“Sponge City” Viability: Perspectives from Practitioners and Domain Experts in China

Abstract

China’s “Sponge City” initiative, launched in 2014, is a transformative approach to urban stormwater management that aims to deliver multiple benefits through nature-based solutions. Despite its widespread adoption in China, questions remain regarding its long-term viability. Through a new conceptual framework, this study examines the viability of the Sponge City model by analyzing insights from 30 practitioners and domain experts working in Beijing, Shanghai, and Shenzhen. Drawing on semi-structured interviews and field studies, it investigates how participants interpret the concept, integrate climate adaptation strategies, and assess effectiveness across six dimensions: governance, economy, environment, urban form, civic engagement, and human wellbeing. The findings reveal diverse perspectives shaped by local contexts, disciplinary backgrounds, and professional experiences. While participants expressed cautious optimism, they also identified persistent challenges, including funding constraints, fragmented planning processes, and insufficient public engagement. Climate adaptation emerged as a central concern, with mixed views on the initiative’s ability to address extreme weather events. Overall, the study suggests that the Sponge City model holds promise, but its viability depends on continued refinement, interdisciplinary collaboration, and adaptive governance tailored to local needs. This study offers insights to inform future practice and broaden global efforts in stormwater management and urban resilience.

1. Introduction

In China, rapid urbanization and human-induced climate change have exacerbated the “city syndrome” in many urban areas [1], leading to issues such as urban flooding, water scarcity, and water pollution, among others. The concept of “Sponge City” has emerged as an innovative approach to urban stormwater management in China, gaining significant attention worldwide [2,3]. The term Sponge City is a metaphor for the way urban areas can collect, store, and reuse rainwater, much like a sponge absorbs and releases water. The Sponge City model aims to mitigate urban flooding, reduce urban water pollution, and utilize rainwater resources, as well as restore urban water’s ecological functions through the implementation of nature-based solutions [4].

The Sponge City initiative in China, launched by the central government in 2014, has mobilized extensive expertise to achieve an ambitious national goal: by 2030, 80% of the country’s built urban areas should be able to absorb and reuse at least 70% of stormwater on-site [5]. In 2015, the Ministry of Housing and Urban-Rural Development formed the national Sponge City Construction Technical Guidance Specialist Council, including 37 specialists in hydrology, meteorology, planning, engineering, architecture, landscape architecture, and finance [6]. Provincial and municipal councils soon followed. For example, Sichuan Province appointed 48 specialists in 2016 [7], while the City of Chongqing certified 145 city-level specialists in 2020 with a five-year term [8].

Over the past decade, China’s Sponge City model has been widely adopted nationwide [9]. Practitioners and domain experts have accumulated extensive first-hand experience, contributing valuable lessons and examples of best practices. Yet despite this substantial body of practice-based knowledge, their perspectives remain underexamined in the broader Sponge City discourse. Meanwhile, the long-term viability of the Sponge City model faces scrutiny, particularly regarding its performance in preventing flooding risks [10], adaptive governance [11], long-term operation and maintenance [12], and the diverse ecological and socioeconomic challenges across cities [13,14]. Given the value of their practical knowledge and expertise on this subject, foregrounding the perspectives and insights of practitioners and domain experts may strengthen the long-term viability of Sponge City implementation, which, in turn, can promote urban livability and better outcomes for communities.

1.1. Key Definitions and Conceptual Framework

To establish the scope of this study, a few key definitions are necessary. In this study, Sponge City refers to an ambitious planning policy and design practice in China that relies primarily on nature-based solutions to manage stormwater amid climate change and rapid urbanization. Sponge City viability is defined as the ability of Sponge City systems to manage urban stormwater effectively and sustainably as a workable solution to mitigate flooding, reduce water pollution, alleviate water scarcity, and generate environmental, economic, social, and human co-benefits.

For the purpose of this study, practitioners refer to professionals directly involved in the planning, design, implementation, or management of Sponge City projects, including urban planners, architects, landscape architects, engineers, construction managers, and government officials. Domain experts or experts are defined as individuals who are either officially recognized as Sponge City specialists at the national, provincial, or municipal level, or senior professionals with at least 10 years of experience in Sponge City or relevant stormwater management approaches, such as the “Shan-Shui” (mountain-water) landscape practice [15].

This study introduces a conceptual framework for assessing Sponge City viability. Sponge City planning and practice can be placed under the umbrella of sustainable development, which emphasizes the interconnected roles of environment, economy, society, and people [16]. Building on these sustainability principles, the framework offers a holistic lens for evaluating challenges and opportunities across six dimensions: environment, economy, governance, urban form, civic engagement, and human wellbeing, forming a coherent structure that reflects both theoretical foundations and practical considerations. These dimensions are interrelated rather than being mutually exclusive. Figure 1 below presents the conceptual framework diagram.

1.2. Literature Review

In recent decades, urban stormwater management has shifted from conventional gray infrastructure designed to rapidly convey runoff off-site to low-impact development (LID) strategies that mimic natural hydrology and manage stormwater at its source [17,18]. Since the early 2000s, LID has gained widespread acceptance as an ecologically sound approach to control runoff quantity and quality [1]. China’s Sponge City initiative was modelled on LID principles, as outlined in the City Construction Technical Guide—Low-Impact Development Rainwater System Construction (Trial), issued by the Ministry of Housing and Urban-Rural Development [19]. Before the “Sponge City” initiative was launched in 2014, Chinese scholars had already conducted research on LID measures [20,21]. Chinese practitioners had implemented LID projects in cities like Beijing, Shenzhen, and Jiaxing [20,22]. One example is the Beijing Olympic Forest Park and Olympic Village, built in 2008, mitigating urban stormwater runoff with LID measures [23].

Although the Sponge City is a widely disseminated concept in China, it is a contentious topic among researchers and practitioners. Some see it as the best and most cost-effective way for cities to adapt to climate change [24], while others regard it as highly political, arguing that the concept has been misappropriated by some local authorities and builders as a trendy brand and slogan [25]. Some experts, such as the late Dr. Kongjian Yu, founder of Turenscape, believed that the benefits of the Sponge City approach, which involves designing and constructing citywide systems of ponds, wetlands, and parks to retain stormwater, were well established [25], while others have serious concerns about its effectiveness. Zhou and Penning-Rowsell [26] interviewed seven professionals (n = 7) in Yangzhou on the feasibility of constructed wetlands for Sponge City flood mitigation, including engineers, local officials, policy advisors, and researchers with first-hand experience. While valuing the concept, participants doubted its viability due to size, capacity, space constraints, and economic sustainability. They also questioned rain gardens and green roofs, citing limited storage and rapid saturation during heavy rain.

A Web of Science (WoS) topic search using truncated keywords Chin* AND “Sponge Cit*” yielded 583 publications as of 18 October 2025. Narrowing the search to include the keywords Expert* OR Practitioner* further limited the results to 11 publications. Among them, only five WoS-indexed articles explicitly examined perspectives from practitioners and experts, often through interviews or surveys alongside other stakeholders.

Li et al. [14] in 2017 investigated the progress of all 30 Chinese pilot Sponge Cities launched in 2015 and 2016 through document reviews, site visits, and surveys with more than 200 participants (n = 200+), including scholars, practitioners, government officials, residents, and other local stakeholders. This study identifies a broad array of challenges, from technical, physical, regulatory, and financial, to community and institutional, such as overly ambitious stormwater retention targets, uniform application of LID measures, lack of local calibration, fragmented governance, unclear responsibilities, and financing gaps. Opportunities include context-specific standards, interagency coordination, professional training, and valuation of ecosystem services to attract diversified funding.

