Types Of Green Infrastructure Research Articles

Projected performance of green infrastructure strategies for flood mitigation in the Ganges-Brahmaputra-Meghna delta

Background: The Ganges-Brahmaputra-Meghna (GBM) delta – the world’s most populous river delta – faces heightened susceptibility to the rise in flooding disasters due to climate change, impacting millions annually. Current flood management strategies are unsustainable and ineffective, and resilient flood management is needed. A promising alternative is the strategic implementation of green infrastructure (GI) applications, which have proven effective in flood management in other regions. Methods: An analysis of the region’s past and future vulnerability to flooding is conducted. Then, green infrastructure performance metrics from regions with similar climatic conditions are extrapolated for the GBM. Green roofs, permeable pavements, and rain gardens were identified as the most suitable GI types for the GBM. Finally, computer simulations were employed to analyze the performance of different implementations of GI within a model city. Results: The simulations showed that 0% green rooftop coverage, 100% permeable pavement coverage, and 40% rain garden coverage were the most feasible GI layout. This configuration resulted in the most preferable balance between cost effectiveness and reduced runoff. Green rooftops were minimized due to high installation costs relative to their retention capacity, whereas permeable pavements and rain garden coverage were maximized. Conclusions: The studies show GI’s potential for flood mitigation and resilience in the GBM region. GI initiatives align with the region's flood mitigation policies and are thus feasible to implement with aid from government incentives. Furthermore, the computer program developed for this analysis could serve as a valuable tool for assessing GI implementation limits and offering guidance to policymakers.

Spatial allocation of bioretention cells considering interaction with shallow groundwater: A simulation-optimization approach

Green infrastructure (GI), as one type of ecological stormwater management practices, can potentially alleviate water problems and deliver a wide range of environmental benefits in urban areas. GIs are often planned and designed to reduce runoff and mitigate pollution. However, the influence of GI on groundwater hydrology and that of shallow groundwater on GI performance was seldom considered. This study utilized a calibrated surface-subsurface hydrological model, i.e., Storm Water Management Model coupled with USGS's modular hydrologic model (SWMM-MODFLOW) to consider the interaction between GI and groundwater into the process of GI planning. The optimal implementation ratio, aggregation level and upstream-downstream location of bioretention cells (BC, one type of GI) under different planning objectives and hydrogeologic conditions was explored. The consideration of groundwater management exerted a significant impact on the optimal spatial allocation of BCs. The results showed that when groundwater management was more concerned than runoff control, BCs were recommended to be allocated more apart from each other and more upstream in the catchment because more-distributed and upstream BCs can result in lower groundwater table rise which is beneficial. BCs were overall recommended to be allocated in areas of deeper groundwater tables, coarser soils, and flatter topographies. However, the spatial features of BCs are related to each other, the choice of them are affected by various hydrogeologic factors simultaneously. The exact location of BCs should be determined by considering the trade-off between runoff control efficiency and groundwater impact. The findings obtained in this study can provide guidance on GI planning in shallow groundwater areas.

A transferable approach to assessing green infrastructure types (GITs) and their effects on surface urban heat islands with multi-source geospatial data

Urban green infrastructure (GI) is essential for mitigating surface urban heat islands (SUHIs) and strengthening urban resilience to climate change, thereby contributing to the achievement of sustainable development goals in urban areas. A ‘green infrastructure types’ (GITs) scheme was recently developed to examine the role of amount, composition, and configuration of GI in providing effective thermal cooling in Australia. However, the GIT scheme has not been applied to an urban environment in other countries, so its general suitability for SUHI assessment needs to be further investigated. Taking the urban core area of Beijing as a case study, a multi-level classification method was developed in this study for GIT mapping using bi-seasonal high-resolution Gaofen-1 satellite imagery, time-series Sentinel-2 A/B and SDGSAT-1 satellite data, and open vector datasets. The time series of 30 m land surface temperature (LST) data was created by blending high temporal resolution MODIS and Landsat data. Statistical analysis was performed to identify factors that may influence the cooling effect of GI. The results demonstrate significant LST differences among the GITs in summer. The aquatic GITs with a water fraction >50% (5.6–7.6 °C) and pervious GITs with a high tree fraction (5.4–5.6 °C) provided the largest cooling effect. The cooling capacity of mixed and pervious GITs was found closely related to the proportion of pervious surface and woody vegetation. Increasing the area of irrigated grass from low (28%) to medium (61%) in mixed surfaces produced only a marginal effect on surrounding LSTs. The GIT mapping approach combined with SUHI analysis provides a transferable and promising framework for examining the cooling effect of GI at the neighborhood level in a consistent manner.

