Knowledge, attitudes, intentions, and behavior related to green infrastructure for flood management: A systematic literature review

A quantitative review of nature-based solutions for urban sustainability (2016-2022): From science to implementation

Nature-based solutions (NBS) have great potential for achieving urban sustainability. While several reviews have comprehensively examined NBS, few have focused on its role in addressing urban sustainability challenges. Here we present a systematic review of 142 case studies selected from English papers published in SCI journals (i.e., indexed by Web of Science) during 2016-2022, whose titles, abstracts or keywords contain both urban-related terms and NBS-related terms. Using multiple methods, including statistical analysis, deductive content analysis, and inductive content analysis, we found that: (1) NBS have primarily been utilized to address urban flooding (43 %) and heat stress (21 %), with green roofs (24 %) and urban forests (16 %) being the most extensively studied NBS for tackling these challenges. (2) The ecosystem services (ES) capacity of NBS has been heavily researched (57 %), while studies addressing ES flows (7 %) and ES demand (18 %) are limited. (3) Most studies involved at least one NBS implementation process (83 %), but primarily focused on selecting and assessing NBS and related actions (66 %), with fewer studies on designing and implementing NBS and transferring & upscale NBS. We suggest that future research should contribute to the establishment of a checklist to assist in identifying which NBS types are effective in addressing specific urban sustainability challenges in varying contexts. Integrating the science and practice of NBS for urban sustainability is also crucial for advancing this field.

Modeling the impact of future rainfall changes on the effectiveness of urban stormwater control measures

The convergence of urban expansion, deteriorating infrastructure, and a changing climate will escalate the risks of stormwater pollution and urban flooding in the coming decades. Using outputs from an ensemble of global climate models to drive a high spatial resolution stormwater model, we analyzed climate change impacts on urban stormwater runoff and control measures for 23 cities across the United States. Runoff model outputs for two future emissions scenarios ending in 2055 were compared against a historical scenario to assess changes. All cities showed increases in average annual stormwater runoff, with changes up to 30% over the next 30 years due to a greater frequency of high intensity storm events. Runoff model outputs showed substantial variation across cities with untreated stormwater runoff increasing by as much as 48%. Patterns of future runoff impacts within cities will affect the performance of distributed treatment strategies such as Green Stormwater Infrastructure (GSI) to meet municipal water quality improvement and runoff reduction goals. Results indicate that adoption of adaptable design standards and decision support tools that readily accommodate projected precipitation changes are critical for supporting more resilient designs of stormwater control measures.

Exploring the Factors That Influence Stakeholder Participation in Decision-Making for the Moat System Restoration Project in Tianchang City, China

The driving factors have a critical effect on shaping stakeholder behavior toward participating in decision-making for river restoration initiatives. The participation of stakeholders is a vital determinant for increasing public confidence in the government and enhancing the acceptance of government decisions. Conversely, insufficient stakeholder participation in decision-making may lead to resistance to decisions on river restoration projects. Thus, the primary purpose of this investigation is to shed light on the complex interactions between the various drivers that underpin stakeholder participation in the context of the Moat System Restoration Project (MSRP). The extended Theory of Planned Behavior (TPB) describes the relationships between seven drivers that have positively influenced stakeholder participation behaviors: stakeholder attitude, priority, risk perception, trust in government decisions, motivation, intention, and knowledge. The empirical underpinning of this research was obtained through a questionnaire survey conducted in Tianchang, China, encompassing a sample size of 473. The empirical findings discern that stakeholder attitudes vis-à-vis the MSRP favorably influence stakeholder participation behaviors. Additionally, stakeholder motivation and intention have been discerned as catalysts for heightened stakeholder participation behavior. These findings promise to furnish invaluable insights, benefit forthcoming river restoration initiatives, and equip decision-makers with a profound understanding of strategies to enhance stakeholder participation.

