Exploring trade-offs among the multiple benefits of green-blue-grey infrastructure for urban flood mitigation

Blue-green infrastructure in view of Integrated Urban Water Management: A novel assessment of an effectiveness index

Addressing urban water management challenges requires a holistic view. Sustainable approaches such as blue-green infrastructure (BGI) provide several benefits, but assessing their effectiveness demands a systemic approach. Challenges are magnified in informal areas, leading to the combination of integrated urban water management (IUWM) with BGI as a proposed solution by this research. We employed the Urban Water Use (UWU) model to assess the effectiveness index (EI) of BGI measures in view of IUWM after stakeholder consultation. The procedure in this novel assessment includes expert meetings for scenario building and resident interviews to capture the community's vision. To assess the impact of IUWM on the effectiveness of BGI measures, we proposed a simulation with BGI only and then three simulations with improvements to the water and sewage systems. The results of the EI analysis reveal a substantial improvement in the effectiveness of BGI measures through IUWM combination. Moreover, we offer insights into developing strategies for UWU model application in informal settlements, transferrable to diverse urban areas. The findings hold relevance for policymakers and urban planners, aiding informed decisions in urban water management.

Coupled and collaborative optimization model of impervious surfaces and drainage systems from the flooding mitigation perspective for urban renewal

Urban pluvial flooding mitigation is a significant challenge in city development. Many mature methods have been used to reduce the risk of flood. The optimal design of impervious surfaces (ODIS) is an adaptive solution to urban flooding from the perspective of urban renewal planning. However, existing ODIS models are limited because they do not consider the drainage systems. To address this issue, this study proposes an elastic and controllable optimization model based on assumptions about rainstorm and drainage capacity, nondominated sorting genetic algorithm-II (NSGA-II), multivariate linear programming (MLP) and soil conservation service curve number model (SCS-CN) in a case study of the old town of Guangzhou city, China. The model not only coupled the drainage systems, but also collaboratively optimized the impervious surfaces and the drainage systems. The results show that the proposed model achieved an optimized efficiency of 5.70 %, which is more than a tenfold improvement compared to existing ODIS models. The study emphasizes that the optimization of the drainage system should be the focus and the optimization of impervious surfaces should be supplementary, and different flood risk areas require different optimization strategies. Furthermore, transforming impervious surfaces into a "high-low-high" spatial distribution of impervious surface densities is the optimal design solution for impervious surfaces. In general, this study offers a novel perspective and approach to urban flooding mitigation, enabling comprehensive control of flooding from a global perspective.

Spatial congruency or discrepancy? Exploring the spatiotemporal dynamics of built-up expansion patterns and flood risk

Most coastal cities have been experiencing unprecedented urbanization-induced flood risk, climatic events, and haphazard anthropogenic activities, jeopardizing residents' lives and building environments. Despite mounting flood-related studies, analyzing the correlation between the spatiotemporal dynamics of Built-up Expansion patterns (BE) and flood risk remains unknown and holds divergent perspectives. In this context, the coastal city of Alexandria, Egypt, characterized by multiple urban patterns and experiencing heavy rainfall annually, was selected as a testbed. Our method defined the spatiotemporal rates of BE from 1995 to 2023, quantified flood risk spatially, and finally investigated the correlation between BE and flood risk through spatial and statistical analysis. Our results show the built-up area occupied 30.32 % of the total city area till 2023, and the infilling pattern dominated the BE growth by 45.21 % of the total built-up area, followed by leapfrogging and edge expansion by 33.25 % and 21.55 %, respectively. The unplanned-infilling pattern is predominantly highly correlated with the flood-vulnerable peaks (correlation coefficient (rk) = 0.975, p-value < 0.05) and lowers dramatically towards planned-infilling regions with flood protections. Meanwhile, a spatial mismatch exists between high-risk peaks and leapfrogging and edge expansion (rk = 0.118 and 0.662, respectively, with a p-value < 0.01), indicating that controlling the built-up amount is inadequate for mitigating flood risk. Porosity-based urban configuration and spatial distribution of built-up patches in harmony with nature-based solutions are recommended for shaping flood-resilient and effective urban planning.

What does it take to renature cities? An expert-based analysis of barriers and strategies for the implementation of nature-based solutions

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.

A drainage network-based impact matrix to support targeted blue-green-grey stormwater management solutions

Urban floods will continue to be an alarming issue worldwide due to climate change and urban expansion. The costly and less environmentally friendly grey infrastructure is not always the most adequate solution to resolve urban pluvial flooding issues. The combination of grey and blue-green infrastructures, also called hybrid infrastructure, has been considered a promising solution for urban stormwater management. Existing approaches for identifying suitable hybrid solutions frequently rely on global multi-objective optimization algorithms. We developed a pre-screening method that decomposes a drainage network into clusters of pipes connected to sub-catchments, based on pipe hydraulic characteristic that allows for the impact of infrastructure combinations (blue-green and grey) to be mapped. Four impact matrices are proposed to map the total, local, upstream, and downstream flood reduction of all possible blue-green, grey, and hybrid solutions. Using an urban catchment in Guangzhou (China) as a case study, results showed that such an exercise could identify prime candidate locations for blue-green and grey infrastructure while filtering out ineffective locations for flood reduction. Furthermore, the impact matrices enabled the identification of flood zones where blue-green infrastructure could handle flood mitigation without the need of local grey infrastructure upgrades. As such, they are not only useful for quick screening of suitable interventions for each flooded zone, but can also potentially serve as a priori knowledge before diving into the data and computationally expensive process of finding the most effective flood mitigation solutions.

Economic assessment of nature-based solutions to reduce flood risk and enhance co-benefits

Flooding is expected to increase due to climate change, urbanisation, and land use change. To address this issue, Nature-Based Solutions (NBSs) are often adopted as innovative and sustainable flood risk management methods. Besides the flood risk reduction benefits, NBSs offer co-benefits for the environment and society. However, these co-benefits are rarely considered in flood risk management due to the inherent complexities of incorporating them into economic assessments. This research addresses this gap by developing a comprehensive methodology that integrates the monetary analysis of co-benefits with flood risk reduction in economic assessments. In doing so, it aspires to provide a more holistic view of the impact of NBS in flood risk management. The assessment employs a framework based on life-cycle cost-benefit analysis, offering a systematic and transparent assessment of both costs and benefits over time supported by key indicators like net present value and benefit cost ratio. The methodology has been applied to the Tamnava basin in Serbia, where significant flooding occurred in 2014 and 2020. The methodology offers valuable insights for practitioners, researchers, and planners seeking to assess the co-benefits of NBS and integrate them into economic assessments. The results show that when considering flood risk reduction alone, all considered measures have higher costs than the benefits derived from avoiding flood damage. However, when incorporating co-benefits, several NBS have a net positive economic impact, including afforestation/reforestation and retention ponds with cost-benefit ratios of 3.5 and 5.6 respectively. This suggests that incorporating co-benefits into economic assessments can significantly increase the overall economic efficiency and viability of NBS.

