Search Results (254)

Urban combined sewer systems are increasingly challenged by climate-intensified rainfall, combined sewer overflows, and receiving-water degradation. This study presents a retrospective evaluation of a hybrid green-gray retrofit program implemented in the Zhenjiang Sponge City pilot watershed, China, where green stormwater infrastructure, drainage network upgrades, and a centralized deep tunnel system were integrated within a densely developed watershed constrained by limited space, low native-soil permeability, shallow groundwater, and aging infrastructure. System performance was evaluated using long-term operational observations, representative hydraulic and water-quality monitoring, municipal operational records, and supporting engineering analyses at both facility and watershed scales. The results demonstrated sustained hydraulic functionality after 7–10 years of operation, with approximately 90% of the monitored bioretention systems maintaining effective infiltration rates greater than 80 mm h⁻¹. Event-based monitoring indicated substantial reductions in runoff volume and pollutant loads, including TSS, COD, NH₃–N, and TP. Following implementation, annual combined sewer overflow occurrence at major outfalls decreased from 318 to 24 events, representing a 92.5% reduction. Supporting engineering analyses indicated that green stormwater infrastructure retrofits alone reduced overflow frequency by approximately 41.8% and overflow volume by approximately 61.1%, while integration with deep tunnels increased reductions to approximately 58.8% and 85.3%, respectively. Official receiving-water monitoring records further indicated that Class III or better water-quality conditions were maintained during approximately 74.7% of the monitored days between 2021 and 2026. These findings provide long-term watershed-scale evidence that hybrid green-gray retrofit strategies can integrate green stormwater infrastructure with centralized overflow regulation to achieve sustained overflow reduction and receiving-water improvement in highly constrained urban watersheds. Full article

Ecological porous concrete (EPC) offers both structural performance and ecosystem services, yet an inherent contradiction exists between the ecological benefits of high porosity and mechanical performance. Traditional design methods focusing solely on macro-scale porosity fail to achieve synergistic optimization. This review comprehensively synthesizes the intrinsic correlations between EPC’s multi-scale pore structures and key properties from micro-, meso-, and macro-scale perspectives, drawing upon representative studies across experimental, numerical, and theoretical approaches. The microscale reveals interfacial transition zone bonding, capillary pore effects, and alkalinity regulation for vegetation compatibility. The mesoscale clarifies the control of effective porosity, tortuosity, and pore throats on fluid transport and root penetration. The macro-scale analyzes skeletal pore support for plant growth, hydrology, and slope stability. A cross-scale collaborative design approach is proposed, featuring microscopic reinforcement, mesoscopic continuity, and macroscopic moderation. This paper provides theoretical support for EPC’s transition from empirical to precision design, promoting low-carbon and large-scale applications in revetments, Sponge Cities, and slope restoration. Full article

Sustainable Urban Drainage Systems (SuDSs) represent a contemporary and eco-friendly method for managing surface water, with the goal of reducing flooding impacts while preserving the environment and enhancing water quality and biodiversity. In Bari, recurrent flooding stemming from water stagnation, extreme weather, and urban development poses challenges to sustainable growth. This study applies the ‘Sponge city’ concept to address these issues through an evaluation of current urban permeability and the implementation of Nature-Based Solutions (NBSs) to reduce runoff and manage underground flows. By assessing the climatic conditions and hydrological factors contributing to urban stagnation, this project seeks to create a resilient urban environment capable of adapting to climate change and effectively mitigating both significant and minor rainfall events. It aims to reduce runoff, while also promoting groundwater recharge and alleviating saline contamination effects in coastal areas, ultimately enhancing the safety and livability of urban landscapes. Full article