Hawken et al. [27] surveyed 90 urban water specialists, both in China and Australia, from a variety of industry sectors. According to the Chinese practitioners they surveyed (n = 49) and interviewed via focus groups (n = 20), Sponge City projects in China have generally achieved their fundamental objectives related to drainage and water quality, but they have not sufficiently addressed broader and more complex goals, such as economic capacity, socio-cultural dynamics, and design integration [27].

Three Sponge City experts, civil engineer Nian She, hydraulic engineer Yingxia Xie, and landscape architect Dihua Li, underline in their 2021 reflection several persistent obstacles, including unrealistic public expectations, substandard construction quality, ineffective interagency cooperation, and the lack of whole-process management and routine maintenance [28]. Technical barriers also persist, including outdated engineering mindsets, limited risk assessment, and insufficient emergency planning. In addition, practitioner shortages, heavy reliance on government funding, and lack of market mechanisms all impede growth. Opportunities include integrating green and gray infrastructure holistically, increasing public education, implementing stormwater billing and carbon trading for sustainable finance, and using digital technologies for modeling.

Wang et al. [29] conducted surveys of 600 residents and interviewed 11 experts (n = 11) to assess green stormwater infrastructure (GSI) in Sponge Cities in China. Public respondents expressed strong trust in government-led initiatives and recognized aesthetic and health benefits but showed limited technical awareness and low participation in planning. Experts likewise acknowledged GSI’s ecological potential, yet emphasized systemic issues, including insufficient integration of social co-benefits, inadequate operations and maintenance, and lack of long-term performance monitoring. They also highlighted opportunities to enhance multifunctionality, expand participatory processes, and strengthen governance measures to support long-term performance beyond initial construction.

In terms of finance, Zhang et al. [30] used expert assessments to examine risks in public–private partnership (PPP) models for funding “Sponge City” projects. Governance-related risks, such as government intervention, inadequate supervision, and immature laws, were identified as the most critical by experts, along with construction risks such as project fragmentation and unclear catchment boundaries, underscoring the need for clearer legal frameworks, standardized guidelines, and incentive mechanisms to improve PPP feasibility and sustainability.

In summary, although discourse on the Sponge City initiative has expanded, research that examines the perspectives of practitioners and domain experts remains limited. Addressing this gap requires more empirical work grounded in first-hand professional experience to clarify the practical implications of the Sponge City initiative and inform its future planning and implementation.

1.3. Study Cities

This study examines Sponge City viability through the lens of practitioners and domain experts in three major cities: Beijing, Shanghai, and Shenzhen. Among the nation’s first 30 pilot cities designated in 2015 and 2016 [31], these three cities were deliberately selected to represent a wide spectrum of geographical and climatic settings, urban development trajectories, and governance models that shape the outcomes of the Sponge City initiative in these metropolitan contexts.

Beijing, the capital of China, has a continental monsoon climate characterized by cold, dry winters and hot, humid summers with convective weather systems that can yield thunderstorms, strong winds, and heavy rainfall [32]. Modernization in Beijing over recent decades has often come at the expense of culturally significant historic neighborhoods. The city has only recently adopted on-site stormwater infiltration and storage standards for new developments [31]. Its mixed urban fabric of old and new complicates retrofitting efforts. Beijing still has a long way to go in realizing its vision of a livable “sponge” capital [33].

Shanghai, a coastal megacity in the Yangtze River Delta, experiences a humid subtropical climate with concentrated seasonal rainfall from April to October [34], making flood control a central priority. The city has integrated Sponge City principles into its comprehensive planning at all levels [35] and developed Sponge City parks to combine stormwater management with public amenities [36]. However, retrofitting older neighborhoods remains difficult due to space and technical constraints.

Shenzhen is China’s “Silicon Valley” on the southeast coast [37]. It experiences a southern subtropical monsoon climate with a long summer and a short winter. Severe weather, such as tropical cyclones, thunderstorms, and heavy rain, frequently occurs [38]. Shenzhen’s explosive urban growth resulted in enormous stormwater management challenges, which required a systematic response. Since 2016, the city has emerged as a national leader in Sponge City development, driven by its innovative spirit and urgent need to address climate risks [39].

Together, Beijing, Shanghai, and Shenzhen provide a diverse and analytically rich set of contexts for assessing the real-world viability of the Sponge City initiative in China. Drawing on insights from practitioners and experts across these three cities, this study assesses the perceived feasibility and scalability of Sponge City planning, design, implementation, operations, and policy oversight.

1.4. Research Questions

Building on the diverse urban settings of the study cities, this inquiry is guided by the conceptual framework introduced in Section 1.1 to evaluate Sponge City viability across six dimensions: environmental performance, economic feasibility, governance capacity, urban-form integration, civic engagement, and human wellbeing. The framework underpins the study’s approach to assessing viability and provides the basis for the following research questions:

RQ1: 

What are the general perspectives of practitioners and domain experts on China’s Sponge City concept and implementation?

RQ2: 

How did climate change considerations influence the planning and design of Sponge Cities, and what strategies were employed to enhance their viability?

RQ3: 

What are the perceived opportunities and challenges affecting Sponge City viability across different dimensions of the conceptual framework?

To answer these questions credibly, this study centers on first-hand professional experience gathered from 30 practitioners and domain experts, ten from each city, whose direct involvement in planning, design, implementation, and management offers critical insight into Sponge City delivery. These perspectives are further enriched by the lead author’s field studies, which help contextualize interview findings, evaluate on-the-ground implementation, and reveal how policies and design intentions materialize in real urban environments.

2. Materials and Methods

This study employed qualitative research methods to assess the viability of the Sponge City initiative in China, drawing on interviews with 30 practitioners and domain experts across three Chinese cities. Qualitative interviews served as the primary mode of inquiry as part of the field research. Relying on asking questions to collect data, an interview study can be an effective way to gain insight into critical social issues by understanding the experiences of individuals whose lives are reflected in those concerns [40]. Semi-structured interviews were adopted, combining a set of open-ended questions with the flexibility to explore specific themes in depth.

All interviews were conducted by the lead author. For the full list of interview questions, see Appendix A. During a month-long field trip to China in July 2024, 90% of the 30 qualitative interviews were conducted face-to-face. Among these 27 in-person interviews, 9 were conducted in Beijing, 10 were conducted in Shanghai, and another 8 were conducted in Shenzhen. Three interviews were held via Zoom remotely in April, July, and August 2024. Each interview lasted about 30 to 60 minutes. For the face-to-face interviews, the researcher met the participants in and outside their professional offices at the locations convenient for them. Snowball sampling is recognized as an effective and purposeful method for accessing diverse and specialized communities [41]. In this study, the initial participants, or “seeds,” were drawn from the lead author’s professional network in China, notably alumni of Tsinghua University, Tongji University, and Beijing University. These groups, including some of China’s most esteemed experts in planning, engineering, hydrology, architectural design, and landscape construction, are renowned for their international ties. These participants then helped identify additional interviewees across a range of organizations and disciplines relevant to Sponge City practice.

2.1. Study Participants

Out of a sample of 30, 10 participants were female, accounting for 33% of the sample. Figure 2 illustrates the participants’ years of experience in stormwater management and gender distribution. Most participants had more than five years of working experience, with nearly half reporting over 20 years in the profession. Eight individuals with “30+ years” of expertise account for a large portion of the sample (27%).