Lifestyle and language barriers influence community engagement with green infrastructure

Few studies have focused on value structures, experiences, and cultural diversity as it relates to bioswale planning and implementation. We used 'Point of Opportunity Interactions' to understand previously undocumented views of the Cantonese-speaking immigrant community regarding bioswale design and use for stormwater management in Portland, Oregon, USA. Approximately half of participants were not aware of bioswale function. Maintenance costs and aesthetics were noted concerns, but parking and safety were not. Lack of outreach materials in the Chinese language(s), evening and weekend work schedules, and lack of clarity about maintenance responsibility were among barriers to public participation. Overall, lack of trust for the city and city officials was apparent, and hindered outreach and engagement. Emphasis on informality and place-based data collection near bioswales as neutral outdoors spaces, and proximate to participant residences, facilitated communication with this 'hard-to-reach' population and revealed information that would have gone unknown using traditional outreach strategies.

A place-based risk appraisal model for exploring residents' attitudes toward nature-based solutions to flood risks

Nature-based solutions (NBS) have gained popularity as a sustainable and effective way of dealing with increasing flood risks. One of the key factors that often hinders the successful implementation of NBS is residents' opposition to their implementation. In this study, we argue that the place where a hazard exists should be considered a critical contextual factor alongside flood risk appraisals and perceptions of NBS themselves. We have developed a theoretical framework-the "Place-based Risk Appraisal Model (PRAM)"-that draws on constructs inspired by theories of place and risk perception. A citizen survey (n = 304) was conducted in five municipalities in Saxony-Anhalt, Germany, where dike relocation and floodplain restoration projects have been conducted along the Elbe River. Structural equation modeling was adopted to test the PRAM. Attitudes toward the projects were assessed in terms of "perceived risk-reduction effectiveness" and "supportive attitude." With regard to risk-related constructs, well-communicated information and perceived co-benefits were consistently positive factors for both perceived risk-reduction effectiveness and supportive attitude. Trust in local flood risk management was a positive and threat appraisal a negative predictor of perceived risk-reduction effectiveness affecting "supportive attitude" only through "perceived risk-reduction effectiveness." Regarding place attachment constructs, place identity was a negative predictor of a supportive attitude. The study emphasizes that risk appraisal, pluralities of place contexts to each individual, and their relations are key for determining attitudes toward NBS. Understanding these influencing factors and their interrelationships enables us to provide theory- and evidence-based recommendations for the effective realization of NBS.

Community experiences of landscape-based stormwater management practices: A review

Urban stormwater management increasingly changes urban landscapes. From rain gardens to stormwater ponds, landscape-based practices are visible and often accessible to community members, whose support and experience of these practices will affect their success. This critical narrative review addresses these Landscape-based Stormwater Management Practices (L-SWMPs). It assesses quantitative and qualitative evidence for the effects of characteristics of individual community members, L-SWMP landscape context, and L-SWMPs themselves on community members' perceptions, attitudes, and societal outcomes. Characteristics of community members are most well-studied. Environmental knowledge and past experiences of community members have strong, consistent effects, while the effects of demographic characteristics are weaker and inconsistent. Landscape characteristics, especially greenspace context and neighborhood landscape norms, consistently influence perceptions of L-SWMPs as amenities. Effects of noticeable L-SWMP characteristics are understudied; we argue that paying greater attention to these characteristics may help practitioners innovate L-SWMPs that benefit communities and receive their support.

Spatio-temporal evolution characteristics analysis and optimization prediction of urban green infrastructure: a case study of Beijing, China

The reasonable layout of green infrastructure is conducive to the low-carbon, livable and high-quality sustainable development of cities. The framework of spatio-temporal evolution characteristics and prediction analysis of Urban Green Infrastructure (UGI) was constructed by integrating morphological spatial pattern analysis (MSPA) and CA-Markov in the study. We analyzed the spatio-temporal evolution characteristics of UGI in Beijing from 1990 to 2019, predicted its future change trend in 2030, and put forward the optimization scheme for the ecological network of UGI. The area change of UGI presented a "V" shape from 1990 to 2019 in Beijing, and the turning point was around 2009. Its spatial distribution revealed a significant heterogeneity. The comprehensive change rate index showed a "rising and then falling" trend from 1990 to 2019. Core with an area of over 1000 km² had inclined "C" shape, connecting the north, west and south of the study area. Among the three prediction scenarios for 2030, the area of UGI under the ecological conservation priority scenario is the largest, accounting for 86.35% of the total area. The area of UGI under the economic development priority scenario is the smallest, accounting for 76.85%. The optimization of zoning and road network are effective measures to improve the connectivity of UGI in Beijing. This study is beneficial to extend the research ideas of UGI and promote sustainable urban development.