A valuation study to identify the determinants of the demand for time spent outdoors among users of hospital facilities, their willingness-to-pay for green infrastructure improvements, and the implications for planning

ABSTRACT Green infrastructure has been promoted as an urban planning tool for the achievement of health and environmental policy objectives. The capacity of economic valuation methods to estimate monetary benefit values for intangible goods, such as mental health and wellbeing, renders them useful in justifying green infrastructure interventions and guiding their implementation. In this case study we used stated preference methods to elicit cross-sectional data on the preferences of staff (n=118), visitors (n=88), and inpatients (n=35) of Musgrave Park Hospital in Northern Ireland, for improvements in the hospital’s outdoor grounds. To our knowledge, this is the first paper to use the contingent behavior method to examine the demand for time spent on the improved outdoor grounds of a hospital and the first to use the contingent valuation method to obtain the respective willingness-to-pay values. The results show that the three hospital user groups differed in their preferred types of green infrastructure and their motivations for using the outdoor grounds, an important input for planning the transformation of the outdoors. Other findings suggest that to maximize health and well-being benefits, complementary measures to address the issues of sedentary lifestyles and inadequate use of the outdoors as a stress-coping mechanism are needed.

Modeling benefits and tradeoffs of green infrastructure: Evaluating and extending parsimonious models for neighborhood stormwater planning

Green infrastructure is often proposed to complement conventional urban stormwater management systems that are stressed by extreme storms and expanding impervious surfaces. Established hydrological and hydraulic models inform stormwater engineering but are time- and data-intensive or aspatial, rendering them inadequate for rapid exploration of solutions. Simple spreadsheet models support quick site plan assessments but cannot adequately represent spatial interactions beyond a site. The present study builds on the Landscape Green Infrastructure Design (L-GrID) Model, a process-based spatial model that enables rapid development and exploration of green infrastructure scenarios to mitigate neighborhood flooding. We first explored how well L-GrID could replicate flooding reports in a neighborhood in Chicago, Illinois, USA, to evaluate its potential for green infrastructure planning. Although not meant for prediction, L-GrID was able to replicate the flooding reported and helped identify strategies for flood control. Once evaluated for this neighborhood, we extended the model to include water quality through the representation of dispersion and settling mechanisms for two pollutant surrogates—total nitrogen and total suspended solids. With the extended model, Landscape Green Infrastructure Design Model-Water Quality (L-GrID-WQ), we examined benefits, costs, and tradeoffs for different green infrastructure strategies. Bioswales were slightly more effective than other green infrastructure types in reducing flooding extent and downstream runoff and pollution, through increased infiltration and settling capacity. Permeable pavers followed in effectiveness and are suggested where spatial constraints may limit the installation of bioswales. Although green infrastructure supports both flooding and pollution control, small tradeoffs between these functions emerged across spatial layouts: strategies based on only curb-cuts better controlled pollution, while layouts that followed the path of water flow better controlled flooding. By illuminating such tradeoffs, L-GrID-WQ can support green infrastructure planning that prioritizes unique concerns in different areas of a landscape.