The pool of 30 participants included a diverse range of practitioners and experts who came from various disciplines, including environmental science, hydrology, urban planning, urban design, landscape architecture, architecture, civil engineering, and social work. Figure 3 indicates the participants’ academic backgrounds and professional fields across three different cities. Of the 30 participants, two were recognized as national “Sponge City” specialists, and two were municipal-level “Sponge City” specialists.

The 30 participants worked across a variety of industry sectors, including universities (20%), planning and design institutes (20%), public and private consulting companies (53%), and other government agencies and NGO’s (7%), as shown in Figure 4. This diversity highlights the broad range of expertise and perspectives involved in the study.

2.2. Interview Data Collection and Analysis Process

All face-to-face interviews were audio-recorded using the Voice Memos app on an iPhone and later transcribed using the Transcribe feature in Microsoft 365 Word. Interviews conducted remotely were recorded and transcribed using Zoom. Originally conducted in Mandarin Chinese, the interviews were translated into English with Microsoft Word and proofread by the lead author for accuracy.

The data analysis process in this manuscript was inductive in nature. Raw data sources were categorized, coded, analyzed, and visualized using Microsoft Excel and NVivo 15. For clarity, the manuscript uses the abbreviations Beijing (BJ), Shanghai (SH), and Shenzhen (SZ) when referring to the three case-study cities. Because this research involves human subjects and interviewee identities must be protected, each participant was assigned an anonymized label (e.g., BJ1, BJ2, SH1, SH2, SZ1, SZ2) corresponding to their city. Interview transcripts were coded using the six viability framework dimensions as parent codes. Within each dimension, “challenges” and “opportunities” served as child codes, each containing additional sub-codes for further thematic analysis.

2.3. Field Studies

For triangulation, this study includes fieldwork observations in three cities, as combining interviews with direct site observations enhances validity and provides a richer, context-based understanding. Six stormwater management projects designed or referenced by participants were examined, two in each city, along with general observations of sponge measures along public streets. These visits, conducted in July 2024, are listed in

Table 1. Field Study Project List.

Project Name	Built Year	Project Size	Designer	Primary Sponge Strategies
Beijing Olympic Forest Park	2008	1680 acres (680 ha.)	Beijing Tsinghua Tongheng Urban Planning & Design Institute, Beijing, China	man-made lake, constructed wetland, bio-swale, retention pond, underground cistern, infiltration well, permeable paving
Beijing Liang Ma River Revitalization Project	2021	199.6 acres (80.8 ha.)	AECOM Chinese Mainland, Beijing, China	restored vegetated riverbank, constructed riparian wetland, sunken green space, permeable paving
Shanghai Houtan Park	2010	34.6 acres (14 ha.)	Turenscape, Beijing, China	bio-swale, retention pond, constructed wetland, rain garden, permeable paving
Shanghai Xuhui Runway Park	2020	36.2 acres (14.6 ha.)	Sasaki Shanghai Office, Shanghai, China	constructed wetland, bio-swale, rain garden, permeable paving, underground cistern
Shenzhen Vanke Yuncheng mixed-use development	2019	97.4 acres (39.4 ha.)	Developer: China Vanke Co. Designers: Group design led by Urbanus, Shenzhen, China	green roof, rain garden, permeable paving, sunken green space, underground cistern
Shenzhen East Dike	2019- ongoing	130 km coastline 6 demo areas	KCAP Shanghai, Shanghai, China; and FELIXX, Rotterdam, Netherlands	rain garden, wave garden (beach vegetation and rock), green edge dike, coastal wetland

, and photographs were collected at each site to document the fieldwork.

3. Results

This section summarizes the important findings from interviews with practitioners and experts engaged in the planning, design, implementation, and management of China’s “Sponge City” initiative. The results are structured around three major research questions, each of which addresses a critical aspect of the initiative’s viability. These include professional viewpoints on Sponge City’s overall strategy and execution (RQ1), the impact of climate change concerns on Sponge City planning and design strategies (RQ2), and perceived opportunities and challenges across multiple dimensions of the conceptual framework (RQ3). Collectively, these insights provide a comprehensive picture of the initiative’s strengths, limitations, and long-term viability.

3.1. RQ1: What Are the General Perspectives of Practitioners and Domain Experts on China’s Sponge City Concept and Implementation?

3.1.1. Keyword Analysis

Each participant in Beijing, Shanghai, and Shenzhen was asked to use 3 to 5 keywords describing China’s Sponge City initiative. Figure 5 presents word clouds created on Wordclouds.com with keywords collected from the three sub-groups in each city. Resilient is the most frequently recognized keyword by the participants. Adapted to local conditions, comprehensive, and effective are tied as the second most frequently chosen terms.

Adapted to local conditions was highlighted by participants across all three cities. Effective was mentioned by three out of ten interviewees in Shanghai and once in Beijing, but interestingly, none in Shenzhen. In fact, one Shenzhen participant described China’s Sponge City initiative as “ostentatious but ineffective.” The keyword comprehensive appeared twice in interviews from Shenzhen and Shanghai. In Beijing, while comprehensive was not directly mentioned, a similar term, holistic, was noted by one participant in English.

Following these top keywords, systematic was also frequently cited across all cities. Other recurring terms included nature-based, low-impact, multidisciplinary, and the overarching sentiment captured in the phrase “idealism meets harsh reality.” Negative expressions surfaced as well, such as the Chinese idiom “chicken feathers all over the place”, a metaphor for disorder, mentioned in Beijing and Shanghai. This metaphor conveys practitioners’ frustrations with overall project outcomes, such as fractured execution, dispersed responsibilities, and messy results when systems fail to work together. Additional negative descriptors, such as flawed, fragmented, and unsystematic, reflect concerns about overly ambitious goals, lack of integration, and insufficient planning.

These keywords reveal both shared priorities and divergent perspectives among practitioners and experts on China’s Sponge City planning and implementation.

3.1.2. General Attitudes

The general attitudes of the 30 participants toward the Sponge City initiative were assessed by the lead author. The evaluation drew on participants’ keyword selections, interview transcript analysis, and contextual interpretation. This process incorporated each interviewee’s background, professional experiences, publications referenced, and projects discussed during the interviews and associated office or site visits. Attitudes were then classified using a five-point scale ranging from 1 (highly negative), 2 (negative), 3 (neutral), 4 (positive), to 5 (highly positive).

The general attitudes toward the “Sponge City” initiative revealed distinct patterns in three cities (See Figure 6). While opinions in Shanghai were relatively uniformly positive, perspectives in Beijing and Shenzhen were more varied, ranging from highly positive to highly negative.

In Beijing, most participants had a generally positive attitude toward the “Sponge City” initiative, with 60% positive or highly positive. The negative views were like those in Shenzhen at 30%, but there were fewer neutral ones. In Shenzhen, the attitude was also generally positive, with 50% of participants being positive or highly positive. However, more people replied neutrally, with a balanced mix of positive, negative, or neutral thoughts, rather than leaning substantially toward either a positive or negative viewpoint.

In Shanghai, most interviewees had positive or neutral attitudes. The distribution has four categories: highly positive (1), positive (5), neutral (3), and negative (1). This trend suggests considerable support for the “Sponge City” policy and implementation. The absence of a highly negative attitude indicates that the “Sponge City” initiative was generally well received by most practitioners in the study sample. The greater percentage of neutral attitudes (30%) among Shanghai participants might suggest a more cautious or wait-and-see approach among some practitioners and experts.