Identifying changes in flood characteristics and their causes from an event-based perspective in the Central Taihu Basin

Increasing rainstorms induced by climate change and modification in the land surface due to urbanization have greatly altered floods at different spatio-temporal scales. However, investigating flood events in urbanized plains is challenging as anthropogenic behaviors can change river flow without rainfall. In addition, while the frequency and magnitude of floods have been well examined, knowledge about variations in the rate of flood change is still limited. To fill these gaps, we proposed a scheme that focused on flood responses to rainfall to detect changes in flood characteristics in the Central Taihu Basin, a highly urbanized region in the Yangtze River Delta of China. Four characteristic metrics were adopted to summarize the flood hydrograph, including the peak, increment, rising rate, and falling rate. We then examined trends of these metrics based on the selected rainfall-flood events from ten hydrological stations during 1970-2020. Subsequently, the reduction method was used to separate the impacts of regional climate change and human activities on flood characteristics alterations. Furthermore, the importance of fifteen factors was quantified by the random forest model. We found that there is a significant upward trend in the evolution of flood characteristics, except for the increment of floods. Flood characteristics exhibit higher values when rainfall accumulates, indicating stronger responses of floods to a large amount of rainfall. The results also show that human activities dominate and impact the peak, rising rate, and falling rate of floods more than climate change. Meanwhile, although cumulative precipitation is the most important factor, flood characteristics are also susceptible to anthropogenic factors, such as land use change and hydraulic engineering construction. Our findings, which provide insights into flood event identification and enhance the understanding of regional flood changes, will serve as a reference for water resource management and flood mitigation in urbanized areas.

Pluvial flood adaptation using nature-based solutions: An integrated biophysical-economic assessment

Globally, flood events are considered the costliest natural hazard. Changes in precipitation patterns and large areas of impervious surfaces in urban environments are increasing the sensitivity of these systems to runoff production. At the same time, projected global sea-level rise may further increase the frequency of compound flooding due to simultaneous storm surge, sea-level rise and pluvial runoff that cause vast socio-economic and ecological impacts to coastal cities. In this context, over the last decade, the role of Nature-Based Solutions (NBS) has been recognised to support climate change adaptation by addressing ideas of multi-functionality, non-linearity and heterogeneity in urban design. Thus, increasing awareness about NBS benefits increases the willingness to accept these solutions. However, empirical evidence of NBS effectiveness at the urban catchment scale is still subject to debate. This study develops a spatial biophysical-economic framework that allows for the integrated assessment of NBS flood risk mitigation impacts, costs and benefits in the face of climate change, combining the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model, benefit transfer methods and Geographic Information System (GIS) tools. Specifically, the InVEST Urban Flood Risk Mitigation model was used to assess the biophysical impacts of NBS on urban pluvial flood risk, benefit-transfer methods were used to evaluate the economic implications of such solutions, and GIS was used to integrate and map biophysical impacts and economic implications. For the case of the coastal lagoon city of Aveiro (Portugal), NBS scenarios of green roofs and bioswales under current and future climate conditions were assessed. The main findings of this study show that green roofs scenarios would save 32 % of the flood damages to buildings and infrastructures every year, while bioswales help save only 0.1 %. Moreover, green roofs implementation provides larger benefits in the future climate scenario (representative concentration pathway - RCP - 4.5). The findings confirm the extent to which knowledge on NBS benefits and costs is partial and uncertain, thus requiring constant progress through biophysical-economic assessment to support an evolutive decision making process in climate adaptation planning.

Non-structural flood mitigation optimization at community scale: Middle Cedar Case Study

Flooding is the leading natural hazard in Iowa and has resulted in billions of dollars of damage to properties and critical infrastructure over the past couple of decades. Land alterations, urbanization, and changing precipitation regimes increase the magnitude and frequency of flood events. Considering the increasing risk, flood mitigation efforts are significant to reduce future losses. In this study, we present a comprehensive flood mitigation assessment for the cities of Cedar Falls, Cedar Rapids, and Waterloo in Iowa, utilizing various datasets such as property information, flood inundation maps, mitigation costs, and depth-damage functions. The research revealed that flooding has a minimal impact on Waterloo below the 200-year return period flood scenario, but Cedar Falls and Cedar Rapids are significantly vulnerable, requiring more mitigation investments and planning. The study conducted a benefit-cost analysis, indicating that dry floodproofing is the most feasible option to reduce flood impacts in all studied communities. Moreover, the research conducted a climate data-driven analysis, which found that elevating structures significantly increases the number of feasible mitigation options, regardless of various long-term climate projections. The study also analyzed predetermined mitigation budgets, revealing potential avoided losses and benefit-cost ratios for properties with the highest BCRs and prioritizing them to maximize the total benefit to the communities. The study findings offer crucial insights and recommendations to guide decision-makers in the community on prioritizing cost-effective flood mitigation strategies and minimizing flood impact in the studied regions.

Assessing the effectiveness of nature-based solutions-strengthened urban planning mechanisms in forming flood-resilient cities

Cities have experienced rapid urbanization-induced harsh climatic events, especially flooding, inevitably resulting in negative and irreversible consequences for urban resilience and endangering residents' lives. Numerous studies have analyzed the effects of anthropogenic practices (land use changes and urbanization) on flood forecasting. However, non-structural mitigation's effectiveness, like Nature-Based Solutions (NBS), has yet to receive adequate attention, particularly in the Middle East and North Africa (MENA) region, which have become increasingly significant and indispensable for operationalizing cities efficiently. Therefore, our study investigated the predictive influence of incorporating one of the most common NBS strategies called low-impact development tools (LID) (such as rain gardens, bio-retention cells, green roofs, infiltration trenches, permeable pavement, and vegetative swale) during the urban planning of Alexandria, Egypt, which experiences the harshest rainfall annually and includes various urban patterns. City characteristics-dependent 14 LID scenarios were simulated with recurrence intervals ranging from 2 to 100 years using the LID Treatment Train Tool (LID TTT), depending on calibrated data from 2015 to 2020, by the Nash-Sutcliffe efficiency index and deterministic coefficient, and root-mean-square error with values of 0.97, 0.91, and 0.31, respectively. Our findings confirmed the significant effectiveness of combined LID tools on total flood runoff volume reduction by 73.7%, revealing that different urban patterns can be used in flood-prone cities, provided LID tools are considered in city planning besides grey infrastructure to achieve optimal mitigation. These results, which combined multiple disciplines and were not explicitly mentioned in similar studies in developing countries, may assist municipalities' policymakers in planning flood-resistant, sustainable cities.

