different green roof substrate compositions including soil-containing and soilless substrates with varying bentonite percentages. The second factor was humic acid levels (zero, 100, and 200 mg/l), which were applied as fertigation every 15 days during the experiment. Water needs were determined using the lysimetric method. The results showed that despite the soil-containing substrate with bentonite, the soilless substrate alone could not lead to optimal plant growth. The highest water use efficiency and the least evapotranspiration were obtained from the substrate containing 20%Soil +20% leca +20% perlite +20% mineral pumice +20% leaf litter plus 12% w bentonite, combined with A. cordifolia. This plant species showed a better performance compared with C. edulis. During the spring and summer months, the soil-containing substrate with bentonite and A. cordifolia can create a sustainable green roof system by creating better coverage, more water conservation, and a more aesthetic appearance. Based on the results, the application of the highest concentration level of humic acid (200 mg/l) increased the water use efficiency by about 40% after the establishment of the plants. Also, using this level of humic acid reduced the evapotranspiration rate in A. cordifolia up to 10 ml/day and in C. edulis up to 15 ml/day. [Display omitted] • Substrates and humic acid levels on green roof (GR) plants were investigated. • Humic acid (200 mg/l) increased WUE to 40% and reduced ET rates (10 ml/day in Aptenia and 15 ml/day in Carporbrotus). • Substrate 6 containing 27%v pumice +27%v Leca +27%v perlite +20%v leaf litter plus+ 12%w bentonite, combined with Aptenia showed the best plant growth performance. • Soil and bentonite-containing substrate with Aptenia had the best GR performance. • Creating sustainable green roofs depends on wise use of plant and substrate types. [ABSTRACT FROM AUTHOR]

Conventional green roofs have often been criticised for their limited water buffer capacity during extreme rainfall events and for their susceptibility to droughts when additional irrigation is unavailable. One solution to these challenges is to create an extra blue water retention layer underneath the green layer. Blue-green roofs allow more stormwater to be stored, and the reservoir can act as a water source for the green layer throughout capillary rises. An automated valve regulates the water level of the system. It can be opened to drain water when extreme precipitation is expected. Therefore, the water buffer capacity of the system during extreme rainfall events can be maximised by integrating precipitation forecasts as triggers for the operation of the valve. However, the added value of this forecast-based operation is yet unknown. Accordingly, in this study, we design and evaluate a hydrological blue-green roof model that utilises precipitation forecasts. We test its performance to capture (extreme) precipitation and to increase evapotranspiration and evaporative cooling under a variety of precipitation forecast-based decision rules. We show that blue-green roofs can capture between 70 % and 97 % of extreme precipitation (>20 mm/h) when set to anticipate ensemble precipitation forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF). This capture ratio is considerably higher than that of a conventional green roof without extra water retention (12 %) or that of a blue-green roof that does not use forecast information (i.e., valve always closed; 59 %). Moreover, blue-green roofs allow for high evapotranspiration rates relative to potential evapotranspiration on hot summer days (around 70 %), which is higher than from conventional green roofs (30 %). This serves to underscore the higher capacity of blue-green roofs to reduce heat stress. Using the city of Amsterdam as a case study, we show the high upscaling potential of the concept: on average, potentially suitable flat roofs cover 13.3 % of the total area of the catchments that are susceptible to pluvial flood risk. If the 90th percentile of the ECMWF forecast is used, an 84 % rainfall capture ratio can translate into capturing 11 % of rainfall in flood-prone urban catchments in Amsterdam. • Blue-green roofs are effective urban climate adaptation solutions. • Runoff reductions during extreme precipitation of 70–97 % were found. • This is much higher than runoff reductions found for a conventional green roof (12 %). • ECWMF precipitation forecasts used to trigger drainage increase rainfall capture. • Blue-green roofs showed overall high evaporation rates during heat events. [ABSTRACT FROM AUTHOR]