By combining the data from Beijing, Shanghai, and Shenzhen, the following overall attitude distribution was generated (Figure 7 and

Table 2. Overall attitudes toward “Sponge City” and the number of participants in each category.

Highly Negative	Negative	Neutral	Positive	Highly Positive
4	3	6	11	6

), showing a diversity of practitioner opinions with a positive main trend.

Overall, practitioner attitudes toward the Sponge City initiative were generally positive. Most participants expressed positive or highly positive views, indicating broad acceptance and support within the field. However, the presence of negative and highly negative responses, particularly in Shenzhen and Beijing, highlighted specific concerns that warranted attention. A notable share of neutral opinions also suggested that some experts remained cautious or believed that further evidence and evaluation were needed. These reservations likely reflected differing levels of awareness, experience, and perceived feasibility, as well as city-specific challenges in planning and implementation.

The greater diversity of perspectives in Beijing and Shenzhen reveals a more complex and nuanced understanding of the initiative. This variation underscores both the recognized benefits and the challenges that must be addressed to strengthen the success and long-term viability of Sponge City projects.

Interestingly, a brief sub-analysis by participants’ years of experience shows notable differences in views on long-term Sponge City viability. The eight participants with 30+ years of experience expressed the widest range of opinions, from the strongest support to the most critical assessments, including the view that the initiative has “basically failed”. Several in this group were retired or nearing retirement, giving them more freedom to speak candidly. In contrast, those with 5–10 years of experience tended to offer more cautious and consistent evaluations aligned with government policy. This divergence suggests that career stage may influence technical evaluations and professional perspectives.

3.2. RQ2: How Did Climate Change Considerations Influence the Planning and Design of Sponge Cities, and What Strategies Were Employed to Enhance Their Viability?

Climate change planning is typically categorized into adaptation and mitigation. Adaptation involves measures to manage the effects of anticipated climate change, while mitigation focuses on reducing greenhouse gas emissions to lessen the necessity for adaptation [42]. Insights on this topic were gained from responses to the interview question: “Did climate change factor in your Sponge City planning and design? If yes, what were your strategies to deal with it?” The results showed a strong emphasis on climate change adaptation among participants, with responses nearly identical across the three cities. In Beijing and Shanghai, 90% of practitioners prioritized adaptation, compared with 80% in Shenzhen.

3.2.1. Common Themes in Climate Adaptation

Based on climate change-related responses from 30 interviewees in Beijing, Shanghai, and Shenzhen, several key themes emerged, revealing both consensus and divergent perspectives in adaptation strategies across the three cities (Figure 8).

• Adaptation Capacity to Extreme Weather Events

Adaptation to extreme weather events is a controversial topic. While many participants viewed the Sponge City approach as a vital strategy for enhancing climate resilience, others expressed skepticism, questioning whether the sponge system could truly withstand the scale and intensity of extreme weather events.

• Supportive Views

Supporters emphasized the importance of planning for extreme weather, updating stormwater formulas, and incorporating resilient measures in Sponge City planning and design. Their strategies included reserving land for water retention, creating multifunctional floodable spaces, updating stormwater formulas and standards, using climate models to project future rainfall and flood risks, strengthening flood-warning systems, and deploying site-specific interventions. They also emphasized the broader goal of developing an integrated urban water-safety framework capable of managing diverse climate impacts.

• Skeptical Views

Over one-third of participants expressed skepticism, noting that the Sponge City approach was not effective in managing extreme weather events. They emphasized its limitations and challenges in addressing severe conditions. Below are representative quotes from interviewees in three cities.

Beijing: “Using historical weather data to predict future extreme weather events is difficult. Sponge Cities may not handle 100-year events effectively” (BJ3). “Sponge Cities are mainly designed to handle frequent light rainfall events or moderate rainfall events currently. It cannot handle extreme heavy rainfall events that are rare but have a low probability of occurring” (BJ6).

Shanghai: “In extreme situations like typhoons, rain gardens alone cannot handle the stormwater. We need additional measures, but accurate calculations for future scenarios are difficult due to varying climate change data” (SH2). “‘Sponge City’ measures are more of an ‘icing on the cake’ rather than a fundamental solution. They help reduce pressure on municipal drainage systems but are not designed to handle extreme weather events effectively” (SH7).

Shenzhen: “I think extreme situations vary by project. ‘Sponge Cities’ can handle rainfall of about 30 mm in Shenzhen, but in extreme weather with rainfall over 100 mm or like Zhengzhou’s 600 mm in a day, the impact of Sponge Cities is very minimal” (SZ2). “I believe that Sponge Cities cannot cope with extreme weather. They are unable to handle severe flooding or extreme drought, but they can help mitigate the impacts” (SZ4). “I believe the only solution to extreme weather events now is large-scale municipal engineering projects, like those in Japan” (SZ8).

The debate underscores differing views on the viability of Sponge City for managing extreme weather. Some saw it as vital for urban resilience, while others argued it failed under severe conditions. Skeptics argued that only large-scale sponge measures can manage stormwater during extreme events, as smaller facilities often handle only light rain, and sometimes fail even in moderate conditions.

2.

Climate Considerations in Urban Planning

Integrating climate change considerations into urban planning emerged as a common theme. Participants stressed the importance of cross-disciplinary approaches and the incorporation of climate factors into Sponge City planning. Several pointed out that effective implementation required coordinated efforts at a larger, watershed-scale with “giant sponges”, enabling integrated “Sponge City” regions and positioning stormwater management as a vital aspect of urban planning.

3.

Nature-Based Solutions

Nature-based solutions (NBS) were widely cited by participants, though interpreted in notably different ways. Many interviewees emphasized their importance but also observed that the current Sponge City approach in China relies heavily on green or “soft” measures and lacks effective integration with engineered, gray infrastructure. At one extreme, an expert advocated systematically removing dams and concrete riverbanks to reestablish natural flooding defenses. Others were more skeptical of NBS, describing smaller interventions like rain gardens, often referred to as “mini sponges”, functioning more as aesthetic or supplementary enhancements with limited impact on flood control and urban resilience (SH7). These perspectives reveal variation in how practitioners and experts understand the role and function of NBS.

4.

Smart Water Technologies and Data

Innovative technologies and tools that use sensors, analytics, and real-time data to manage urban water efficiently and sustainably were widely emphasized by participants. They highlighted the significance of smart monitoring systems for stormwater management, real-time weather data for flood risk assessment, and updating rainfall intensity formulas based on current data. Additionally, participants noted that technology is transforming education by fostering interdisciplinary knowledge and collaboration.

5.

Cost-effective Practices

Several participants advocated for practical, low-cost approaches in climate-sensitive planning and practice. They suggested converting low-lying park areas into rain gardens or adding small, dispersed ponds in natural valleys as effective and economical options. These open drainage systems not only store water but also help regulate local climates. In contrast, expensive interventions, such as underground storage tanks beneath commercial buildings, were criticized for high costs, limited capacity, and minimal environmental benefits. A broader, watershed-based approach tailored to local conditions was recommended to maximize effects while minimizing costs.

3.2.2. Climate Change Mitigation

Climate change mitigation efforts involve actions to reduce or prevent greenhouse gas emissions, including shifting to renewable energy, enhancing energy efficiency, and adopting practices like protecting forests [43]. Four out of 30 participants adopted and shared climate mitigation measures, while one expert addressed challenges in incorporating climate mitigation strategies through design alone. Below are quotes from those individuals who took climate mitigation into consideration. Their emphasis differed based on their professional backgrounds and experiences.