Real time control of nature-based solutions: Towards Smart Solutions and Digital Twins in Rangsit Area, Thailand

The intensity and frequency of hydro-meteorological hazards have increased due to fast-growing urbanisation activities and climate change. Hybrid approaches that combine grey infrastructure and Nature-Based Solutions (NBSs) have been applied as an adaptive and resilient strategy to cope with climate change uncertainties and incorporate other co-benefits. This research aims to investigate the feasibility of Real Time Control (RTC) for NBS operation in order to reduce flooding and improve their effectiveness. The study area is the irrigation and drainage system of the Rangsit Area in Thailand. The results show that during the normal flood events, the RTC system effectively reduces water level at the Western Raphiphat Canal Station compared to the system without RTC or with additional storage. Moreover, the RTC system facilitates achieving the required minimum volume and increasing the volume in the retentions. These findings highlight the potential of using RTC to improve the irrigation and drainage system operation as well as NBS implementation to reduce flooding. The RTC system can also assists in equitable water distribution between Klongs and retention areas, while also increasing the water storage in the retention areas. This additional water storage can be utilized for agricultural purposes, providing further benefits. These results represent an essential starting point for the development of Smart Solutions and Digital Twins in utilizing Real-Time Control for flood reduction and water allocation in the Rangsit Area in Thailand.

Interactions of hydrology, geochemistry, and biodiversity in woodland ponds located in riverine floodplains: case study from Scotland

The Gore Glen pond is located in the forested floodplain of the Gore River, in the Mid-Lothian region near Edinburgh, Scotland. This work has considered in detail the hydrology, hydrochemistry, and biodiversity of the pond together with all their interactions and in addition interactions with the adjacent Gore River. It is important as it is one of few studies considering all these issues for a pond located in a riverine floodplain. This work shows the pond is connected to the Gore River for discharge events in the river larger than a 1 in 5-year return period. For these events, the pond acts as an online storage feature and will attenuate the flow, thus contributing towards the mitigation of downstream flooding. These large events are also a potential source of the large amount of sediments, as well as adsorbed chemicals, accumulated in the pond. The open water surface of the pond is covered by duckweed, Lemna minor, for most of the year, and that has profound implications for the hydrobiological community and biogeochemical cycling. The system is characterised by nutrient release from sediments due to the extensive hypolimnion anoxia in the summer/autumn period caused by the decomposition of organic matter. Algae are mostly represented by epiphytic diatoms and the cyanobacterium Microcystis, but their development appears to be constrained by light penetration. The eutrophic conditions are also conducive for the population of Difflugia (Protozoa, Rhizopoda). This work improves our understanding of the ecological relations of testate amoebae-an important group which has recently been used as biological indicators for the analysis of paleoecological relationships and paleogeographical reconstructions.

A critical review of Natural Flood Management application and spatial prioritisation approaches in tropical island catchments

Tropical island communities face substantial hydrometrological threats, including flood inundation. Flood risk is increasing, driven by climate change but also other factors including urbanisation, land-cover and land-use (LCLU) change, making flood management challenging to address in practice. Protecting, restoring, and emulating the natural functions of catchments to reduce flood risk, also known as Natural Flood Management (NFM), is a promising method for improving flood management. Global NFM research is in its infancy and NFM research in tropical island states has tended to focus on individual catchment projects. Therefore, overall trends, challenges, and opportunities for NFM in tropical island catchments are poorly understood and, until now, have not been reviewed across these geographies. A particular gap in NFM understanding in tropical island catchments is how NFM options can be best implemented within any particular catchment - specifically where NFM should be located, how modelling can support these decisions and the influence of different catchment characteristics on these decisions. This literature review aims to explore what, where and how NFM has been used in catchments in tropical island states, with a specific focus on catchment characteristics and spatial modelling. This paper draws on research and interconnections between multiple environmental science spheres, by reviewing both academic and grey literature to better understand how NFM has been applied in tropical island states, with a primary focus on Pacific Island Countries and Territories (PICTs). The research highlights that some islands have greater potential for exploiting NFM due to their physical catchment characteristics and data availability. NFM spatial modelling approaches need to be further developed and adapted to specific tropical island community requirements to improve inland flood resilience at the pace needed and to ensure resources are directed optimally.

Multi-objective optimization methodology for green-gray coupled runoff control infrastructure adapting spatial heterogeneity of natural endowment and urban development

Cost-effective runoff control scheme drafting involves localization, multi-sector coordination, and configuration of multifunctional infrastructures. Numerous independent variables, parameters, weights, and objectives make runoff control optimization quantitatively arduous. This study innovatively proposed a multi-objective optimization methodology for green-gray coupled runoff control infrastructure adapting spatial heterogeneity of natural endowment and urban development. The quantitative methods of multi-objective evaluation, hydrological feature partition, and pressure-adapted multi-objective weight assignment were proposed. Remote sensing inversion of water quality, hydrological model simulation (using SWAT and SWMM software), landscape pattern index calculation, life cycle cost (LCC), life cycle assessment (LCA) on ecological impact, and NSGA-II optimization algorithm were applied. Wuhan, the most water-sensitive city in China, was studied as a case. Runoff control function (RCF), capital investment (CI), and ecological return on investment (EROI) served as optimized objectives. High, medium, and low built-up regions in Wuhan urban development planning district were extracted by topographic factors and landscape patterns, which comprised 28, 34, and 38% of the case area, respectively. Three corresponding hydrological models were then built to illustrate distinct runoff control cost-efficiency in each region. Pressure distributions on runoff control, economic constraints, and ecological resource scarcity were quantitatively evaluated. And four pressure zones were clustered, which occupied 36, 29, 16, and 19% of the case area, respectively. Then the zonal weighted optimization decision-making matrix (with 3 hydrological models and 5 wt) was established by overlaying the pressure zone and built-up zone. In high, medium, and low built-up regions, optimized solutions reduced annual runoff volume by 86, 82%, and 77%The average runoff investments per square meter of impervious underlying surface in high, medium, and low built-up regions were 34.2, 18.7, and 7.9 RMB yuan, respectively. Medium and low built-up regions may only need 55 and 23% of the high built-up region for the unitary impervious underlying surface to balance runoff control and ecological benefits. Runoff control and financial utilization efficiency enhance with hydrological differentiation zones. Thus, the optimization solutions are zonal adaptive, refined, comparable, replicable, and implementable.