Assessing the influence of urban greenness and green stormwater infrastructure on hydrology from satellite remote sensing

Green stormwater infrastructure (GSI), which includes features like rain gardens, constructed wetlands, or urban tree canopy, is now widely recognized as a means to reduce urban runoff impacts and meet municipal water quality permit requirements. Many co-benefits of GSI are related to increased vegetative cover, which can be measured with satellite imagery via spectral indices such as the Normalized Difference Vegetation Index (NDVI). In urban landscapes, there remain critical gaps in understanding how urban greenness and GSI influence hydrology. Here, we quantify these relationships to assess the feasibility of tracking the effectiveness of urban greening for improving downstream hydrologic conditions. We combined hydrologic data from the United States Geological Survey (USGS) gauges with an NDVI time series (1985-2019) derived from Landsat satellite imagery, and synthesis of GSI implementation data from a set of 372 urbanized watersheds across the United States. We used a multivariate panel modeling approach to account for spatial and time varying factors (rainfall, temperature, urban cover expansion) in an effort to isolate the relationships of interest. After accounting for expansion of urban boundaries, only 32 watersheds (9%) showed significant greenness trends, a majority of which were reductions. Urban greenness had significant influences on downstream flow responses, so that on average, a 10% greenness increase showed a corresponding reduction of total flow (-3.8%), flow variance (-7.7%), peak flows (-4.7%), high flows (-7.6%), flashiness (-2.2%), and high flow frequency (-1.5%); and a corresponding increase in baseflow (4.3%). For a subset of these watersheds for which GSI data were available (n = 48), the level of GSI implementation showed a significant, but weak influence on urban greenness with a 20% increase in BMP density corresponding to a greenness increase of 0.9%. The study results may support valuation and verification of GSI co-benefits in urbanized landscapes at the watershed scale.

Ecosystem Benefits Provision of Green Stormwater Infrastructure in Chinese Sponge Cities

The Sponge City Development (SCD) concept was initiated in 2012 to address severe urban flooding and water quality challenges in China. Green stormwater infrastructure (GSI) such as rain gardens have been adopted as critical stormwater management tools. Existing GSI research has focused primarily on their environmental performance, overlooking the human dimensions. The co-benefits of GSI have been particularly underinvestigated. We used social surveys (n = 607) and expert interviews (n = 11) to explore public perception of SCD and GSI in four pilot sponge cities, examining flood experience, stormwater concerns, GSI familiarity, institutional trust, and GSI benefit perception. The survey found high exposure to flooding, medium GSI familiarity, and strong institutional trust. The public showed greater concern on stormwater impacts on their quality-of-life than the water environment, rating the less-intended aesthetic and health values as the best-perceived benefits. Experience, familiarity, concern, trust, age, and city significantly affected GSI benefit perception. In contrast, the experts spoke more positively about the environmental benefits while indicating the inadequacy of public participation. The case of GSI in SCD offers broad implications for environmental governance and expert-public relationships in an era of rapid social, technological, and environmental change. Refining policies and regulations to incorporate social goals, bringing the public into the SCD process, and building up the GSI industry's capacity in planning, design, construction, and maintenance are critical to enhancing GSI benefits provision. Adopting the co-benefits approach will be essential to utilizing GSI as a place-making tool to create more sustainable and livable communities.