• “Climate change factors are considered throughout the entire process according to the carbon principles. Design must be integrated with nature” (BJ5).
• “Mitigating climate change must go beyond a carbon-centric approach, considering broader ecological impacts, promoting biodiversity, and enhancing system resilience” (BJ8).
• “We strive to use green energy and natural materials as much as possible in all designs” (SH3).
• “We engage in low-carbon city planning and set requirements for urban low-carbon and green development indicators” (SZ1).
• “I think it’s difficult to change things like carbon emissions and the urban heat island effect through design alone. These are more about establishing values, environmental education, and adjusting our living style, which are hard to change from the bottom up through design. To address climate change challenges through design, we should focus on solving our water issues through planning, as I believe water is at the core of all our problems” (SZ5).

While a few participants brought up mitigation strategies, these conversations were far less frequent than those centered on climate adaptation. This reflects the current policy and practitioner perspectives in China, where the implementation of Sponge City is primarily framed as a mandate for storm runoff control and flood risk management rather than a more comprehensive approach to climate mitigation, because the benefits of mitigation are generally viewed as indirect, long-term, and difficult to measure. Furthermore, because the Sponge City effort is grounded in national stormwater management policy rather than climate-carbon policy, local agencies typically allocate resources in ways that give mitigation much less emphasis in day-to-day practice. This suggests that incorporating mitigation into Sponge City planning may require integrated national policies, revised evaluation standards, and strengthened professional and public awareness.

In summary, the strong emphasis on climate adaptation among practitioners in all three cities reflects a shared recognition of the urgent need to build climate-resilient cities across China. Recommended strategies include large-scale green-blue corridor planning, multifunctional floodable space design, updating rainfall intensity formulas, strengthening flood risk warning systems, and implementing site-specific green infrastructure. Aligning Sponge City projects with these adaptation strategies will enhance their capacity to manage intensified climate impacts, improving current and long-term effectiveness and viability.

3.3. RQ3: What Are the Perceived Opportunities and Challenges Affecting Sponge City’s Viability Across Different Dimensions of the Conceptual Framework?

This section focuses on analyzing responses to the interview question: “What opportunities and challenges may affect ‘Sponge City’ viability across the six dimensions of the conceptual framework?” The goal was to identify perceived opportunities and obstacles influencing Sponge City development, provide insights to strengthen urban resilience, and capture lessons learned throughout the process. The analysis was guided by the conceptual framework introduced in Section 1.1 to assess Sponge City viability across six dimensions: environment, economy, governance, urban form, civic engagement, and human wellbeing. The conceptual framework diagram (Section 1.1, Figure 1) was shown to each participant during the interview process. The following summarizes key themes of challenges and opportunities across the six dimensions, with representative quotes.

3.3.1. The Governance Dimension

Governance plays a crucial role in social sustainability, entailing the ability of the society to put policies into place to ensure respect for human rights, diversity, cultural traditions, and community rights [44]. Effective and sustainable governance is essential for Sponge City viability. Among the six dimensions in the proposed framework, governance was considered the most critical by six participants across three cities, and its importance was cited more frequently than that of any other dimension. Figure 9 and Figure 10 illustrate the key themes of governance-related challenges and opportunities influencing Sponge City viability, along with their respective frequencies of mention.

• Key Themes in Governance Challenges Affecting Sponge City Viability

• Top-down Government Control

Centralized, top-down decision-making increases the likelihood of politically motivated projects, a lack of transparency, and poor community buy-in, all of which undermine long-term viability. “In China, the will of the superiors is basically the dominant force” (BJ1). “No public involvement. The State dominates the decision-making” (SH4).

2.

Policy Unsustainability and Misguidance

Short-term mandates often result in fragmented, superficial solutions, while the absence of long-term maintenance policies renders ‘Sponge City’ projects unsustainable. Participants voiced serious concerns: “There are some misconceptions in the policy, focusing only on local site drainage, but ignoring the watershed issue” (BJ8). Another noted, “Maintenance is loose and lacking. After 3 to 5 years, facilities were simply abandoned” (SH7).

3.

Insufficient Interagency Coordination

Fragmented governance and a lack of interagency coordination reduce efficiency. “Management is challenging due to coordination demands across departments and stakeholders. Current communication and collaboration are insufficient” (SZ5).

4.

Lack of Meaningful Performance Assessment

Absence of meaningful and practical evaluation methods for assessing compliance and effectiveness is an ongoing challenge. “How strong is the function of the ‘Sponge City’ project? At present, it seems quite difficult to evaluate” (SH6).

5.

Ideological Barriers

Mindset gaps among leaders hinder progress. Not everyone has the same mental maps regarding Sponge City. As SZ10 mentioned, and five others echoed: “The biggest challenge lies in achieving ideological acceptance and understanding” (SZ10).

• Key Themes in Governance Opportunities Supporting Sponge City Viability

• Policy Support

China’s Sponge City planning and practices prioritize robust government policies, ensuring government-led initiatives for implementation. “Good policy is the determining factor; all others will follow” (BJ5).

2.

Long-term Goals and Continued Improvement

The government can set clear long-term objectives and focus on optimization and normalization of Sponge City practices over time. “The focus has shifted from feasibility to ensuring routine implementation and continuous optimization” (SH4).

3.

Government-led Outreach and Public Education

Government-led outreach and education provide great opportunities to embed Sponge City concepts into society and ensure broad public support. “Public outreach should be organized by the government and public media” (SH8).

3.3.2. The Economic Dimension

The economic dimension of Sponge City viability encompasses both the financial needs and the potential economic returns associated with implementing sustainable urban stormwater systems. Contextual considerations include cost-effectiveness, reliable funding mechanisms, and the integration of sustainable practices within broader urban development processes. Securing necessary funding for the implementation of all Sponge City projects is a considerable challenge in China [45]. Five participants across three cities identified this as a critical dimension, ranking it second in importance from a practitioner’s perspective. Figure 11 and Figure 12 illustrate the key themes of economic challenges and opportunities influencing Sponge City viability, along with their respective frequencies of mention.

• Key Themes in Economic Challenges Affecting Sponge City Viability

• High Upfront Cost and Funding Constraints

High financial demand makes Sponge City projects difficult to carry out thoroughly due to their high initial capital costs. “Funding is insufficient; financing is difficult, and many projects require large amounts of money” (SZ5).

2.

Lack of Economic Returns and Benefits

Difficulty proving economic effectiveness and Return on Investment (ROI) fuels doubts and debate. “If you look purely at economic returns, the ‘Sponge City’ isn’t a money-making business; benefits must be reflected elsewhere” (SH8).

3.

Private Sector Reluctance & Weak Market Incentives

Developers hesitate without clear incentives; market signals do not yet reward sponge features. “Beyond government, few will pay; some firms fund showcase projects mainly for branding” (SZ4).

4.

Maintenance and Lifecycle Costs

Regular maintenance is needed. With insufficient funding, maintenance lapses can lead to system failures and undermine public trust. “Without ongoing maintenance, facilities clog and become economically unsustainable” (SH1).

• Key Themes in Economic Opportunities Supporting Sponge City Viability

• Cost-Saving Potential

Sponge City practice can achieve significant cost savings in stormwater management by designing with natural landforms, using low-cost materials, low-maintenance plants, and reusing rainwater. “We can significantly reduce construction costs by using natural methods with scientific calculations, making ‘Sponge City’ more acceptable to citizens” (SH3).

2.