Interdisciplinary Perspectives on Green Infrastructure: A Systematic Exploration of Definitions and Their Origins

Green Infrastructure (GI) is rooted in ecology and cuts across multiple disciplines, including landscape architecture, environmental sciences, planning, policy, and engineering. Likewise, the definition of this concept also cuts across disciplines, which creates ambiguity around what GI is and what makes up GI in practice—for example, mistaking bioswales for regular tree planters or green space within communities in which they are installed. We undertook a systematic literature review of 38 peer-reviewed articles for this study using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) method to identify and synthesize the different disciplinary definitions of GI in the literature. This study also presents the types of GI systems mentioned in the peer-reviewed articles while identifying other benefits apart from the primary benefit of GI installation, which is stormwater management. The analysis revealed three clusters of GI definitions: (I) Interconnected natural areas and other open spaces, (II) Strategically planned natural and semi-natural areas, and (III) Decentralized systems and techniques. However, we got rid of the third cluster during the analysis because GI is known to be a decentralized system, and the definition region could not be tracked. These clusters represent a spectrum, one of which employs the structure of natural systems already in place to support human goals (bio-inclusivity). The other includes living systems as components within engineered solutions to achieve objectives (bio-integration). This review points to the need for an encompassing definition that cuts across disciplines with a consensus on the adoption and concise categorization of GI types and the multiple benefits they provide to humans and ecosystems. A consensus definition helps clear misconceptions and improve the understanding of GI, potentially improving receptivity towards these solutions within communities from a community member perspective.

Potential Impacts of Green Infrastructure on NOx and PM10 in Different Local Climate Zones of Brindisi, Italy

This study delves into Green Infrastructure (GI) planning in Brindisi, Italy, evaluating its influence on urban air quality and thermal comfort. Employing an LCZ-centered Geographic Information System (GIS)-based classification protocol, the prevalence of LCZ 6 (Open low-rise) and LCZ 2 (Compact mid-rise) is highlighted. Despite generally low PM10 levels in Brindisi, intermittent NOx spikes surpassing WHO and EU standards pose health risks. Within LCZ 2, diverse GI interventions (green walls, hedges, trees) were tested, with green walls emerging as the most effective, albeit falling short of expectations, while trees exhibited adverse air quality impacts. LCZ 6 demonstrated enhanced air quality attributed to wind patterns, GI, and urban canyon improvements. Thermal comfort analysis consistently revealed positive outcomes across various GI types, reducing discomfort by a minimum of 10%. The study emphasized GI’s favorable comfort impact on sidewalks but cautioned against trees in street canyons with aspect ratios exceeding 0.7, heightening pollutant levels and implying increased exposure risks. Conversely, street canyons with lower aspect ratios displayed variable conditions influenced by prevailing regional wind patterns. In conclusion, the integrated assessment of LCZ and GI holds promise for informed urban planning, guiding decisions that prioritize healthier, more sustainable cities. This underscores the crucial need to balance GI strategies for optimal urban development, aligning with the overarching goal of promoting urban well-being and sustainability.

A lack of focus on data sharing, stakeholders, and economic benefits in current global green infrastructure planning

Green infrastructure (GI) is increasingly popular in solving urban environmental challenges and enhancing ecosystem services. Yet the research status and challenges of GI planning have not been comprehensively benchmarked to date. We explored the GI types, actions, goals, and spatiotemporal characteristics of GI planning cases worldwide based on the available literature. The challenges of GI planning were also investigated by the cases included in this manuscript. Additionally, the urban governance solutions to address these challenges were proposed. We found that multi-type GI planning is the most popular. Data sharing, stakeholder participation, economic benefits and research funding for GI planning research were generally inadequate, although they have improved trend over time. Multiple-goal GI planning frequently has higher levels of data sharing, stakeholder participation and economic benefits than GI planning that just takes into account one purpose. We conclude that the future transformation of GI planning requires efficient data sharing mechanisms, effective co-design among stakeholders, systematic business models, and available research funding.

Enhancing Access to Urban Hill Parks: The Montjuïc Trail Masterplan and the 360° Route Design in Barcelona

The 2030 United Nations Sustainable Development Goals (SDGs) include ensuring universal and safe access to green spaces. Some cities feature extensive green areas on hills or elevated terrains integrated into the urban landscape. In such cases where the benefits for users are highly pronounced (e.g., views, isolation, etc.), it is challenging and particularly complex to design strategies to ensure accessible and spatial routes due to multiple slopes and a challenging topography. In Barcelona, the iconic Montjuïc mountain has been the focal point of a trail masterplan aimed at rethinking its various access points and internal network of routes. Furthermore, the city has committed to implementing an initial project from this plan, the so-called 360° route. This study presents an in-depth analysis of the Montjuïc mountain case, encompassing both the plan and the 360° project in hilly urban parks. The analysis reveals the values and transferability of the set of strategies proposed in the plan, such as activating inherent location characteristics by connecting the surrounding urban fabric with elements of recreational potential within the underlying traces of heritage value. Additionally, a quantitative assessment of the impact of the proposed accesses on the population is presented. The study highlights the improvements in quality of life for the diverse users of this type of green infrastructure.