Public preferences for green infrastructure improvements in Northern New Jersey: a discrete choice experiment approach

Significant water pollution caused by flooding due to heavy precipitation and extreme weather events has become a considerable problem in urbanized areas such as in Northern New Jersey. These cities experience heavy downpour-related contamination and water pollution when stormwater and untreated sewage are diverted through combined sewer overflow drainage systems to adjacent water bodies. Green infrastructure has proven a successful intervention method for mitigating these unintended environmental consequences. However, while the effects of CSOs and the ability of GI to reduce them are well documented, there has been considerably less study addressing public preferences and willingness to pay for GI-based solutions. As such, this study seeks to understand these facets of GI management in urbanized areas of New Jersey, focusing on Newark, Paterson, and Elizabeth townships. A discrete choice experiment method was used to analyze the willingness of residents to pay for additional CSO infrastructure through the installation of GI options such as bioretention gardens, rain barrels, and green roofs. Furthermore, study identified attributes such as secondary benefits, proximity, and water retention that respondents found the most utility in when choosing GI stormwater management interventions. We found that several attributes, including improved air quality ($58.60), increased water supply ($49.71), and closer proximity ($110.01-$125.97) had the highest utility and similarly were associated with a higher willingness to pay than other tested attributes. These findings are important in assessing the overall attitude toward these fixtures, and may be critical in crafting local policy and development, especially to address environmental equity.

Impact of sewer overflow on public health: A comprehensive scientometric analysis and systematic review

Sewer overflow (SO), which has attracted global attention, poses serious threat to public health and ecosystem. SO impacts public health via consumption of contaminated drinking water, aerosolization of pathogens, food-chain transmission, and direct contact with fecally-polluted rivers and beach sediments during recreation. However, no study has attempted to map the linkage between SO and public health including Covid-19 using scientometric analysis and systematic review of literature. Results showed that only few countries were actively involved in SO research in relation to public health. Furthermore, there are renewed calls to scale up environmental surveillance to safeguard public health. To safeguard public health, it is important for public health authorities to optimize water and wastewater treatment plants and improve building ventilation and plumbing systems to minimize pathogen transmission within buildings and transportation systems. In addition, health authorities should formulate appropriate policies that can enhance environmental surveillance and facilitate real-time monitoring of sewer overflow. Increased public awareness on strict personal hygiene and point-of-use-water-treatment such as boiling drinking water will go a long way to safeguard public health. Ecotoxicological studies and health risk assessment of exposure to pathogens via different transmission routes is also required to appropriately inform the use of lockdowns, minimize their socio-economic impact and guide evidence-based welfare/social policy interventions. Soft infrastructures, optimized sewer maintenance and prescreening of sewer overflow are recommended to reduce stormwater burden on wastewater treatment plant, curtail pathogen transmission and marine plastic pollution. Comprehensive, integrated surveillance and global collaborative efforts are important to curtail on-going Covid-19 pandemic and improve resilience against future pandemics.

Resident Knowledge of and Engagement with Green Infrastructure in Toronto and Philadelphia

Green infrastructure (GI) initiatives, including programs to plant trees and install bioswales, have been adopted by a growing number of local government and non-governmental organizations. While the details of these programs vary, a common characteristic of most Canadian and US GI initiatives is a distributed approach that includes both public and private land. To date, little research has explored residents' knowledge of GI or their engagement with related initiatives even though residents' installation of GI is often key to creating distributed GI networks. In this study, we (1) assess residents' knowledge of the term GI, (2) identify residents' level of engagement with GI initiatives, and (3) examine whether factors like level of concern about local environmental issues can predict GI knowledge or level of engagement with GI initiatives. We explored these objectives through a survey of residents in Toronto (Ontario, Canada) and Philadelphia (Pennsylvania, US). We found that about a quarter of survey respondents in both cities had previously heard the term "green infrastructure". Neither knowledge of GI nor level of engagement with GI initiatives could be predicted by the level of concern about local environmental issues, but residents' interest in using their outdoor space for nature activities (e.g., gardening) predicted GI knowledge in both cities and level of initiative engagement in Philadelphia. Our results suggest the need for widespread education campaigns that clearly define GI so that residents can be participants in policy discussions, link it with their needs, and identify ways to manage GI to create desired benefits.