Increasing Marketability and Property Values

Sponge City projects may attract buyers who respect sustainability, potentially increasing marketability and property values. “People are more inclined to buy a property when it is labeled as a ‘Sponge City’ project” (BJ2).

3.

Risk Reduction as Economic Justification

Sponge City investment can be positioned as a cost-saving measure against flood damage and climate risks. “If runoff is not controlled, it can lead to flooding and huge economic losses” (SH2).

3.3.3. The Environmental Dimension

The environmental dimension was identified by participants as another key factor, ranking third in importance after governance and economy. Some thought the biggest challenge with Sponge Cities lay in the environmental aspect (SH7 and SZ3). Concerns centered on persistent urban flooding risks. Experts see that hydrological and ecological systems have collapsed, so there is no choice but to restore them. Figure 13 and Figure 14 illustrate the key themes of environmental challenges and opportunities influencing Sponge City viability, along with their respective frequencies of mention.

• Key Themes in Environmental Challenges Affecting Sponge City Viability

• Intensified Extreme Weather and Climate Change Impact

Intensified weather events and rising temperatures pose major challenges to Sponge City viability. These conditions can overwhelm nature-based systems, accelerate infrastructure wear, and demand greater adaptive capacity. As SZ3 warned: “Our current Sponge Cities have not achieved the expected goals. They have not managed to alleviate climate risk” (SZ3).

2.

Complicated “Urban Syndrome” after 40 Years of Development

Rapid urbanization has led to ecological degradation, biodiversity loss, and damaged water environment, resulting in complex urban environmental challenges that the Sponge City approach alone may not be able to fully resolve. “China’s past 40 years of development ignored nature-based design. Now trying to use ‘Sponge City’ to solve urban flooding problems in big cities is simply absurd” (SZ8).

3.

Systemic Water Problems

China faces interconnected water challenges, such as floods, water scarcity, rainwater uneven distribution, and pollution, often worsened with short-term, gray infrastructure solutions. “Water is at the core of all problems—hurricanes, floods, and even sea-level rise are interconnected” (SZ5).

4.

Disservice with Negative Environmental Impact by Sponge City Construction

Poorly planned and built Sponge City projects can create unintended consequences, such as mosquito breeding, foul water, material pollution, and accessibility issues. As noted by BJ10: “Rain gardens often lead to increased mosquitoes and foul water” (BJ10).

• Key Themes in Environmental Opportunities Supporting Sponge City Viability

• Enhancing Climate Resilience

The Sponge City approach aims to adapt to climate change, reducing vulnerability to extreme weather and enhancing climate resilience. “This opportunity is deeply connected to environmental and climate change issues, which I believe will resonate strongly with people. I need Sponge City!” (SZ7).

2.

Offering Ecosystem Services and Environmental Benefits

The Sponge City initiative can provide multifunctional benefits, such as biodiversity enhancement, habitat creation, water purification, and improved microclimate, contributing to ecological health and urban sustainability. “The goal is to restore the ecosystem with water as the dominant factor and improve its comprehensive ecosystem services” (BJ8).

3.

Solving Systemic Water Problems Holistically

Sponge cities address flooding, drought, and water quality issues comprehensively through nature-based solutions. As BJ8 stated: “Sponge City opens a new journey to comprehensively solve prominent water problems in Chinese cities” (BJ8).

4.

Treating “Urban Syndrome” with Nature-Based Solutions

Restoring natural processes and urban greening can counteract urban ecological degradation and help heal “Urban Syndrome”. “Sponge City can address ‘Urban Syndrome’ by systematically improving flood resilience, water ecology, and overall quality of human living through integrated, citywide interventions” (SZ10).

3.3.4. The Urban Form Dimension

Urban form was acknowledged by some participants as a crucial dimension to assess Sponge City viability in China (BJ3 SZ6). While some experts suggest that urban form is relatively easy to handle (BJ4), others emphasize the difficulty of incorporating sponge measures into high-density cities such as Beijing (BJ2, BJ6) or adjusting to varied regional situations (SH1, SZ3). Many people feel that urban form should extend beyond physical design to incorporate ecological planning (BJ8, BJ9), adaptable architecture (SZ1), and long-term maintenance (SZ10). SZ8 recommends that urban form should be rooted in local context and landscape, whereas BJ8 emphasizes the need for systemic, nature-based solutions to address urban flooding problems under climate change. Figure 15 and Figure 16 illustrate the key themes of urban form-related challenges and opportunities influencing Sponge City viability, along with their respective frequencies of mention.

• Key Themes in Urban Form Challenges Affecting Sponge City Viability

• Repercussions of Inadequate Planning and Design

Rapid urbanization, coupled with inadequate urban planning and design, has destroyed the natural environment and disrupted hydrologic processes. This transformation has resulted in extensive impervious surfaces and the loss of floodplains, conditions that cannot be fully remedied by the ‘Sponge City’ initiative. As experts emphasize: “The land that has been damaged requires a long period of restoration” (SZ4) and “The damage can no longer be fixed simply by applying ecological methods; it is beyond correction in that way” (SZ8).

2.

Scale Mismatch with Fragmented Approaches

Sponge City efforts are fragmented, focusing on small-scale LID features without city-scale and watershed integration, limiting cumulative benefits. “There is the ‘sponge’ form, but it doesn’t solve real stormwater problems. The focus is on small pilot areas” (BJ1). “We call it sponge fragmentation… Many micro projects, but the overall effect is weak” (SZ1).

3.

Rigid, One-Size-Fits-All Design Standards

Current design standards impose rigid, one-size-fits-all indicators over flexible, practical solutions, resulting in surface-level compliance without solving real urban stormwater issues. “Applying a single national standard often results in rigid compliance and waste, or inappropriate solutions. For example, many northern cities with little rainfall find permeable pavements unnecessary and costly” (SH7).

4.

Lack of Post-Construction Maintenance

Post-construction maintenance is often overlooked, leaving gaps in the long-term functionality of Sponge City features. Without sustained upkeep, nature-based systems degrade and fail to deliver intended benefits. “In Shenzhen, many of those sponge infiltration systems became clogged over time, and maintenance couldn’t keep up afterward” (SZ9).

5.

Urban Density and Other Physical Constraints

Dense urban morphology and historical encroachment on natural systems disconnect surface and subsurface flows. Outdated underground engineering networks constrain hydrologic restoration. “A very important issue is land availability in ‘Sponge City’ projects. Many places want to build Sponge Cities, but very little land limits them” (BJ3).

6.

Technical Incompetence and Material Quality Concerns

Sponge City projects may fail to achieve their comprehensive goals due to technical incompetence across the design and construction phases. Low material quality reduces infiltration and durability, making systems ineffective over time. “Depressions in the landscape can have a negative impact on plants and even lead to mosquito proliferation. It is ultimately a technical issue, stemming from inadequate design and implementation” (SH9).

• Key Themes in Urban Form Opportunities Supporting Sponge City Viability

• Systemic Thinking and Multidisciplinary Urban Planning

Integrated, forward-thinking, and multidisciplinary planning can combine ecological principles with stormwater management to build resilient urban systems. “Cross-disciplinary collaboration is very important. For example, hydrologists should engage in joint discussions and research with experts in ecology and botany to achieve integrated solutions” (SH7).

2.

Multi-Scale Integration against Fragmentation

Opportunities to link watershed-scale planning with district- and site-level design and integration of blue-green-gray infrastructure can deliver cumulative benefits and prevent fragmented interventions. As BJ8 noted: “Sponge Cities start a new journey to comprehensively solve water and environmental issues at multiple scales with nature-based solutions” (BJ8).