Which Plant Species for Green Roofs in the Mediterranean Environment?

In recent years, owing to intense urbanization and global change with the consequent extreme climate effects, interest in green roofs, even extensive ones, in the Mediterranean environment has increased. To this end, the choice of plant species is crucial because, owing to the identification of the most suitable plants, it will be possible to expand this type of green infrastructure and increase its ecosystem services in the urban environment. In this context, the objective of the review, through a critical analysis of some of the references on the topic, is to identify suitable criteria for plant species selection that are simple to apply and able to respond to the need to have plants capable of surviving, ensuring a suitable aesthetic effect, and providing essential ecosystem services. We also investigated whether, and to what extent, associations of different species can better adapt to the difficult environmental conditions of Mediterranean green roofs. Two possible strategies to identify the plant idiotype were analyzed: the analysis of plants present in habitat analogues or the identification of morpho-functional characters capable of discriminating the response to abiotic stress, and in particular to drought stress. The use of plant communities, rather than a single species, seems capable of improving aesthetic effects, plant survival, and ecosystem services.

Exploring socio-ecological inequalities in heat by multiple and composite greenness metrics: A case study in Belfast, UK

In light of pressing environmental and social justice challenges, levels of interest in green infrastructure as a possible solution have increased markedly for reasons related to both climate change adaptation and enhancing quality living environments. This study explores how green infrastructure influences the urban heat island effects experienced by communities across the socio-economic strata found in Belfast. To avoid scale effects and obtain accurate results, we devise multiple and scale-composite greenness metrics to assess the distribution of green infrastructure based on each residential unit. The results indicate that despite widespread recognition that green infrastructure significantly contributes to the mitigation of heat island intensity, socio-economically deprived communities are exposed to greater urban heat. Further examinations identified the close correlations between green infrastructure distribution and socio-economic factors, which relate to two major spatial patterns: that the suburbs are better catered for than the inner city, and that south and east Belfast are better than west and north. Moreover, our findings identified a tendency that communities with higher proportions of female- and ageing- populations have greater greenness and are less exposed to heat, which suggests the distributional and environmental injustice in GI provision and related heat adaptation are driven by the underlying socio-economic dynamics and the vulnerable groups may change based on local context. Overall, we found that there is a need to incorporate and prioritise different types of green infrastructure in plans for heat adaptation and to integrate green infrastructure development with environmental justice in areas that suffer socio-ecological deprivation in mitigating urban heat island effects.

Biochar Benefits Green Infrastructure: Global Meta-Analysis and Synthesis.

Urbanization has degraded ecosystem services on a global scale, and cities are vulnerable to long-term stresses and risks exacerbated by climate change. Green infrastructure (GI) has been increasingly implemented in cities to improve ecosystem functions and enhance city resilience, yet GI degradation or failure is common. Biochar has been recently suggested as an ideal substrate additive for a range of GI types due to its favorable properties; however, the generality of biochar benefits the GI ecosystem function, and the underlying mechanisms remain unclear. Here, we present a global meta-analysis and synthesis and demonstrate that biochar additions pervasively benefit a wide range of ecosystem functions on GI. Biochar applications were found to improve substrate water retention capacity by 23% and enhance substrate nutrients by 12-31%, contributing to a 33% increase in plant total biomass. Improved substrate physicochemical properties and plant growth together reduce discharge water volume and improve discharge water quality from GI. In addition, biochar increases microbial biomass on GI by ∼150% due to the presence of biochar pores and enhanced microbial growth conditions, while also reducing CO2 and N2O emissions. Overall results suggest that biochar has great potential to enhance GI ecosystem functions as well as urban sustainability and resilience.