Multi-stage planning of LID-GREI urban drainage systems in response to land-use changes

Long-term planning of urban drainage systems aimed at maintaining the sustainability of urban hydrology remains challenging. In this study, an innovative multi-stage planning framework involving two adaptation pathways for optimizing hybrid low impact development and grey infrastructure (LID-GREI) layouts in opposing chronological orders was explored. The Forward Planning and Backward Planning are adaptation pathways to increase LID in chronological order based on the initial development stage of an urban built-up area and reduce LID in reverse chronological order based on the final development stage, respectively. Two resilience indicators, which considered potential risk scenarios of extreme storms and pipeline failures, were used to evaluate the performance of optimized layouts when land-use changed and evolved over time. Compared these two pathways, Forward Planning made the optimized layouts more economical and resilient in most risk scenarios when land-use changed, while the layouts optimized by Backward Planning showed higher resilience only in the initial stage. Furthermore, a decentralized scheme in Forward Planning was chosen as the optimal solution when taking costs, reliability, resilience, and land-use changes into an overall consideration. Nevertheless, this kind of reverse optimization order offers a novel exploration in planning pathways for discovering the alternative optimization schemes. More comprehensive solutions can be provided to decision-makers. The findings will shed a light on the exploration of optimized layouts in terms of spatial configuration and resilience performance in response to land-use changes. This framework can be used to support long-term investment and planning in urban drainage systems for sustainable stormwater management.

Optimization of in-pipe storage capacity use in urban drainage systems with improved DP considering the time lag of flow routing

The active control of urban drainage systems (UDSs) is playing an increasingly important role in the world threatened by urban flooding and associated disasters caused by insufficient drainage capacity. However, little research has recognized the importance of the optimal use of in-pipe storage space. To address this issue, the use of the in-pipe storage capacity was optimized in this study. A novel approach, that is, dynamic programming with successive approximation considering the time lag of flow routing (DPSA-TL), was developed to determine the control policies, in addition to the commonly used passive, rule-based control (RBC), and evolutionary algorithm (EA) strategies. A real-life urban catchment considering flooding control and combined sewer overflow (CSO) reduction was used as the case study. First of all, the potential benefit of maximizing the use of in-pipe storage space was tested using the four control strategies in three storm events, including a 3-year, 2-hour design (46.5 mm), a 5-year, 2-hour design (56.0 mm) and a 7-h historical (152.5 mm) storm events. Results indicate that DPSA-TL performed best in all cases. Without compromising the goal of flooding control, it provided 16.5%, 12.6%, and 3.0% reductions in CSO volume for the three storm events when compared with the passive strategy. Due to the limited capacity of in-pipe storage, the relative improvement diminished as the total rainfall depth increased. Then, control strategies were further applicated to the real-time operation. DPSA-TL was found to be the best alternative for CSO control, with the CSO volume reduced by 14.7%, 11.4%, and 2.5% in the three storm events, respectively. The findings suggest that the performance of UDS can be significantly improved by optimizing the use of in-pipe storage capacity, and the proposed method is effective in the offline optimization and real-time control of UDSs.

Knowledge gaps and future research needs for assessing the non-market benefits of Nature-Based Solutions and Nature-Based Solution-like strategies

Nature-Based Solutions (NBS) can be defined as solutions based on natural processes that meet societal challenges and simultaneously provide human well-being and biodiversity benefits. These solutions are envisioned to contribute to operationalizing sustainable development strategies, especially in the context of adaptation to climate change (e.g. flood risk reduction). In order to quantify NBS performance, ease their uptake and advocate for them as alternatives to "business-as-usual" infrastructures, a comprehensive, holistic valuation of their multiple benefits (multiple advantages and disadvantages) is needed. This entails quantifying non-market benefits for people and nature in addition to determining the (direct) cost-benefit of the risk-reduction measure. Despite the importance given to the assessment of non-tangible benefits for people and nature in the literature, systematic data collection on these dimensions seems to be missing. This study reviews publications that used stated preference methods to assess non-market human benefits of NBS and NBS-like strategies. Its aim is to highlight any biases or knowledge gaps in this kind of evaluation. Our results show that the valuation of non-tangible benefits of NBS (e.g. increased recreation and well-being, enhanced biodiversity) still suffers from a lack of common framing. Despite some steps being taken on enabling interconnected benefit assessments, unexploited opportunities concerning the integrated assessment of non-market human and nature benefits predominate. Moreover, the research to-date appears based on a case-to-case approach, and thus a shared holistic method does not emerge from the present literature, potentially delaying the uptake of NBS. We argue that future research could minimize missed opportunities by focusing on and systematically applying holistic benefits assessments. Methods based on stated preference surveys may help to ensure holistic approaches are taken, as well as contributing to their replicability and application when upscaling NBS.

Identifying barriers for nature-based solutions in flood risk management: An interdisciplinary overview using expert community approach

The major event that hit Europe in summer 2021 reminds society that floods are recurrent and among the costliest and deadliest natural hazards. The long-term flood risk management (FRM) efforts preferring sole technical measures to prevent and mitigate floods have shown to be not sufficiently effective and sensitive to the environment. Nature-Based Solutions (NBS) mark a recent paradigm shift of FRM towards solutions that use nature-derived features, processes and management options to improve water retention and mitigate floods. Yet, the empirical evidence on the effects of NBS across various settings remains fragmented and their implementation faces a series of institutional barriers. In this paper, we adopt a community expert perspective drawing upon LAND4FLOOD Natural flood retention on private land network (https://www.land4flood.eu) in order to identify a set of barriers and their cascading and compound interactions relevant to individual NBS. The experts identified a comprehensive set of 17 barriers affecting the implementation of 12 groups of NBS in both urban and rural settings in five European regional environmental domains (i.e., Boreal, Atlantic, Continental, Alpine-Carpathian, and Mediterranean). Based on the results, we define avenues for further research, connecting hydrology and soil science, on the one hand, and land use planning, social geography and economics, on the other. Our suggestions ultimately call for a transdisciplinary turn in the research of NBS in FRM.

A review of serious games for urban water management decisions: current gaps and future research directions

Urban water management (UWM) is a complex problem characterized by multiple alternatives, conflicting objectives, and multiple uncertainties about key drivers like climate change, population growth, and increasing urbanization. Serious games are becoming a popular means to support decision-makers who are responsible for the planning and management of urban water systems. This is evident in the increasing number of articles about serious games in recent years. However, the effectiveness of these games in improving decision-making and the quality of their design and evaluation approaches remains unclear. To understand this better, in this paper, we identified 41 serious games covering the urban water cycle. Of these games, 15 were shortlisted for a detailed review. By using common rational decision-making and game design phases from literature, we evaluated and mapped how the shortlisted games contribute to these phases. Our research shows that current serious game applications have multiple limitations: lack of focus on executing the initial phases of decision-making, limited use of storytelling and adaptive game elements, use of low-quality evaluation design and explicit indicators to measure game outcomes, and lastly, lack of attention to cognitive processes of players playing the game. Addressing these limitations is critical for advancing purposeful game design supporting UWM.