3.

Adaptive, Context-Specific Design

China’s Sponge City initiative can tailor planning and design to local conditions while enhancing climate resilience with adaptive design, such as floodable parks. “Sponge City implementation should align with local realities to be effective” (SH10).

4.

Integrating O&M into Design and Implementation

Embedding long-term Operations and Maintenance (O&M) strategies into design ensures sustained Sponge City performance and resilience. “Effectiveness depends on ongoing operations and maintenance. Without it, benefits cannot be achieved” (SZ10).

3.3.5. The Civic Engagement Dimension

Many participants believed that civic engagement was critical in China’s Sponge City initiative. Opinions varied on the extent of public involvement. Some felt that community participation had been relatively strong in cities like Beijing and Shenzhen, while others thought it remained limited across most of China, with a few even suggesting it was virtually nonexistent. While some linked civic engagement to governance or cultural norms, many saw civic engagement and human wellbeing as closely connected and potentially unified into one dimension. As SZ5 noted, civic engagement was the starting point and human wellbeing the ultimate goal. Figure 17 and Figure 18 show the key themes of civic engagement-related challenges and opportunities influencing Sponge City viability, along with their respective frequencies of mention.

• Key Themes in Civic Engagement Challenges Affecting Sponge City Viability

• Top-Down Decision-Making with Limited Public Participation

Sponge City practice in China is largely driven by government authority and top-down decision-making, leaving limited space for community involvement in planning and design. “Currently, there is no public participation. It’s all executed under state directives” (SH4-6).

2.

Lack of Public Awareness and Environmental Education

Lack of awareness of the Sponge City concept and climate adaptation reduces public involvement and support. “Environmental education is lacking. People prioritize development and personal interests over caring for the environment” (SZ5).

3.

Communication Issues and Outreach Gaps

Limited outreach and ineffective communication hinder stakeholder engagement. Interaction and transparency at the grassroots level are lacking. “Public participation is rare, mostly small stakeholder meetings, few large public venues” (SH2).

4.

Challenge in Cultural and Behavioral Change

Building a culture of participation and environmental stewardship requires systemic promotion for behavioral shifts, which remain underdeveloped. As SZ8 noted: “Citizen participation should become a cultural condition… It needs to turn into a habit embedded in everyday behavior” (SZ8).

• Key Themes in Civic Engagement Opportunities Supporting Sponge City Viability

• Promoting Participatory Mechanisms

Strengthening channels for citizen input, such as project disclosure and hotlines can enhance transparency and responsiveness in Sponge City projects. As BJ7 shared: “Our projects now include public participation. Citizens can call the 12345 hotline, and authorities must respond within set timeframes” (BJ7).

2.

Enhance Public Education and Awareness

Increasing environmental literacy through schools, media, and interactive activities can build understanding of Sponge City benefits and limits, supporting long-term engagement. As BJ2 noted: “We run ‘Sponge City’ programs in schools and communities. PhD students teach in primary schools, and media campaigns raise awareness” (BJ2).

3.

Policy Support and Incentive Structures

Government incentives and supportive policies can boost community participation and shared responsibility, easing financial burdens and improving sustainability. “Government provides funding and guidance for shared Sponge City rain gardens. Residents co-create with official support” (SZ2).

4.

Community-Led Co-Creation and Contextual Design

Engaging residents in design processes can ensure solutions reflect local needs and cultural context, improving acceptance and functionality. “Citizen participation should become a cultural norm embedded in everyday behavior” (SZ8).

3.3.6. The Human Wellbeing Dimension

Wellbeing is defined as “the state of feeling healthy and happy” [46]. The Sponge City initiative aims to promote human wellbeing, as listed in the 2021 “Systematic & Comprehensive ‘Sponge City’ Promotion Policy Outline” [47]. However, in the current practice, experts noted that technical priorities often overshadowed human-centered goals, poor design diminished public experience, and limited environmental awareness weakened feedback loops. Still, opportunities exist. Well-designed spaces can support mental health and emotional connection. Multifunctional environments can benefit both people and nature. When rivers are clean and green infrastructure thrives, human and nature coexist harmoniously, a vision central to Sponge City viability. Figure 19 and Figure 20 display the key themes of human wellbeing-related challenges and opportunities influencing Sponge City viability, along with their respective frequencies of mention.

• Key Themes in Human Wellbeing Challenges Affecting Sponge City Viability

• Persistent Flood Risk and Public Safety Issues

Many Sponge City projects fail to meet the targeted goals of mitigating flood risk and safeguarding human wellbeing. Severe urban flooding and damage continue to occur, undermining public trust and safety. Technical measures alone cannot guarantee resilience, and poor maintenance or design can even create health hazards such as mosquito breeding and water pollution. “The publicity exaggerated its role in preventing urban flooding, but after heavy rain, cities were still submerged. People were very dissatisfied… In many parts of Shenzhen, sponge infiltration systems became clogged over time, and maintenance couldn’t keep up, leading to mosquito infestations and the spread of disease” (SZ9).

2.

Poor Human Experience and User Discomfort

Sponge City projects frequently neglect user comfort, cultural memory, accessibility, and experiential quality. Lack of human-centered design limits systemic benefits and public acceptance. As SZ10 noted: “In site plans, pits appear everywhere, especially in residential complexes. People say that these areas should consider activities for the elderly and children. With so many pits, they see them as pointless and resist” (SZ10).

3.

Unhappiness due to Value Misalignment and Lack of Environmental Awareness

Public education and awareness remain low. This leads to skepticism and dissatisfaction toward Sponge City interventions. “What ‘Sponge City’ development in China lacks most is environmental awareness, rooted in weak environmental education” (SZ5).

• Key Themes in Human Wellbeing Opportunities Supporting Sponge City Viability

• Enhancing Climate Resilience to Safeguard Human Wellbeing

Intensified climate change impact highlights the critical need for enhanced safety and resilience measures in Sponge City planning, essential for safeguarding human wellbeing. As SZ5 noted: “Sponge City aims to improve people’s livelihoods. It is also intended for disaster relief” (SZ5).

2.

Multifunctionality Promoting Mental and Physical Health

Sponge City projects can promote mental and physical health, recreation, and active lifestyles. Multifunctionality ensures ecological benefits while improving the quality of life. “Small rain not soaking shoes makes people feel good… Flowers and greenery create an aesthetic experience” (SZ6).

3.

Fostering Understanding through Awareness

Building awareness can foster shared responsibility, improve public perception, and ensure long-term Sponge City viability. “We need to tell the public that many times you cannot fight against nature. We must respect it, learn to respond to emergencies, and learn how to avoid risks” (SZ1).

4.

Promoting Cultural Enrichment and Community Pride

Sponge City can create memorable places that become destinations and enhance community pride, fostering cultural identity and social interaction. “I think it’s about culture and deep-rooted memory, allowing people in big cities to understand and experience how crops grow, and showing this to urban children” (SH3).

4. Discussion

This section of the study is organized around the six dimensions outlined in the proposed conceptual framework. Results of 30 first-hand interviews were compared with insights from five WoS-indexed articles listed in the Literature Review [14,27,28,29,30]. This section also compares interview insights with fieldwork observations. Overall, the integrated research findings provide more granular, practice-based insights into how the challenges and opportunities manifest in Sponge City planning and practice in China.