Evaluation of an Incentive Programme for Increasing Green Infrastructure on Vineyards

Wine grape ecosystems with low species richness and reliance on agrichemicals have weak resilience to environmental impacts. Increasing biodiversity through green infrastructure (GI) not only helps mitigate some of these impacts but can provide additional benefits to growers and the public. Despite this, many vineyards have limited GI. While scholars suggest incentive programmes may help to encourage GI implementation, few studies have evaluated their effectiveness. We surveyed winegrowers and their vineyards in the Waipara Valley sub-region, New Zealand, to evaluate an incentive programme aimed at increasing GI on vineyards, particularly indigenous vegetation. The results indicated the programme was effective in encouraging growers to plant indigenous plants in areas incapable or unsuitable for growing grapes, largely in support of nature conservation, aesthetics, branding, and sales. It was less successful in encouraging growers to plant them in productive areas. While substantial GI, primarily in the form of inter-row cover crops, was managed in these areas, most were exotic plants seen by growers to provide superior services (especially erosion control, weed suppression and pest regulation) at lower management complexity and cost. Growers identified six GI enablers: (1) promoting GI types that provide greater grower services than disservices and costs of implementation and management; (2) implementing GI where biophysical conditions support success; (3) providing assistance with plant selection and design; (4) providing GI implementation and/or management funding; (5) developing GI certification policies and regional association programmes; and (6) providing government GI regulations, strategies, and incentives. They also identified five barriers: (1) insufficient grower appreciation for indigenous GI services; (2) grower concerns that some GI disservices were greater than their services; (3) grower belief that costs of GI implementation and/or management were greater than those of alternative practices; (4) harsh and remote GI growing conditions; (5) lack of grower knowledge regarding how to design plantings, especially those that could provide multiple services; and (6) lack of sufficient financial resources for GI implementation and/or management. Twenty recommendations for improving GI implementation are provided.

Catchment-scale life cycle impacts of green infrastructures and sensitivity to runoff coefficient with stormwater modelling

Urban green infrastructure (GI) has been widely used in sponge city construction to manage hydrological processes. While studies on environmental benefits of GI from the perspective of whole life cycle assessment (LCA) have been reported in recent years, few have explored and compared the environmental performance of different GIs within a single catchment, which is directly linked to catchment-scale hydrological control. This study focuses on a Sponge City pilot project in Shenzhen, China, including three typical types of GI: permeable pavement, green roof, and sunken green space. By collecting hydrological data, land use, and life cycle inventory of GI and employing SWMM (Storm Water Management Model)-based stormwater modelling, we have revealed the environmental impacts at different stages of the life cycle of the GI scenario and three GIs through comparative and sensitivity analyses. Notably, we have disclosed, for the first time, the effect of the runoff coefficient in LCA. Our findings indicate that over the 30-year life cycle, the total environmental impact of the GI scenario is 24 % smaller than that of the hypothetical grey scenario. Permeable pavement exhibits the largest environmental impact per unit area, being 1.8 times and 7.6 times greater than that of the green roof and sunken green space, respectively. The operation stage of the three GIs significantly mitigates eutrophication and climate change. Furthermore, sensitivity analysis demonstrates that an increase in surface runoff undermines the environmental benefits of GIs. These results highlight the importance of embedding stormwater modelling into LCA, enabling catchment-scale integrated evaluation and equivalent assessment of different GIs within a single catchment whereby the influence of external factors such as climate change can be described, which aids in understanding the dynamic environmental performance of GIs. The proposed research framework and results are anticipated to provide valuable guidance for future GI construction and carbon-neutral policies.