A SUDS Planning Decision Support Tool to Maximize Ecosystem Services

In the past years, alternative drainage approaches have emerged, such as Sustainable Urban Drainage Systems (SUDS), to prevent run-off and flooding impacts on the most vulnerable zones of the cities. These systems not only provide the benefit of water regulation but also promote other types of ecosystem services. Several studies have developed optimization tools to assist SUDS selection, location, and design. However, they do not consider a comprehensive set of ecosystem services (e.g., provision, regulation, cultural, and support services). This research proposes a flexible and adaptable methodology to incorporate SUDS in different stages of urban projects using a multi-objective optimization technique to minimize run-off, maximize ecosystem services and minimize cost. The methodology comprises four phases: (1) the preliminary analysis of ecosystem services potentially generated by each SUDS type, (2) the priority and opportunity index quantification, (3) the physical feasibility analysis, and (4) the multi-objective optimization tool implementation. The methodology was successfully applied to three different urban areas of Bogotá city (Colombia). Results evidence that the interaction of the budget constraints and the available area restrict the potential benefits of SUDS implementation. These results are helpful to support different urban planning stages.

A Stochastic Conflict Resolution Optimization Model for Flood Management in Detention Basins: Application of Fuzzy Graph Model

Floods are a natural disaster of significant concern because of their considerable damages to people’s livelihood. To this extent, there is a critical need to enhance flood management techniques by establishing proper infrastructure, such as detention basins. Although intelligent models may be adopted for flood management by detention basins, there is a literature gap on the optimum design of such structures while facing flood risks. The presented study filled this research gap by introducing a methodology to obtain the optimum design of detention basins using a stochastic conflict resolution optimization model considering inflow hydrographs uncertainties. This optimization model was developed by minimizing the conditional value-at-risk (CvaR) of flood overtopping, downstream flood damage, and deficit risk of water demand, as well as the deviation of flood overtopping and downstream damage based on non-linear interval number programming (NINP), for four different outlets types via a robust optimization tool, namely the non-dominated sorting genetic algorithm-III (NSGA-III). Conflict resolution was performed using the graph model for conflict resolution (GMCR) technique, enhanced by fuzzy preferences, to comply with the authorities’ priorities. Results indicated that the proposed framework could effectively design optimum detention basins consistent with the regional and hydrological standards.

Towards the long term implementation of real time control of combined sewer systems: a review of performance and influencing factors

Real Time Control (RTC) is widely accepted as a cost-effective way to operate urban drainage systems (UDS) effectively. However, what factors influence RTC efficacy and how this might change in the long term remains largely unknown. This paper reviews the literature to understand what these factors likely are, and how they can be assessed in the future. Despite decades of research, inconsistent definitions of the performance of RTC are used, hindering an objective and quantitative examination of the benefits and drawbacks of different control strategies with regard to their performance and robustness. Furthermore, a discussion on the changes occurring and projected to occur to UDS reveals that the potential impact of these changes on the functioning of RTC systems can be significant and should be considered in the design stage of the RTC strategy. Understanding this 'best-before' characteristic of an RTC strategy is the key step to ensure long term optimal functioning of the UDS. Additionally, unexplored potential for RTC systems might exist in the transitions, rehabilitation and construction of drainage systems. The research gaps highlighted here could guide the way for further development of RTC strategies, and enabling more optimal, long term implementation of RTC for urban drainage systems.

Sustainable Urban Drainage System (SUDS) modeling supporting decision-making: A systematic quantitative review

Decision Support Systems (DSS) for Sustainable Urban Drainage Systems (SUDS) are a valuable aid for SUDS widespread adoption. These tools systematize the decision-making criteria and eliminate the bias inherent to expert judgment, abridging the technical aspect of SUDS for non-technical users and decision-makers. Through the collection and careful assessment of 120 papers on SUDS models and SUDS-DSS, this review shows how these tools are built, selected, and used to assist decision-makers questions. The manuscript classifies the DSS based on the question they assist in answering, the spatial scale used, the software selected, among other aspects. SUDS-DSS aspects that require more attention are identified, including environmental and social considerations, SUDS trains performance and criteria for selection, stochasticity of rainfall, and future scenarios impact. Suggestions for SUDS-DSS are finally offered to better equip decision-makers in facing emerging stormwater challenges in urban centers.

Developing an Approach for Assessing Urban Blue-Green Spaces Towards Sustainable Urban Growth Through Retrospective Cyber Metrics Analysis of Operational Estimations Approaches

Urban blue-green spaces provide us abundant social, environmental, and economic benefits, but the disparities often exist in their distribution and accessibility. Traditionally urban blue-green spaces are a consolidation of “blue-green infrastructure” within urban areas. Several urban features like parks, forests, gardens, visible water, such as parks, rivers, canals, reservoirs, ponds, lakes, fountains, etc. are categorized or considered under the blue-green spaces and these are very much crucial for various urban ecosystem services. These play a significant role for all stakeholders of the urban community. Thus, everyone must ensure the equitable number of blue-green spaces for all. Recently, several rules and regulations towards the safeguarding of urban blue-green spaces have been outlined. The work presents a methodological framework to develop an approach towards sustainable urban growth with the help of urban blue-green spaces assessments. The current work has attempted to examine the linkage between issues of the urban blue-green spaces for restoring the required infrastructures. It can be utilised for all sustainable urban development for urban planning and design projects to play a pivotal role. The work emphasizes more to develop a methodological framework to analyze the urban blue-green spaces for augmentation with a theoretical framework. It is expected that the advancement of a problem cum objectives-driven approach will help to design an impact-driven approach for planned and concrete action.

Integrating ecosystem services into sustainable landscape management: A collaborative approach

The Paiva River is considered one of the least polluted rivers in Europe and its watershed has a high conservation value. However, the Paiva River basin suffers pressures related with recurrent disturbances in land use, such as forest fires, agricultural activities, urbanization and pressures that affect the natural hydromorphological conditions and the continuity of watercourses. Blue and Green Infrastructures (BGINs) emerge to improve biodiversity, sustainability and the supply of ecosystem services while improving socioeconomic aspects. Thus, this article aims to identify priority areas in the basin, for intervention with these infrastructures. For that, a spatial multicriteria decision analysis (MDCA) was carried out according to several data related to the Paiva River Basin. As local politicians and responsible entities for the natural resources management are the main experts on the problems and their possible solutions at the local level, they were involved in this decision-making model. Therefore, these specialized stakeholders did the weighting assignment according to the most or least importance of the same for the work. The map of priority locations to implement BGINs was obtained in the sequel. To the top 5 priority areas, stakeholders attributed the best solutions based on nature. The most recommended BGINs were recovery/maintenance of riparian vegetation and conservation and reforestation of the native forest, both presented in four of the five areas, and introduction of fuel management strips presented in three of the five areas. Thus, we concluded that it is extremely important to include the communities and the competent entities of nature and environment management in scientific projects related to conservation, forming a synergy that makes it possible to combine scientific knowledge with local experience acquired in the field. This project uses a very flexible methodology of local data and can be a great example to be implemented in other hydrographic basins anywhere in the world.