Due to climate change and rapid urbanization, cities worldwide face the dual challenge of improving flood resilience and providing accessible green space within limited land resources. Sponge City parks offer a landscape-based approach for integrating stormwater management with park services. However, how park morphology structures this combined performance remains insufficiently understood. This study examines 26 Sponge City parks in Shanghai and evaluates how node-, line-, and patch-type morphologies are linked to stormwater storage and service provision. Using geospatial analysis, DEM-derived catchment delineation, land-cover interpretation, and statistical analysis, this study compares estimated stormwater storage, storage efficiency, local park availability, and land-cover composition across different park morphologies. The results show that estimated performance of stormwater management and park service provision vary across morphological types, but these differences do not follow a simple node–line–patch hierarchy. Rather, the observed patterns are jointly shaped by park morphology, catchment setting, land-cover allocation, and surrounding urban context. These findings suggest that Sponge City parks should not only be evaluated by total stormwater storage. Their contribution depends on morphology, scale, catchment setting, land-cover allocation, and urban context. The study provides a morphology–performance perspective to support more differentiated planning of multifunctional green infrastructure. Full article

Against the backdrop of rapid urbanization, urban land-resource use faces the dual challenge of improving efficiency while maintaining ecological sustainability. Enhancing urban land green use efficiency contributes to the achievement of the United Nations Sustainable Development Goals, particularly SDG 11 and SDG 15. As an emerging governance approach for urban green infrastructure, the National Sponge City Policy (NSCP) aims to address urban waterlogging through nature-based solutions while improving land multifunctionality and ecological carrying capacity. Based on city-level panel data from 2005 to 2022, this study employs a difference-in-differences (DID) approach to identify the policy effect of the NSCP on ULGUE and further examines three transmission channels: innovation effects, infrastructure-support effects, and population-agglomeration effects. The novelty of this study lies in integrating the NSCP into the analytical framework of urban land green use efficiency, extending previous research that mainly focused on waterlogging control, water-resource management, and ecological benefits, and further developing a “policy intervention-factor reallocation-ULGUE improvement” mechanism pathway. The empirical results show that the NSCP significantly improves land green use efficiency in pilot areas, and this conclusion remains valid across multiple robustness checks. The mechanism analysis indicates that strengthened green innovation capacity, improved green infrastructure, and population agglomeration are key channels through which the policy effect is realized. Heterogeneity analysis further reveals that the policy effect varies across regions, dominant industrial structures, and industrial-base types. Overall, the NSCP promotes green spatial governance and efficient resource utilization, providing important institutional experience for coordinating ecological protection and urban development. Full article

Public parks are increasingly expected to function not only as recreational green spaces but also as components of urban green stormwater infrastructure. In practice, however, their performance is still commonly judged by stormwater storage capacity alone, a project-level metric that tends to favor larger parks and obscure differences in how parks contribute to broader blue-green stormwater systems. Accordingly, this study aimed to develop and apply an exploratory comparative framework for assessing the differentiated stormwater roles of sponge city parks beyond storage capacity alone. Using 20 sponge city parks in Shanghai as cases, the framework integrates stormwater storage capacity, storage efficiency, flow leverage, and facility configuration. The results show that annual stormwater storage capacity varied substantially across the 20 parks, ranging from 7625.12 m³ to 132,915.24 m³, with a mean value of 47,220.80 m³. However, this capacity-based ranking was strongly associated with park area. Once storage was normalized by area, the ranking changed markedly: line-type parks showed the highest mean storage efficiency of 1.393, followed by node-type parks at 0.921, whereas patch-type parks recorded a much lower mean value of 0.059. Flow leverage scores ranged from 0 to 6, with a mean value of 2.35, indicating that parks with comparable storage performance may occupy different hydrological positions within the broader topographic flow structure. The preliminary capacity-leverage typology further showed that high storage capacity did not always coincide with high hydrological leverage, and facility configuration scores ranged from 1 to 5, suggesting additional variation in internal infrastructural organization. These findings suggest that storage capacity should be complemented by spatial efficiency, hydrological position, and facility configuration when interpreting the differentiated stormwater roles of sponge city parks. The study reframes evaluation from a single project-level storage metric toward a more differentiated understanding of sponge city parks as urban green stormwater infrastructure and supports more sustainable assessment of community-scale stormwater management within broader blue-green systems. Full article