Abstract: The built environment has been a significant cause of environmental degradation in the previously undeveloped landscape. As public and private interest in restoring the environmental integrity of urban areas continues to increase, new construction practices are being developed that explicitly value beneficial environmental characteristics. The use of vegetation on a rooftop—commonly called a green roof—as an alternative to traditional roofing materials is an increasingly utilized example of such practices. The vegetation and growing media perform a number of functions that improve environmental performance, including: absorption of rainfall, reduction of roof temperatures, improvement in ambient air quality, and provision of urban habitat. A better accounting of the green roof''s total costs and benefits to society and to the private sector will aid in the design of policy instruments and educational materials that affect individual decisions about green roof construction. This study uses data collected from an experimental green roof plot to develop a benefit cost analysis (BCA) for the life cycle of extensive (thin layer) green roof systems in an urban watershed. The results from this analysis are compared with a traditional roofing scenario. The net present value (NPV) of this type of green roof currently ranges from 10% to 14% more expensive than its conventional counterpart. A reduction of 20% in green roof construction cost would make the social NPV of the practice less than traditional roof NPV. Considering the positive social benefits and relatively novel nature of the practice, incentives encouraging the use of this practice in highly urbanized watersheds are strongly recommended. [Copyright &y& Elsevier]

There is significant interest among policymakers and academics about whether or not green credit, which is a market-oriented environmental policy tool, has achieved its intended effect in improving the environment in China. This paper addresses this question from both theoretical and empirical perspectives. Using panel data from 30 provincial administrative regions of China from 2007 to 2016, we apply the fixed effect model and the gray correlation analysis method to examine the influence and its mechanism of green credit on China's environmental quality. The results show that green credit does improve China's environmental quality overall. Green credit can reduce environmental pollution through three mechanisms: improving enterprise performance, motivating enterprise innovation, and upgrading industrial structure. However, there are regional differences in the emission-reduction effect of green credit. Green credit improves the environmental quality in resource-based regions more than non-resource-based regions; the emission-reduction effect is significant in regions with developed financial markets, but not significant elsewhere. The results indicate that green credit policies should be regionally differentiated to more effectively achieve emission-reduction targets. • We examine the influence mechanism of green credit on China's environmental quality. • We use panel data from China's 30 provincial regions during 2007–2016. • We apply the fixed effect model and the gray correlation analysis method. • Green credit can reduce environmental pollution through three mechanisms. • There are some regional differences in the emission-reduction effect of green credit. [ABSTRACT FROM AUTHOR]

Municipal activities are one of the most important water users worldwide; thus, the treatment and reuse of greywater for non-potable purposes helps to reduce a remarkable amount of consumed water within urban communities. To achieve greywater reuse standards, and remove surfactants, micropollutants, organic matters, microorganisms and other pollutants various methods including physical, chemical and biological processes have been used. Treated greywater can be used on site for different purposes: carwash, toilet flushing, fire protection, green roofs, green walls, non-food irrigation etc. Among them, the use of greywater is very important in the expansion of the green roofs. Green roofs offer many benefits to urban areas such as decreasing air pollution, reducing building cooling needs, promoting mental health of habitants, noise reduction and aesthetics improvement. Therefore, this article provides an overview mainly from two aspects, the possibilities of greywater reuse by studying the characteristics and available options for greywater treatment and its benefits toward the developing green roofs. [Display omitted] • The greywater quantity and quality depend on its source. • The greywater quality is an important factor to select an efficient treatment method. • The reuse of treated greywater is nowadays necessity. • The greywater to develop green roofs is a suitable alternative. • The benefits of irrigated green roofs by greywater confirm the necessity of future studies. [ABSTRACT FROM AUTHOR]