Effectiveness of small- and large-scale Nature-Based Solutions for flood mitigation: The case of Ayutthaya, Thailand

There is growing evidence that traditional response to floods and flood-related disaster is no longer achieving desirable results. Nature-Based Solutions (NBS) represent a relatively new response towards disaster risk reduction, water security, and resilience to climate change, which has a potential to be more effective and sustainable than traditional measures. However, in practice, these measures are still being applied at a slow rate while traditional grey infrastructure remains as a preferred choice. This can be attributed to several barriers which range from political and governance to social and technological/technical. More generally, there is a lack of sufficient knowledge base to accelerate their wider acceptance and uptake. The present work provides contribution in this direction and addresses the question of effectiveness of different types of NBS (i.e., small- and large-scale NBS) and their hybrid combinations with grey infrastructure. The work has been applied on the case of Ayutthaya, Thailand. The results suggest that the effectiveness of small-scale NBS is limited to smaller rainfall events whereas the larger (or extreme) events necessitate combinations of different kinds of measures with different scales of implementation (i.e., hybrid measures).

Exploring Options for Flood Risk Management with Special Focus on Retention Reservoirs

Floods are among the most frequent and deadliest natural disasters, and the magnitude and frequency of floods is expected to increase. Therefore, the effects of different flood risk management options need to be evaluated. In this study, afforestation, permeable concrete implementation, and the use of dry and wet retention reservoirs were tested as possible options for urban flood risk reduction in a case study involving the Glinščica river catchment (Slovenia). Additionally, the effect of dry and wet reservoirs was investigated at a larger (catchment) scale. Results showed that in the case of afforestation and permeable concrete, large areas are required to achieve notable peak discharge reduction (from a catchment scale point of view). The costs related to the implementation of such measures could be relatively high, and may become even higher than the potential benefits related to the multifunctionality and multi-purpose opportunities of such measures. On the other hand, dry and wet retention reservoirs could provide more significant peak discharge reductions; if appropriate locations are available, such reservoirs could be implemented at acceptable costs for decision makers. However, the results of this study show that reservoir effects quickly reduce with scale. This means that while these measures can have significant local effects, they may have only a minor impact at larger scales. We found that this was also the case for the afforestation and permeable concrete.

Nature-based solutions efficiency evaluation against natural hazards: Modelling methods, advantages and limitations

Nature-based solutions (NBS) for hydro-meteorological risks (HMRs) reduction and management are becoming increasingly popular, but challenges such as the lack of well-recognised standard methodologies to evaluate their performance and upscale their implementation remain. We systematically evaluate the current state-of-the art on the models and tools that are utilised for the optimum allocation, design and efficiency evaluation of NBS for five HMRs (flooding, droughts, heatwaves, landslides, and storm surges and coastal erosion). We found that methods to assess the complex issue of NBS efficiency and cost-benefits analysis are still in the development stage and they have only been implemented through the methodologies developed for other purposes such as fluid dynamics models in micro and catchment scale contexts. Of the reviewed numerical models and tools MIKE-SHE, SWMM (for floods), ParFlow-TREES, ACRU, SIMGRO (for droughts), WRF, ENVI-met (for heatwaves), FUNWAVE-TVD, BROOK90 (for landslides), TELEMAC and ADCIRC (for storm surges) are more flexible to evaluate the performance and effectiveness of specific NBS such as wetlands, ponds, trees, parks, grass, green roof/walls, tree roots, vegetations, coral reefs, mangroves, sea grasses, oyster reefs, sea salt marshes, sandy beaches and dunes. We conclude that the models and tools that are capable of assessing the multiple benefits, particularly the performance and cost-effectiveness of NBS for HMR reduction and management are not readily available. Thus, our synthesis of modelling methods can facilitate their selection that can maximise opportunities and refute the current political hesitation of NBS deployment compared with grey solutions for HMR management but also for the provision of a wide range of social and economic co-benefits. However, there is still a need for bespoke modelling tools that can holistically assess the various components of NBS from an HMR reduction and management perspective. Such tools can facilitate impact assessment modelling under different NBS scenarios to build a solid evidence base for upscaling and replicating the implementation of NBS.

Ecosystem Services and Disservices of Vegetation in Recreational Urban Blue-Green Spaces—Some Recommendations for Greenery Shaping

Urban water bodies are an important asset in terms of climate change. The accompanying vegetation is an integral part of the waterside space system and a source of ecosystem services and disservices. The composition of greenery in waterside spaces should therefore be preceded by detailed research. This research would be the basis for the development of recommendations for enhancement of the positive impact of vegetation on humans and minimisation of its negative effect. The aim of the study was to identify ecosystem services and disservices of vegetation in the four most important waterside recreation spaces in the city of Rzeszów, Poland, and to develop plant composition guidelines. A detailed inventory of vegetation and aerobiological monitoring of the presence of airborne allergenic pollen grains and fungal spores were carried out. Next, the ecosystem services and disservices of the vegetation were determined based on literature data and on our expert judgement. Additionally, a counting of the number of visitors to waterside areas was conducted. All these steps were used to develop recommendations for shaping the vegetation of study areas. The results of the investigations show that the boulevards along the artificial lake function completely differently than other investigated places as the area resembles an urban park, and the water is not the main attraction in this space. The vegetation of the boulevards and the nearby gravel-pit bathing area has mostly a spontaneous character and offers the widest range of ecosystem services and disservices. The management of the vegetation should focus on its health-enhancing values. The vegetation growing near the outdoor swimming pools has been designed by man. Nevertheless, it requires recomposing and is targeted specifically at the enhancement of the visual attractiveness. Additionally, there is a need for planting compact deciduous trees that will provide shade at the multi-media fountain.

Multi-Objective Model-Based Assessment of Green-Grey Infrastructures for Urban Flood Mitigation

This paper presents the performance quantification of different green-grey infrastructures, including rainfall-runoff and infiltration processes, on the overland flow and its connection with a sewer system. The present study suggests three main components to form the structure of the proposed model-based assessment. The first two components provide the optimal number of green infrastructure (GI) practices allocated in an urban catchment and optimal grey infrastructures, such as pipe and storage tank sizing. The third component evaluates selected combined green-grey infrastructures based on rainfall-runoff and infiltration computation in a 2D model domain. This framework was applied in an urban catchment in Dhaka City (Bangladesh) where different green-grey infrastructures were evaluated in relation to flood damage and investment costs. These practices implemented separately have an impact on the reduction of damage and investment costs. However, their combination has been shown to be the best action to follow. Finally, it was proved that including rainfall-runoff and infiltration processes, along with the representation of GI within a 2D model domain, enhances the analysis of the optimal combination of infrastructures, which in turn allows the drainage system to be assessed holistically.