The rapid growth of the low-altitude economy and urban air mobility (UAM) is reshaping urban transport and infrastructure systems. However, current planning practices still tend to treat green spaces, stormwater facilities, and drone infrastructure as separate subsystems. This paper proposes a Garden Hydrology UAV collaborative infrastructure framework for resilient urban low-altitude logistics and inspection. Pocket parks and sponge city facilities (rain gardens, detention basins) are redesigned as multi-functional UAV bases that integrate take-off/landing and charging with stormwater retention and recreation. A SWMM-based hydrological model provides time-varying inundation and storage states, which are mapped into dynamic node availability constraints for UAV operations, using EPA SWMM 5.2. A multi-objective optimization model is formulated to minimize logistics operation cost, hydrological risk exposure and noise impact on sensitive receptors, while respecting airspace and battery constraints. A stylized 4 km² high-density district is used to evaluate three scenarios: depot-only operations, garden–UAV integration without hydrological coupling, and the full collaborative framework with SWMM-based node availability and high-precision navigation. Simulation results show that the integrated design reduces makespan by up to 19.7%, energy use by 22.3%, and hydrological risk exposure by 63.4%, while lowering noise exposure by 21.3%, relative to the baseline. The study suggests that garden and sponge city infrastructures can become key physical supports of smart low-altitude networks under the low-altitude economy. Full article

Urbanization and climate change are increasing pluvial flooding risks, thereby intensifying the need for more adaptive stormwater governance in Chinese Sponge City projects. Although public participation is widely recognized as important, current research frequently conceptualizes it as a simplified or static attribute and seldom provides explicit criteria for identifying representative projects in large urban portfolios. This study develops a life cycle-sensitive framework for evaluating public participation in Sponge City projects by conducting a cross-city comparison in China. The study integrates project inventory construction, evidence-based representative project selection, and a multidimensional participation measurement tool covering breadth, depth, identity, and potential across planning, design, construction, and maintenance using five national pilot cities: Jinan, Shanghai, Xiamen, Shenzhen, and Wuhan. The results show that the five representative projects display distinct life cycle participation profiles, rather than a single participation pattern, influenced by project type and governance arrangement. Maintenance emerges as the strongest documented stage, whereas design is the weakest, suggesting stronger documented governance continuity after project delivery than in front-end co-design. Recurrent weaknesses remain in substantive inclusion and feedback-adoption closure. Overall, the study frames participation as a structured governance capability, providing an auditable comparative framework for identifying participation strengths and weaknesses in Sponge City governance. Full article

Amid rapid urbanisation and the associated environmental challenges, such as increased flood risk, the urban heat island effect, and ecosystem degradation, Blue–Green Infrastructure (BGI) has emerged as a vital sustainable development strategy. Some countries have successfully implemented BGI projects, shaped by their unique geographical conditions, socioeconomic contexts, and governance structures. Although the BGI concept is highly relevant worldwide, strategies for integrating BGI into urban environments vary significantly across regions and countries due to their distinct urban structures and spatial planning systems. This study provides a comparative study of BGI implementation into spatial planning systems of Ljubljana (Slovenia) and Kraków (Poland), as Central European cities, and Shanghai and Guangzhou, as Chinese cities. Through a systematic analysis of semi-structured interviews with key stakeholders, the study evaluates how different enablers, i.e., (1) guidelines, strategies, and actions, (2) land-use strategy for BGI, and (3) potential of factors for BGI implementation, including planning scale, financial, technical, and spatial, facilitate BGI implementation. This comparative study reveals contrasting yet complementary BGI paradigms, most notably related to top-down versus bottom-up implementation and different prioritisation of BGI functions. These varying paradigms are shaped by specific urban challenges, governance, and spatial planning systems. Full article