Green in grey: ecosystem services and disservices perceptions from small-scale green infrastructure along a rural-urban gradient in Bengaluru, India

ABSTRACT Ecosystem services provided by green infrastructure are often discussed for their potential to address the societal challenges of urbanization. However, green infrastructure, particularly small-scale types (e.g. trees), is vulnerable to loss through urbanization and is often passed over during scientific investigations. Studies on the perceptions of ecosystem services and disservices (hereafter called ecosystem (dis)services) dynamics along the rural-urban gradient are particularly rare in the literature. Therefore, this study assessed the perceived importance of ecosystem (dis)services associated with small-scale green infrastructure along a rural-urban gradient in Bengaluru, India. Based on photos of the five most common types of small-scale green infrastructure and the three most common tree species associated with them, we conducted a photo-elicitation survey of 649 residents from 61 towns in Bengaluru. We found significant differences in the perceptions of all ecosystem (dis)services among the types of green infrastructure. The most appreciated services were air/climate regulation from platform trees and aesthetic values from farm trees. Regulating services were most appreciated in urban areas while provisioning and cultural services were most appreciated in transitional areas, and disservices were most strongly perceived in rural areas. Gender, age, education, caste, and income from agriculture significantly affected the use and valuation of the ecosystem (dis)services within the local communities. Our study reveals the crucial role of small-scale green infrastructure as a multifunctional element, which is highly relevant for the supply of provisioning, regulating, and cultural ecosystem services in Bengaluru.

Identification of High-Value Land for Green Infrastructure in Urban Fringe Areas: A Case Study of Zhengzhou, Henan Province, China

Urban fringe is the most active and complex space in which land and ecology change under the influence of urban expansion. Green infrastructure (GI) in urban fringe areas consists mostly of diversified, small-scale, and scattered green spaces, which simultaneously fulfill the functions of ecological maintenance and urban–rural services. Assessing GI land’s value can promote its effective use. Therefore, the purpose of this study was to determine various GI patches’ land value, specifically identifying GI lands with potential for public goods output in the urban fringe, which is oriented toward public welfare output. First, based on a combination of remote sensing technology, big data analysis, and artificial intelligence, we determined that Zhengzhou is divided into core area, edge area, and outer edge area. Second, we found that morphological spatial pattern analysis can accurately identify GI types that play important roles in ecological protection, and the GI lands in the fringe area of Zhengzhou can be characterized as small and fragmented, having poor connectivity, representing a single land type, containing a high proportion of farmland, and a lacking a purely natural landscape. Third, we constructed an evaluation system from ecological maintenance and urban–rural services public goods and identified the high-value GI lands of the edge district of Zhengzhou, including Xianghu Ecological Wetland Park, Die Lake Park, Xiliu Lake Park, Changzhuang Reservoir, Jiangang Reservoir, and greenways along some rivers and roads. Our results highlight the value of microhabitats in the urban fringe and suggest effective ways of protecting and utilizing them, providing a basis for GI network planning and construction and contributing to sustainable urban development.

Influence of Urban Green Spaces on Quality of Life and Health with Smart City Design

Publicly available green spaces are great places for people to relax. Currently, the deficiency of such spaces is decreasing daily, especially in urban regions. Urban green spaces (UGSs) have become a topic of great importance in enhancing life expectancy and health. To overcome these issues, the current research highlights the importance of UGSs for the residents’ living quality and urban health. UGSs are relevant for analyzing and investigating better urban lifestyles and development. To perform the experimental work, a green laboratory (GL) in a smart city (SC) area was involved in the investigation. The GL was made of wood, and different types of green infrastructure were analyzed. The research investigation resulted in upgrading the locality. Semi-structured interviews were conducted to enhance the quality of the research. Interviews with residents, occupants of offices, and government experts were conducted. Special survey questions, i.e., quantitative and qualitative, were developed while considering the current demands of the residents. A total of 500 responses were recorded, and by using the MAXQDA software, an analysis was carried out. The results showed that there was a dire requirement for UGSs in terms of size and quantity because of security and opportunities. The proposed research results will provide an opportunity for open spaces to be created in this local district. To fully improve residents’ living style and health, the necessity of deploying UGSs became more apparent. Finally, it became clear that green spaces are necessary to improve the country’s economy.