A land-use decision approach integrating thermal regulation, stormwater management, and economic benefits based on urbanization stage identification

Driven by global climate change and urbanization, urban heat island (UHI) and urban storm flood (USF) have become the most frequent and influential hazards in recent decades. Land-use optimization can effectively cope with these hazards. However, the trade-offs between multi-hazard mitigation and economic development impose many limitations in practice. Furthermore, current region-based optimization methods no longer meet the precise management demand, and both subdivision and spatial heterogeneity identification have the potential for wider applicability. Hence, a systematic integration of climate adaptation and urban construction through land-use planning is urgently required. This paper proposes a new land-use decision approach for improving climate adaptability of urbanization. This approach involves multi-objective optimization, spatial subdivision, and urbanization stage identification, which enable the simultaneous achievement of environmental and economic benefits. Taking Xiamen as case study, the results showed that excessive pursuit of land economic output (LEO) limits the chance of mitigating UHI and USF. Improving the LEO per unit area of construction land could disrupt the link between land exploitation and the increasing side effects of climate hazards. Future urbanization hotspots in Xiamen will likely emerge at the urban fringe in Tong'an District and Xiang'an District. Within each developing unit, the upper limit of construction land was 81.06 hm² and the green space was recommended to be 7.29-21.94 hm². Construction land and bare land contributed most to UHI and USF, while forest and grassland were highly efficient in heat and runoff mitigation. The developed approach proved to be effective and practicable, especially for reducing the impacts of extreme UHI and USF.

Nature-Based Solutions Tools for Planning Urban Climate Adaptation: State of the Art

Despite the recognized potential of nature-based solutions (NBSs) to support climate adaptation, there are still wide barriers for a wider uptake of such NBS in urban areas. While tailored NBS tools could facilitate and accelerate this process, a comprehensive mapping of their availability and capacity to respond to cities’ challenges is missing. This research aims to provide an overview of tools that intend to facilitate the uptake of NBS for urban climate adaptation supporting cities in overcoming their challenges. To do so, this paper (i) presents the results of interviews and workshops with municipal officers and decision-makers from different European cities that identified the challenges they experience with NBS uptake; (ii) selects and reviews NBS tools and (iii) analyzes them on their capacity to address these implementation challenges. Our research revealed four key challenges that municipal officers experience: resources availability; level of expertise, know-how or competence; the institutional setting, and collaborative governance and planning. The results from the tools’ review show that existing tools can support overcoming a lack of expertise (31), but, to a smaller extent, can also be of use when experiencing the institutional setting (13), availability of resources (11), and collaborative governance and planning (10) as a challenge. This work provides researchers and tool developers with insights into potential market saturation as well as scarcity of certain types of tools that would match cities’ challenges, highlighting needs and opportunities for new tool development.

Comparison of Ecohydrological and Climatological Zoning of the Cities: Case Study of the City of Pilsen

Standardized delimiting of local climate zones (LCZ) will be better applicable to the urban adaptation to climate change when the ecohydrological properties of LCZ units are known. Therefore, the properties of LCZ units based on the methodology of ecohydrological zoning of the urban landscape, which was created in GIS as a basis for planning blue-green infrastructure of cities in the Czech Republic, are presented in the paper. The goal of this study is to compare approaches and results of our own ecohydrological zonation and standardized LCZ delimiting in the city of Pilsen. Both methodological approaches differ in input data, resolution details and parameters used. The results showed that the areas of the individual LCZ classes show different levels of ecohydrological qualities. Internal heterogeneity of LCZ classes demonstrated by variance of ecohydrological parameters’ values can be partly explained by different techniques and data sources for delimitation of both zonations, but by different sets of delimitation criteria. The discussion is held on the importance of terrain slope for supplementing the LCZ classification. A case study can be a stimulus for further development of holistic urban zoning methodologies that would take into account both climatological and ecohydrological conditions.

Effects of Densification on Urban Microclimate—A Case Study for the City of Vienna

Climate adaptation, mitigation, and protecting strategies are becoming even more important as climate change is intensifying. The impacts of climate change are especially tangible in dense urban areas due to the inherent characteristics of urban structure and materiality. To assess impacts of densification on urban climate and potential adaptation strategies a densely populated Viennese district was modeled as a typical sample area for the city of Vienna. The case study analyzed the large-scale densification potential and its potential effects on microclimate, air flow, comfort, and energy demand by developing 3D models of the area showing the base case and densification scenarios. Three methods were deployed to assess the impact of urban densification: Micro-climate analysis (1) explored urban heat island phenomena, wind pattern analysis (2) investigated ventilation and wind comfort at street level, and energy and indoor climate comfort analysis (3) compared construction types and greening scenarios and analyzed their impact on the energy demand and indoor temperatures. Densification has negative impacts on urban microclimates because of reducing wind speeds and thus weakening ventilation of street canyons, as well as accelerating heat island effects and associated impact on the buildings. However, densification also has daytime cooling effects because of larger shaded areas. On buildings, densification may have negative effects especially in the new upper, sun-exposed floors. Construction material has less impact than glazing area and rooftop greening. Regarding adaptation to climate change, the impacts of street greening, green facades, and green roofs were simulated: The 24-h average mean radiant temperature (MRT) at street level can be reduced by up to 15 K during daytime. At night there is only a slight reduction by a few tenths of 1 K MRT. Green facades have a similar effect on MRT reduction, while green roofs show only a slight reduction by a few tenths of 1 K MRT on street level. The results show that if appropriate measures were applied, negative effects of densification could be reduced, and positive effects could be achieved.

A Preliminary Study on the Impact of Landscape Pattern Changes Due to Urbanization: Case Study of Jakarta, Indonesia

Urbanization is changing land use–land cover (LULC) transforming green spaces (GS) and bodies of water into built-up areas. LULC change is affecting ecosystem services (ES) in urban areas, such as by decreasing of the water retention capacity, the urban temperature regulation capacity and the carbon sequestration. The relation between LULC change and ES is still poorly examined and quantified using actual field data. In most ES studies, GS is perceived as lumped areas instead of distributed areas, implicitly ignoring landscape patterns (LP), such as connectivity and aggregation. This preliminary study is one of the first to provide quantitative evidence of the influence of landscape pattern changes on a selection of urban ecosystem services in a megacity as Jakarta, Indonesia. The impact of urbanization on the spatiotemporal changes of ES has been identified by considering connectivity and aggregation of GS. It reveals that LP changes have significantly decreased carbon sequestration, temperature regulation, and runoff regulation by 10.4, 12.4, and 11.5%, respectively. This indicates that the impact of GS on ES is not only determined by its area, but also by its LP. Further detailed studies will be needed to validate these results.