This study develops a ternary Fe-based geopolymer system composed of metakaolin (MK), red mud (RM), and fly ash (FA) for the preparation of sustainable water-retaining subgrade materials for sponge-city roadbed applications. Unlike conventional formulations primarily designed for structural strength or rapid permeability, the proposed MK–FA–RM system was designed to improve water-storage capacity while maintaining adequate mechanical support and environmental compatibility. In this ternary system, MK provides highly reactive aluminosilicate species for geopolymer network formation, RM introduces Fe-bearing phases and enhances industrial solid-waste utilization, and FA contributes to particle packing, workability, and resource efficiency. A constrained ternary mixture design implemented using Design-Expert software was adopted to optimize precursor proportions. Within the investigated compositional range, the fitted first-order mixture model showed acceptable statistical adequacy for preliminary composition screening (R² = 0.86). The optimal blend (60% MK, 30% RM, and 10% FA) achieved a 7-day compressive strength of 8.37 MPa and a water retention rate of 35.3% under ambient curing conditions, satisfying the strength requirement considered for the target subgrade/base-layer application. Microstructural and phase analyses suggest that the synergistic interaction of the three precursors promoted Fe-modified aluminosilicate gel formation together with conventional geopolymer gel products, while improving matrix continuity and preserving interconnected pore space for water storage. This multiscale structural effect helps explain how the material achieved a balance between water retention capacity and mechanical support. Under the tested conditions, the material maintained acceptable residual strength after short-term exposure to water, acid, and sulfate-containing solutions. Life-cycle assessment indicated a 70% reduction in CO₂ emissions compared with ordinary Portland cement, while pilot-scale cost analysis showed a 39% lower production cost than MetaMax-based geopolymer materials. Pilot-scale application further demonstrated the constructability and water-regulation potential of the material in practical environments. Overall, the proposed ternary Fe-based geopolymer demonstrates that Fe-rich industrial wastes can be engineered into low-carbon and economically viable water-retaining subgrade materials that balance hydraulic regulation, structural adequacy, and sustainability. Nevertheless, long-term durability, cyclic loading performance, and direct nanoscale characterization of Fe-bearing gel evolution still require further investigation. Full article

Urban pluvial flooding is becoming more severe in rapidly urbanizing cities under increasingly frequent extreme rainfall. Although Low Impact Development (LID) is widely used to improve infiltration and on-site stormwater retention, its hydrological performance may differ greatly across urban functional zones with distinct land-cover patterns, development intensity, and retrofit constraints. To address the lack of comparative evidence under consistent conditions, this study mapped land cover in five representative functional zones in Nanjing—old residential, new residential, commercial, industrial, and cultural/educational areas—and applied a unified CITYgreen (SCS-CN) framework under a 72 mm, 24 h, two-year design storm to simulate four standalone LID measures: ground-level greening, permeable pavement, green roofs, and grassed swales. Results showed big zone-dependent differences in hydrological benefits. Runoff reduction was greatest in highly impervious industrial and commercial areas, whereas the new residential zone showed only a marginal improvement due to its relatively favorable baseline retention conditions. Across all zones, measures that enhanced infiltration and near-surface storage performed best, with ground-level greening and permeable pavement achieving the highest retention efficiency. These findings highlight the importance of zoning-based, context-sensitive LID prioritization for urban renewal, sponge-city retrofitting, and stormwater planning in rapidly urbanizing cities. Full article

The sponge city pilot policy (SCP) is a green infrastructure initiative that integrates ecological stormwater management, land-use planning, and urban sustainability goals. This study employs the super-efficiency slack-based measure (SBM) model to evaluate the green total factor productivity (GFP) of 278 prefecture-level and above cities in China from 2010 to 2022. It then applies a difference-in-differences (DID) model to identify the causal effect of the SCP on urban GFP while further examining transmission mechanisms and heterogeneous policy effects. The empirical findings show that: (1) the SCP significantly enhances urban GFP, with pilot cities exhibiting an average increase of approximately 6.08% relative to non-pilot cities, indicating broader medium- to long-term ecological–economic co-benefits beyond the policy’s immediate hydrological objectives; (2) the policy effect is more pronounced in cities with stronger economic foundations, larger urban scales, greater environmental governance pressure, weaker resource dependence, and more favorable locational conditions; and (3) the SCP promotes industrial structure transformation (IST) and green technological innovation (GTI), which jointly mediate the relationship between ecological infrastructure and green productivity. Drawing on ecological modernization theory and structural change theory, this study explains how ecological infrastructure, as a techno-structural reform mechanism, can internalize environmental externalities, stimulate innovation, and facilitate sustainable urban transformation. These findings provide evidence that green infrastructure policies can generate both ecological and economic co-benefits, offering useful insights for climate-resilient and sustainable urban planning. Full article