Understanding Urban Green Spaces Typology’s Contribution to Comprehensive Green Infrastructure Planning: A Study of Canberra, the National Capital of Australia

The urban densification agenda for the Australian Capital Territory announced in 2012 as well as the climate-related impacts (such as flood and rising temperature) have made the role of green infrastructure in this city more critical than at any other time. The Living Infrastructure Plan for Canberra was proposed by the local government in 2019 and it is currently being developed. However, there is a lack of understanding of the variety of urban green infrastructure characters, associated urban green space types, and their contributions to the green infrastructure plan. Therefore, this research aims to study the existing types of urban green infrastructure and green spaces in Canberra and investigate their potential sociocultural and ecological contributions that need to be considered in developing green infrastructure plans. To achieve this, we employed a socioecological approach and a mix of methods including a literature review, a review of policy documents, semi-structured interviews with experts, geospatial data, and field observation. Ten main urban green infrastructures were identified in Canberra and associated green spaces and their ecosystem services were discussed. Finally, a framework was delineated to suggest recommendations for the identified urban green infrastructure types with the aim of improving the green infrastructure planning practice by enhancing, preserving, and reinforcing green spaces. The findings provide a foundation for coordinating green infrastructure decision making and suggest a framework for designing high-quality and multifunctional green spaces. The study concludes that further investigation is required to comprehend the diversity of urban green infrastructures and their ecosystem services, co-benefits, synergies, and trade-offs.

A multi-objective decision-making framework for implementing green-grey infrastructures to enhance urban drainage system resilience

Green-grey infrastructures implementation for addressing urban flood damages and urban drainage system’ (UDS) resilience (respectively) needs comprehensive evaluation under various planning and design influencing factors. In this paper, a multi-objective decision-making framework is developed for the optimization of green-grey infrastructures to understand the trade-off between benefits and retrofit costs under various design configurations, rainfall intensities, and system performance indicators. In the developed framework, the grey infrastructure locations are optimally determined by using Analytic Hierarchy Process (AHP) method with three defined indicators (e.g., flood volume and flood duration of flooding nodes, sensitivity of flooding nodes) and maximum percentage of each type of green infrastructure (GI) in each sub-catchment based on land-use analysis as a preliminary step of the multi-objective optimization process, followed by decision-making procedure. The application results reveal that optimal designs of grey infrastructure are more cost-effective and may have a significant influence on the reduction of flood damages and outlet peak flow compared to GI from their individual evaluations, while GI improves UDS’ functionality performance indicators (e.g., resilience, reliability, and sustainability) better than grey infrastructure. However, a combined implementation of both infrastructures boosts their advantages because of the synchronization effect compared to individual scenarios, providing the most cost-effective optimal UDS designs. Moreover, the cost-effectiveness of coupled green-grey infrastructures designs could be enhanced from lower to higher design storms because of higher rate of utilization of stormwater infiltration and storage capacities of both infrastructures. The framework presented in this study can be conveniently generalized to other case-studies for optimal implementation of green-grey infrastructures as long as including their local economic parameters, climatic patterns, urban development plans and green-grey infrastructures design guidelines.

Effects of green infrastructure on the dispersion of PM2.5 and human exposure on urban roads

Urban green infrastructure (GI) has been widely demonstrated to effectively improve air quality in the built environment. However, due to the lack of comparative studies of the effects of different GI forms on PM2.5 dispersion, optimal GI designs suitable for different urban road types currently remain unclear. In this study, we adopted different roadside GI types in Hangzhou city as case studies and used the ENVI-met model to compare the effects of the different GI forms on PM2.5 dispersion and human exposure to PM2.5. The results indicated that 1) In open roads, the concave-shaped GI type could effectively reduce PM2.5 aggregation and human exposure on motorways, and the all-tree GI type performed the best in terms of sidewalk PM2.5 purification. 2) In street canyons, green roof and green screen were highly conducive to PM2.5 concentration reduction under commuter exposure compared with traditional green solutions. 3) There were trade-offs in the GI-PM2.5 interaction. GI types which can reduce pedestrian exposure tend to increase exposure in motorways. The same GI type deployed along the two different road types could yield completely opposite dispersion effects. Novel GI types had better environmental performance and relatively high economic cost. All decision-making should be based on the trade-offs between the advantages and disadvantages of GI. Our study also highlights the importance of comprehensive consideration of GI and road types and local wind conditions in future urban road planning and GI applications.