Valuing stakeholder preferences for environmental benefits of stormwater ponds: Evidence from choice experiment

With population growth driving urban expansion in many cities in the United States, there is a need for a sustainable way to manage stormwater. Green stormwater infrastructure (GSI) is considered an innovative way to handle stormwater because of its potential to provide multiple ecosystem services (ES) beyond flooding reduction. However, there is limited research regarding the society's perceived value for GSI practices' co-benefits. This study utilized stated-preference data obtained from a choice experiment in an online survey of 1159 South Carolina (SC) residents to estimate a monetary value for the ES provided by wet detention ponds- the most widely adopted stormwater practice in coastal counties of SC. The benefits examined are flooding reduction, water quality, wildlife habitat, recreation, and scenic beauty. The data were analyzed using a Mixed logit formulation. Considering the differences across the state, the model was estimated separately for five counties. Findings indicate that residents are willing to pay $13.8 to $37.8 annually for a 50% improvement in pollutant removal efficiency of ponds in addition to their current stormwater fee. Also, they are willing to pay $12.5 to $42.9 per year for the nearest pond to have buffer vegetation and wildlife. They are also likely to pay $5 to $22.5 for ponds to contribute to their neighborhood's scenic beauty. Furthermore, the results indicate that respondents from three counties are willing to pay $5.4 to $13.2 for a 50% improvement in flooding reduction, while those from two counties are likely to pay $3.9 to $4.9 for ponds to have recreational benefits. The findings of the study could help stormwater managers in designing their stormwater management programs, especially for better evaluation of stormwater utility fees.

Web of Science-Based Green Infrastructure: A Bibliometric Analysis in CiteSpace

Many cities worldwide are using re-greening strategies to help reverse urbanization patterns that aggravate environmental issues. Green infrastructure (GI) has become a significant and effective strategy to address environmental problems. To better understand GI, this study uses CiteSpace to analyze 5420 published papers in the field of GI on the Web of Science database from 1990-2020. This bibliometric analysis will help new scholars and researchers to better understand the current status and trends in GI research, as well as identify further research needed in the field. This study evaluated research on GI trends according to publication amounts, keywords, journals, disciplines, countries, institutions, and authors. Results show that, first, GI research has experienced rapid growth since 2014. Second, GI, ecosystem services, and city are the top three keywords related to GI research, with green roof as the keyword with the strongest linkage. Third, Sustainability, Urban Forestry and Urban Greening, and Landscape and Urban Planning are the top three journals publishing GI research. Fourth, the top three disciplines researching GI are environmental science, engineering, and science and technology. Fifth, the USA is the top ranked country in terms of the number of published GI-related papers (1514 papers), followed by China (730 papers) and England (546 papers). Sixth, the US Environmental Protection Agency (84 papers) is the top institution in terms of publications, followed by the Chinese Academy of Science (83 papers) and the Swedish University of Agriculture (66 papers). Finally, D. Haase has the most published articles (29 papers), followed by S. Pauleit (28 papers) and P. Angelstam (26 papers). These findings indicate that GI has developed significantly in the last 30 years, with a high probability for increased growth in the future.

Social-psychological Determinants of the Implementation of Green Infrastructure for Residential Stormwater Management

Climate change effects and increasing levels of imperviousness, cause many urban areas globally to experience larger rainfall runoff volumes that need to be managed to protect property and infrastructure, and avoid environmental pollution. Conventionally engineered, 'grey' stormwater infrastructure often is outdated and unable to control these increased runoff volumes. Green stormwater infrastructure (GSI) can complement grey infrastructure, but public land for its installation is limited. Consequently, municipalities often look to residential properties to install GSI at the lot-level. While many studies have been conducted in the engineering aspects of GSI, less is known about what determines residents' decisions to install GSI on their properties. To help close this knowledge gap, we conducted a survey of social-psychological determinants of residential GSI implementation using the Theory of Planned Behavior as theoretical framework, and analyzing our data with partial least squares path modeling. Results from three neighborhoods of our case study area suggest that residents' decisions to install GSI largely are determined by social norms and perceived control factors such as available finances and time. However, residents' beliefs and attitudes toward the effectiveness and attractiveness of GSI did not seem to play a significant role. Neighborhood characteristics including local flooding history did not seem to affect residents' decisions about GSI installation either. We recommend creation of effective municipal education and outreach programs regarding urban stormwater management that speak to residents' shared responsibility and options for addressing this issue, as well as creation of financial instruments that provide meaningful subsidies for residential GSI adoption.