To better analyze China's carbon neutrality target, this study investigates the effect of green innovation and investment in the energy industry on China's provincial and regional data from 1995 to 2017. Using Westerlund and Edgerton's panel cointegration test, the authors found a stable long-run relationship between CO 2 emissions and its determinants. We found that under major structural breaks at the local, regional, and global levels, such as the East Asian crises of 1997, the financial crises of 2007–2008, China's RMB exchange rate reform announced on August 11, 2015, and mild recession in 2001, CO 2 emissions, income, green innovation, renewable energy use, and energy industry investment are cointegrated. The environmental Kuznets curve hypothesis is valid. In the long run, income, environmental innovation, investment in the energy industry, and renewable energy consumption are key contributors in explaining CO 2 emissions. The empirical evidence from augmented mean group (AMG) is consistent with the estimates of CS-ARDL. Concerning practical implications, the findings suggest that there is a need to switch the Chinese economy to more sustainable sources of energy, a viable solution to abate environmental degradation. China should introduce and shift investments to green innovation. • We explore factors that help to achieve the carbon neutrality target of China. • The novel panel data econometric tools were used for empirical analysis. • It confirmed the existence of the EKC hypothesis for provincial data of China. • Investment in energy and technological innovation helps to reduce emissions. • Renewable energy consumption also helps to achieve zero emissions target. [ABSTRACT FROM AUTHOR]

Green roofs are widely considered as a promising nature-based solution for urban stormwater management. In this study, the stormwater retention and detention performance of 6 green roof modules with different types and depth of substrates at Beijing, China was investigated through 3-year continuous monitoring. The Hydrus-1D was applied to further explore the stormwater management performance of green roofs under extreme storms. The average event-based stormwater retention and detention rates of the green roofs with 10 cm substrates ranged between 81% and 87%, and 83%–87%, respectively; and the average time delays in runoff generation and peak discharge ranged between 82 and 210 min, and 63–131 min, respectively. Green roofs with 15 cm depth of substrates offered higher stormwater retention and peak runoff attenuation rates than those with 10 cm substrates. However, due to the high frequency (55 out of total 92) of light rainfall events (<10 mm) and short antecedent dry weather periods (3.8 days in average), no significant difference was found on stormwater control performance of those green roofs. The Hydrus-1D simulations revealed that green roof stormwater retention rate decreases exponentially with return periods of extreme storms but increases with substrate depth. There exists a critical depth of substrates and further increases in substrate depth beyond this critical value could not bring much improvement in stormwater retention performance of green roofs. The application of extensive green roofs with 10–15 cm substrates provides promising stormwater retention and detention performance in highly urbanized area of Beijing. [Display omitted] • Rainfall-runoff processes of 6 green roofs (GR) were monitored in 2017–2019. • The GR provided prominent hydrologic performance under 92 natural rainfall events. • Responses of GR under extreme storms were simulated via Hydrus-1D. • Impacts of types and depth of substrates on the hydrologic performance were analyzed. • Stormwater retention and detention mechanisms of GF were revealed. [ABSTRACT FROM AUTHOR]

The pilot carbon emission trading scheme in Guangdong Province (GD ETS) of China has fulfilled seven compliance periods, and its potential impact on regulated firms has drawn increasing attention. This article empirically investigated the impact of the ETS on firm behaviors and competitiveness (i.e., cost competitiveness and green competitiveness) by surveying all power firms in the GD ETS. Low-carbon management, carbon asset transactions, and energy saving and emission reduction technology were identified as firm behaviors. The relationships among the ETS, firm behaviors, and firm competitiveness were tested by using bootstrap multiple mediation analyses. The results showed that the GD ETS has a positive impact on firm behaviors. The three examined firm behaviors actually reflect the depth of firm participation in the ETS. The more the firm participates, the greater the mediating effects that the firm behaviors exert on firm competitiveness are. Both carbon asset transactions and energy saving and emission reduction technology have a mediating effect on the relationship between the GD ETS and cost competitiveness, while only the latter mediates the relationship between the GD ETS and green competitiveness. Implications for policy makers and firm operators were discussed. • The ETS has a positive impact on firm behaviors of management, transaction and technology. • The more the firm participates, the greater the mediating effects that the firm behaviors exert on firm competitiveness are. • Technology activity mediates the relationship between the ETS and firm competitiveness. [ABSTRACT FROM AUTHOR]