Planning green infrastructure placement based on projected precipitation data

Continued urbanization has led to tremendous changes on the landscape. These changes have exacerbated the effects of extreme climatic events such as flooding because of constrained water infiltration and increased surface flow. Typical runoff control measures involve sophisticated gray infrastructure that guide excess surface flow into storage and disposal sites. In a dynamic climate system, these measures are not sustainable since they cannot be easily modified to accommodate large volumes of runoff. Green Infrastructure (GI) is an adaptable technique that can be used to minimize runoff, in addition to offering an array of additional benefits (urban heat regulation, aesthetics, improved air quality etc.). Strategic placement of GI is key to achieving maximum utility. While physical site characteristics play a major role in determining suitable GI placement sites, knowledge of future precipitation patterns is crucial to ensure successful flood mitigation. In this paper, suitable GI sites within the city of Knoxville, Tennessee, were determined based on potential impact of an extreme flood event as indicated by site characteristics. Then, the relative potential likelihood of a flood event was determined based on projected precipitation data and knowledge of existing flood zones. By combining potential impact with likelihood information, low, medium, and high priority GI implementation sites were established. Results indicate that high priority sites are in the central parts of the city with priority decreasing outward. The GI prioritization scheme presented here, offers valuable guidance to city planners and policy makers who wish to exploit the GI approach for flood mitigation.

Platform Dedicated to Nature-Based Solutions for Risk Reduction and Environmental Issues in Hilly and Mountainous Lands

In the context of global changes, nature-based solutions (NBSs) increasingly draw attention as a possible way to reduce disaster risk associated with extreme hydro-meteorological events while providing human well-being and biodiversity benefits at the same time. The PHUSICOS platform is dedicated to gather and analyse relevant NBSs used to reduce disaster risk associated with extreme hydro-meteorological events in mountainous and hilly lands. To design the platform, an in-depth review of 11 existing platforms has been performed. The PHUSICOS platform currently references 152 literature NBS cases and is continuously enriched through the contribution of NBS community. The platform also proposes a qualitative assessment of the NBSs collected according to 15 criteria related with five ambits: “disaster risk reduction”, “technical and economical feasibility”, “environment”, “society”, and “local economy”. This paper presents the structure of the platform and a first analysis of its content.

Evaluation of Green and Grey Flood Mitigation Measures in Rural Watersheds

Floods cause considerable damages worldwide and mitigation of their adverse effects through effective protection measures is needed. Along with the commonly applied “grey” infrastructure, “green” measures that can offer additional benefits, such as ecosystem services, are increasingly being considered lately. While the recent research tendencies are focused on the effectiveness and the value of green measures in urban areas, this paper presents a comprehensive financial evaluation of green and grey flood mitigation scenarios for a smaller rural watershed. A micro-scale damage model that builds on the hydrodynamic modeling of hazard, detailed asset identification, and damage assessment is presented and applied for evaluation of benefits from various flood mitigation measures in the Tamnava watershed in Serbia. Four scenarios are considered: (1) existing flood protection system; (2) green scenario involving new detention basins; (3) grey infrastructure enhancement by rising of the existing levees and diverting flood discharges; and (4) green-grey scenario that combines scenarios (2) and (3). The benefits (loss reduction) are the greatest with the green scenario and marginally higher with the combined green-grey scenario. The results suggest that for small rural watersheds, a holistic, integrative approach that includes both types of infrastructure can provide the most effective flood risk mitigation.

Investigating Tradeoffs of Green to Grey Stormwater Infrastructure Using a Planning-Level Decision Support Tool

Integrated decision support tools are needed to investigate the tradeoffs of stormwater control measures (SCMs) and determine the optimal suite of SCMs based on the needs of watersheds. In this study, an urbanized watershed undergoing infill development (the Berkeley neighborhood located in Denver, CO, USA) was modeled using a modified version of the U.S. Environmental Protection Agency’s (EPA) System for Urban Stormwater Treatment and Analysis IntegratioN (SUSTAIN). The primary goal was to compare the relative performance between green and grey SCMs, use optimizations and a planning-level approach to assist in decision-making, and discuss how stakeholder and community preferences can shift which SCMs are optimal for the watershed. Green and grey SCMs have variable hydrologic performance based on design and function, and both offer benefits that may be important to decision makers. Our results showed that infiltration trenches and underground infiltration were optimal for reducing flow volumes while vegetated swales and underground detention were optimal for pollutant concentration reduction. Stakeholders value both of these benefits and so the optimal stormwater solution in the Berkeley neighborhood included a mix of green and grey SCMs. Determining the optimal SCMs while considering tradeoffs in costs and associated benefits was complex and multifaceted. Modeling results such as those presented here are critical for informing stakeholders’ decision-making process.

Identification and Pre-Assessment of Former Watercourses to Support Urban Stormwater Management

The application of blue and green infrastructure in urban stormwater management has attracted increasing interest in recent years. At the same time, one can observe a heavy modification of urban watercourses by land reclamation measures aiming at canalizing, straightening, and draining existing water systems at many places around the world. In the context of sustainable urban development, the question arises, whether the reactivation of former watercourses could be an additional option to support urban stormwater management. This article introduces a process to identify former watercourses and to pre-assess their suitability to support urban stormwater management considering different hydraulic functionalities and stormwater related criteria. To prove the practicability of the approach, it was applied in a case study. Our investigations revealed that the reactivation of former watercourses can provide additional opportunities towards more nature-based and sustainable stormwater management in the urban fabric.

Fifty Shades of Blue: How Blue Biotechnology is Shaping the Bioeconomy

The bioeconomy is a new paradigm for the sustainable development of society. Novel uses of blue bioresources and biotechnology solutions, co-created with value chain stakeholders, accelerate the bioeconomy, foster innovation, and promote novel circular business models. Bottom-up approaches sharing visions, needs, and expertise are key to the successful implementation of bioeconomy initiatives.

Measuring and Integrating Risk Management into Green Innovation Practices for Green Manufacturing under the Global Value Chain

How to solve the contradiction between economic growth and ecological environmental protection is a practical problem that should be solved urgently at present. The development of green technology in the manufacturing industry must rely on technology innovation. However, the process of implementing green innovation in the manufacturing industry is full of high uncertainty and risk. First, the green innovation risks were divided into global green R&D risk, global green manufacturing risk, global green marketing risk, and global green service risk from the perspective of the process. Then, this study established a management criteria system of green innovation risk identification in the manufacturing industry under the global value chain (GVC). Furthermore, three methods were applied to identify the green innovation risk of the manufacturing industry under the GVC. Finally, this paper put forward the countermeasures to the green innovation risk of the manufacturing industry under the GVC. The empirical research results of this paper are as follows: From the perspective of the green innovation process, four risks are classified in this study, namely, global green R&D risk, global green manufacturing risk, global green marketing risk, and global green service risk. Among the four stages of green innovation risk, green marketing risk is the highest, followed by green service risk, and green R&D risk and green manufacturing risk are the least. Global green service risk and green R&D risk can be reduced mainly through risk diversification and risk reduction. Global green manufacturing risk and green marketing risk can be reduced mainly through risk diversification and secondary through risk reduction.