Assessing the Feasibility of a Cloud-Based, Spatially Distributed Modeling Approach for Tracking Green Stormwater Infrastructure Runoff Reductions

Use of green stormwater infrastructure (GSI) to mitigate urban runoff impacts has grown substantially in recent decades, but municipalities often lack an integrated approach to prioritize areas for implementation, demonstrate compelling evidence of catchment-scale improvements, and communicate stormwater program effectiveness. We present a method for quantifying runoff reduction benefits associated with distributed GSI that is designed to align with the spatial scale of information required by urban stormwater implementation. The model was driven by a probabilistic representation of rainfall events to estimate annual runoff and reductions associated with distributed GSI for various design storm levels. Raster-based calculations provide estimates on a 30-m grid, preserving unique combinations of drainage factors that drive runoff production, hydrologic storage, and infiltration benefits of GSI. The model showed strong correspondence with aggregated continuous runoff data from a set of urbanized catchments in Salinas, California, USA, over a three-year monitoring period and output sensitivity to the storm drain network inputs. Because the model runs through a web browser and the parameterization is based on readily available spatial data, it is suitable for nonmodeling experts to rapidly update GSI features, compare alternative implementation scenarios, track progress toward urban runoff reduction goals, and demonstrate regulatory compliance.

Introducing Nature into Cities or Preserving Existing Peri-Urban Ecosystems? Analysis of Preferences in a Rapidly Urbanizing Catchment

Nature-based solutions (NBS) are increasingly being promoted as a means to address societal and environmental challenges, especially flood risk reduction. In the context of rapidly urbanizing catchments, NBS can take part of the development of sustainable cities, either by conserving peri-urban ecosystems from urban sprawl or by developing green infrastructure in the cities. Both can provide a wide range of co-benefits (e.g., climate regulation, air quality regulation), but also generate some negative effects (e.g., mobility issues, unsafety, allergens). We develop and implement a Discrete Choice Experiment survey to analyse people’s perception of co-benefits and negative effects, and associated preferences for the two types of NBS at a catchment scale. The results obtained from 400 households living in a French Mediterranean catchment highlight that people associate numerous co-benefits to NBS, but also negative effects. Our estimations reveal that resident households are ready to contribute large amounts through a tax increase for the development of NBS (from 140 to 180 EUR/year, on average). There is however a strong heterogeneity of preferences at the catchment scale influenced by income, location of the respondent along an urban–rural gradient, and perception of the importance of ecosystem services. These differences may reflect urban environmental inequalities at the catchment scale, which are important to take into account in order to avoid distributive inequalities.

Mitigation of Urban Pluvial Flooding: What Drives Residents’ Willingness to Implement Green or Grey Stormwater Infrastructures on Their Property?

As a consequence of climate change, the impact of pluvial flooding is expected to increase in the next decades. Despite citizens’ poor knowledge, several types of stormwater infrastructure can be implemented to mitigate the impact of future events. This paper focuses on the implementation of green and grey stormwater interventions (i.e., with or without vegetation) on private properties. Framed by the Protection Motivation Theory, a survey-based case study analysis, carried out in a pluvial flooding-prone area of the Veneto Region (Italy), highlights the main factors driving people’s willingness to implement these interventions. The analysis shows that the implementation of grey stormwater infrastructures is driven by the perceived threat and the amount of past pluvial flooding damage (i.e., the direct experience as a proxy of prior knowledge) while the implementation of green stormwater infrastructures is driven also by additional factors (awareness of these interventions, age and education level of the citizens). Based on these results, lack of knowledge on innovative stormwater interventions represents a critical barrier to their implementation on private properties, and it confirms the need for specific dissemination and information activities.