Given that improving urban ecological environment requires a clear recognition of the urban ecological elements, investigating the ecosystem service capabilities of urban green-blue infrastructures (UGBIs) becomes ever important. This study aims to reveal and compare the synergistic ecosystem service ability of UGBIs with different characteristics and the relationship with human demand in Wuhan city. It was found that the climate regulation service and water regulation service value of lake-type parks both reached the highest over the other UGBIs. Nature-type parks revealed the most capable cultural service, and green-type parks demonstrated the greatest exercise cultural service value. The analysis showed that the ecosystem services delivered by the UGBIs were influenced by the park area, the total value of the normalized difference vegetation index and normalized water body index, and the distance from the city centre. Furthermore, a significant spatial phenomenon was found that the ecological capacity of lake-type parks in the city centre was higher than that of the other UGBIs at the same location. Regarding the relationship with the human activity intensity, the high-demand and high-supply regions were mainly concentrated in highly developed areas in terms of regulating services. Nevertheless, a severe environmental inequality occurred in small urban centres, which requires urgent attention from the government. This work answered the question of where and how to optimize the green-blue infrastructures in Wuhan, and it contributes to the construction of the existing blue-green space. The ecosystem services capabilities of blue-green infrastructures with different characteristics and the spatial matching relationship with human activities. [Display omitted] • The ecosystem service capabilities of green-blue infrastructures are investigated. • The ecological capability of lake-type UGBI in the city centre was the highest. • There existed a spatial mismatching relationship of UGBIs with human activities. • Regulating services in highly developed areas concentrated more matching regions. • A severe environmental inequality occurred in small urban centres. [ABSTRACT FROM AUTHOR]

Urbanisation and climate change collectively impose the threat of urban flood. The impervious transformation and changes in local climatic conditions increase the risk of frequent pluvial flooding in Kathmandu. Therefore, this study aims to assess the integrated impact of urbanisation and climate change on pluvial flooding in Kathmandu Metropolitan City, using the Personal Computer Storm Water Management Model. The future daily rainfall from three Regional Climate Models under two Representative Concentration Pathways (RCPs) and the observed daily data has been disaggregated to hourly series using temporal rainfall disaggregation. The result shows that the combined impact on pluvial flood is likely to intensify with relatively more contribution from climate change. The CNRM-CM5-CSIRO-CCAM under the RCP 4.5 scenario projects the maximum increase (60–90%) in flood volume for current (75%) and extreme (90%) imperviousness, under a 2-year and 20-year return period (RP) with the extent of the flood area increasing more than the depth. For a 2-year RP, areas with a depth of 0.10–0.25 m are likely to expand while those from 0.25 to 0.40 m in depth are projected to have more velocity, and these trends are expected to be magnified for higher RPs. The study shows that even though urbanisation contributes less to urban pluvial flood, it can be a catalyst for exaggerating other factors and implementing management measures. For instance, the application of small-scale rainwater harvesting, and overflow storage reduced the runoff, thereby reducing the flood volume by 20–35%. Furthermore, the findings highlight the need for planning management strategies such as evaluation and upgrading of conventional drainage systems with low impact measures (rainwater harvesting and green roofs); technical and financial assistance to urban dwellers in adopting the management measures or a combination of them based on the location, requirements, and availability of information and resources to reduce the effects of pluvial flood in Kathmandu. Image 1 • We modelled the combined impact of climate change and urbanisation on flooding. • Climate change is likely to be responsible for urban flooding in Kathmandu. • The flooding extent is projected to increase more than the flooding depth. • Flooding areas with depth between 0.10 and 0.40 m are expected to be more in future. • Harvesting rainwater and underground runoff storage can reduce 20–35% flood volume. [ABSTRACT FROM AUTHOR]