High-density urban areas face a critical trade-off between limited land resources and intensifying flood risks. This study develops a grey-green infrastructure (GGI) optimization framework that integrates hazard–exposure–vulnerability (H-E-V) risk assessment, surrogate modelling, and NSGA-III to simultaneously minimize cost, maximize flood control, and enhance water environmental benefits. The Suqian City case study reveals: (1) Grey-green coupling significantly outperforms single green infrastructure (GI), providing an additional 7.07–23.34 percentage points in flood risk control rate (FRCR). While GI reaches a performance bottleneck at 78.59% FRCR under extreme events, the GGI configuration maintains a high efficiency of >92.74%. (2) Risk-informed spatial targeting effectively reclassifies urban vulnerability. Under a 20-year return period, high-risk and medium-high risk areas are reduced by 80.99% and 52.15%, respectively. The validated surrogate models ensure high optimization efficiency with $R^2$ values exceeding 0.85. This framework provides a methodologically transferable decision-support tool for sponge city construction, demonstrating that strategic spatial allocation is as vital as infrastructure capacity for urban flood risk management. Full article

High-density cities face dual challenges of aging populations and climate change, driving widespread renewal of aging residential communities. Current practices, however, often treat sustainability goals (e.g., energy efficiency, carbon reduction) and age-friendly design objectives (e.g., accessibility, social inclusion), often guided by frameworks like the World Health Organization’s (WHO) age-friendly cities initiative, as separate or conflicting agendas, leading to fragmented policies and suboptimal outcomes. This study addresses this gap by proposing and testing a framework for “Sustainable-Age-friendly Coordinated Renewal” (SACR). Through a mixed-methods case study of a typical old community in the humid subtropical city of Guangzhou, China, we investigate how green infrastructure and low-carbon interventions can be synergistically designed to enhance both environmental performance and the well-being of elderly residents. A “Coordinated Renewal Strategy Package” was developed, incorporating ecological shading, sponge city facilities, energy retrofits, and accessible slow-traffic systems. Post-intervention simulation and evaluation indicated significant improvements in microclimate (e.g., reduced mean radiant temperature and Physiological Equivalent Temperature (PET)) and marked increases in outdoor activity duration and social interaction frequency among elderly residents. This study concludes that a human-centric, needs-based design approach is key to unlocking synergistic benefits. The proposed SACR framework and evaluation matrix offer a practical tool for urban planners, architects, and policymakers to holistically assess and implement community renewal projects, contributing to more resilient, inclusive, and sustainable urban futures by addressing localized challenges like the Urban Heat Island (UHI) effect. Full article

Rapid urbanization-induced extreme rainstorms severely disrupt social functions. Previous research often focused on “de-densification” strategies, which are difficult to adapt to high-density Sponge City Stormwater Management Units (SMUs) that carry core development functions. This study uses Shenzhen as a case study, utilizing Keep movement big data as a “social sensor” for system function perception and introducing the Socio-Ecological-Technological Systems (SETS) theory to construct a “recovery (RCN)–resistance (MI)” binary assessment framework. Through systematic clustering and hierarchical regression models, the driving mechanisms of blue landscape patterns, topography, road networks, and the built environment on social behavioral resilience are systematically parsed. The results show: (1) Road network morphology dominates resistance, while multi-dimensional elements collaborate for recovery. Resistance (MI) is primarily dominated by macro road network detour resistance (TPD2000, β = 0.956), while recovery depends on the synergistic support of blue space interspersion (Blue_IJI), topography, and micro-circulation road networks. (2) Green infrastructure fails in the model due to efficiency bottlenecks, empirical evidence of weakened regulation caused by green space fragmentation in ultra-high-density environments. (3) Low-density, eco-centric built environments provide dual synergistic gains for resilience. Based on this, a “Bidirectional Socio-Ecological Resilience Needs Pyramid” model is constructed, identifying four governance types such as the “Synergistic Balanced Type”. This study provides a quantitative basis for the transition from administrative control to precise morphological governance in high-density cities. Full article