Addressing Challenges of Urban Water Management in Chinese Sponge Cities via Nature-Based Solutions

Urban flooding has become a serious issue in most Chinese cities due to rapid urbanization and extreme weather, as evidenced by severe events in Beijing (2012), Ningbo (2013), Guangzhou (2015), Wuhan (2016), Shenzhen (2019), and Chongqing (2020). The Chinese “Sponge City Program” (SCP), initiated in 2013 and adopted by 30 pilot cities, is developing solutions to manage urban flood risk, purify stormwater, and provide water storage opportunities for future usage. Emerging challenges to the continued implementation of Sponge Cities include (1) uncertainty regarding future hydrological conditions related to climate change projections, which complicates urban planning and designing infrastructure that will be fit for purpose over its intended operating life, and (2) the competing priorities of stakeholders and their reluctance to make trade-offs, which obstruct future investment in the SCP. Nature-Based Solutions (NBS) is an umbrella concept that emerged from Europe, which encourages the holistic idea of considering wider options that combine “Blue–Green” practices with traditional engineering to deliver “integrated systems of Blue–Green–Grey infrastructure”. NBS includes interventions making use of natural processes and ecosystem services for functional purposes, and this could help to improve current pilot SCP practices. This manuscript reviews the development of the SCP, focusing on its construction and design aspects, and discusses how approaches using NBS could be included in the SCP to tackle not only urban water challenges but also a wide range of social and environmental challenges, including human health, pollution (via nutrients, metals, sediments, plastics, etc.), flood risk, and biodiversity.

Attitude and Actual Behaviour towards Water-Related Green Infrastructures and Sustainable Drainage Systems in Four North-Western Mediterranean Regions of Italy and France

Water-related green infrastructures (WrGIs), also known as blue infrastructures, and sustainable drainage systems (SuDSs) offer services such as stormwater runoff management, water purification, water storage at the intersection of the built environment, and natural systems by mimicking natural hydrological processes. While several papers document the reliability of such infrastructures in providing a variety of water-related services, few studies investigated the actual behaviour and the attitude of different stakeholders to understand the limitations and barriers in WrGIs/SuDSs implementation. In this paper, we investigated these issues by posing a set of questions to 71 qualified stakeholders in three Italian regions (Toscana, Liguria, and Sardegna) and one French region (Provence-Alpes-Côte d’Azur) in the northwestern Mediterranean. The results of the investigation largely show a lack of knowledge on these innovative solutions, although there is a general interest in their implementation both in the Italian and French regions. Barriers are also constituted by the scarcity of the demonstrators implemented, little knowledge on construction and maintenance costs, the absence of a proper regulatory framework, and of fiscal and financial incentives to support private citizens and companies. We finally suggest tools and soft measures that, in our opinion, may contribute to supporting the implementation of WrGIs/SuDSs, especially in view of adapting Mediterranean territories to the challenges posed by climate change. The results of our analyses may be reasonably up-scaled to the whole Mediterranean coastal region.

Socio-Economic Assessment of Green Infrastructure for Climate Change Adaptation in the Context of Urban Drainage Planning

Green infrastructure (GI) contributes to improve urban drainage and also has other societal and environmental benefits that grey infrastructure usually does not have. Economic assessment for urban drainage planning and decision making often focuses on flood criteria. This study presents an economic assessment of GI based on a conventional cost-benefit analysis (CBA) that includes several benefits related to urban drainage (floods, combined sewer overflows and waste water treatment), environmental impacts (receiving water bodies) and additional societal and environmental benefits associated with GI (air quality improvements, aesthetic values, etc.). Benefits from flood damage reduction are monetized based on the widely used concept of Expected Annual Damage (EAD) that was calculated using a 1D/2D urban drainage model together with design storms and a damage model based on tailored flood depth–damage curves. Benefits from Combined Sewer Overflows (CSO) damage reduction were monetized using a 1D urban drainage model with continuous rainfall simulations and prices per cubic meter of spilled combined sewage water estimated from literature; other societal benefits were estimated using unit prices also estimated from literature. This economic assessment was applied to two different case studies: the Spanish cities of Barcelona and Badalona. The results are useful for decision making and also underline the relevancy of including not only flood damages in CBA of GI.