4.1. Interview Findings Compared with Literature in Six Dimensions

4.1.1. Governance

In this study, governance emerged as the most critical factor, acting both as a constraint and an enabler of “Sponge City” viability. Interviews repeatedly revealed systemic challenges: centralized, top-down decision-making limits transparency and public participation; short-term mandates and insufficient interagency coordination lead to fragmented, ineffective solutions; and the absence of an operations and maintenance (O&M) policy and effective performance evaluation system undermines long-term functionality. These findings align with Li et al. [14], Hawken et al. [27] and She et al. [28], who highlight weak institutional frameworks and a lack of evaluation standards and maintenance management. Practitioners also noted political pressures to meet evaluation targets, which in some cases led to projects being pursued more for compliance than for substantive impact. This dynamic is exemplified by SZ9’s comment about “building a Sponge City for the sake of Sponge City evaluation” and is consistent with criticisms in the literature that describe the concept as a policy “slogan” [25]. Yet, interviewees also identified strong policy support, government-led outreach, and the potential for long-term goal setting and normalization to embed Sponge City practices into routine urban management. Previous studies reinforce these prospects generally. Both interviews and literature converge on the need for whole-process management, clear responsibilities, and normalized O&M practices to ensure sustainability beyond initial construction.

4.1.2. Economy

Several interviewees identified the economic dimension as the second most significant challenge. Notably, none of the reviewed studies highlight this ranking. Economic factors present persistent challenges but also opportunities for Sponge City viability. Interviews underscored high upfront costs, insufficient funding for lifecycle maintenance, and difficulty demonstrating economic returns: “Funding is insufficient; financing is difficult” (SZ5) and “We have investment figures, but no data on benefits” (BJ1). Private sector reluctance and lack of stormwater fees exacerbate these issues, leaving O&M underfunded. Previous studies confirm these concerns: Li et al. [14] and Hawken et al. [27] note economic dimensions underperform in China, while Zhang et al. [30] conducted a comprehensive study identifying critical PPP risk factors through expert assessments. Conversely, our interviewees highlighted more cost-saving opportunities through nature-based solutions and risk reduction as economic justification. Both sources converge on the need for innovative financing, such as stormwater utility fees and PPP reforms, to ensure long-term viability beyond initial construction.

4.1.3. Environment

Environmental considerations emerged as a critical dimension in both interviews and literature as environmental factors pose significant hurdles but also offer opportunities for Sponge City viability. Interviews emphasized that intensified climate change and extreme storms are overwhelming designs focused on small rainfall events, while decades of rapid urbanization have compounded systemic water challenges: “We are paying the price for the reckless development of the past 40 years, the trampling of nature and disruption of ecological systems. The damage can no longer be corrected simply by applying ecological methods. It’s beyond correction in that way” (SZ8). Sponge City projects can also create disservices such as mosquito breeding and foul water. Practitioners stressed that current Sponge City practices often adopt a one-size-fits-all approach, ignoring diverse climates, soils, and hydrological contexts across China. Previous studies echo these concerns and call for context-specific objectives [14] and flood disaster risk management [28]. Opportunities identified by both sources converge on embedding nature-based solutions tailored to local conditions, restoring ecosystems, and delivering co-benefits such as cooling and biodiversity.

4.1.4. Urban Form

Urban form was recognized as a decisive factor shaping Sponge City outcomes. Interviews exposed major challenges, particularly due to rapid urbanization and reckless design practices that disturbed natural hydrologic systems, leading to widespread impervious surfaces and the loss of floodplains. “Following 30 to 40 years of rapid development, Chinese cities have suffered from numerous ‘urban ailments’, particularly in the water environment. The water quality of urban river systems was far from ideal; in fact, one could often detect a distinct odor rising from the riverbanks in the heart of the city” (SZ10). They also noted rigid, one-size-fits-all design standards, scale mismatches, and a shortage of professionals capable of delivering integrated, context-specific solutions. In contrast, the five reviewed studies touch on these issues only broadly, emphasizing integrated planning and adaptive design [14,27,28]. Both sources recognized opportunities with systemic thinking, such as combining watershed-scale planning with site-level interventions, integrating blue-green-gray infrastructure and incorporating O&M measures to achieve long-term performance. Interviews greatly enriched this dimension by providing specific project details and addressing gaps in the literature, which remains largely conceptual.

4.1.5. Civic Engagement

Civic engagement has remained a weak area in China’s Sponge City practice. Interviews revealed top-down decision-making hindered public participation: “there is currently no public participation. It’s all executed under state directives” (SH6). They also mentioned a lack of environmental awareness and out-of-date outreach strategies, which diminished community support. The literature confirms these inadequacies, highlighting that participatory procedures are weak in China [14,27]. The level of participation was also greatly affected by Sponge City project type and location [29]. Both sources noted opportunities for developing participatory channels, improving environmental education, and encouraging co-creation to connect design with local requirements. Interviews added depth to this subject by identifying cultural and behavioral limitations, as well as the necessity for interactive, context-sensitive engagement strategies, as noted by SZ8: “Citizen participation should become a cultural norm embedded in everyday behavior.”

4.1.6. Human Wellbeing

The Human wellbeing dimension exposed persistent gaps in Sponge City planning and practice. Interviews highlighted those projects that failed to satisfy flood-risk reduction objectives while ignoring user comfort, cultural memory, and accessibility: “Whenever urban flooding occurs, people say ‘Sponge City’ was built for nothing” (BJ6). Poorly planned and implemented projects also posed health risks, exacerbating public dissatisfaction. Moreover, several practitioners emphasized that current Sponge City systems are not designed to reliably manage 100-year extreme rainfall events, underscoring the need for transparent communication to the public about technical limits. The literature supports these concerns and cautions against overpromising Sponge City’s ability to manage extreme floods [14,27,28]. Both sources converge on opportunities to enhance multifunctionality by delivering social and environmental benefits such as mental and physical health, cultural enrichment, and stormwater management. Interviews provide more in-depth, empirical insights, emphasizing the importance of implementing human-centered design principles and bridging gaps in the literature that lacks specifics on addressing human well-being from the experts’ perspective.

Although “Civic Engagement” and “Human Wellbeing” are listed as two distinct dimensions within the framework in Section 1.1, the interview findings reveal a strong interconnection between them. Civic engagement influences citizens’ understanding, experience, and reaction to the Sponge City initiative, while human wellbeing reflects the societal outcomes of those actions. Several interview findings highlight the overlap and show how meaningful participation can affect public knowledge, trust, and everyday experiences living in the Sponge Cities. Therefore, these two dimensions are viewed as analytically distinct but conceptually connected, capturing both the processes of community engagement and the broad wellbeing implications that support long-term viability.

4.1.7. Time Horizon of Viability

The research results also pointed to suggestions to broaden the dimensions of Sponge City. Two interviewees proposed adding Time as an additional dimension (BJ5 and BJ7). Multiple participants argued that Sponge City is a long-term endeavor. “Damaged land requires a long period of restoration. Once our green mountains and clear waters are destroyed, the cost of repairing them becomes significantly higher” (SZ4). The literature confirms that, as Li et al. [14] point out: “Sponge City approach often demands more time and different performance milestones than traditional approaches” [14]. Building green solutions for modern cities takes time for professional training, public education, and incremental learning [14]. Viability should be assessed across evolving policy, market, and social dynamics.

4.2. Fieldwork Observations Compared with Interview Findings

Field studies conducted in July 2024 revealed notable environmental benefits, such as improved stormwater retention, microclimate cooling, and increased biodiversity. Social benefits included expanded recreational spaces for all ages in Beijing Olympic Forest Park and Shanghai Xuhui Runway Park, as well as enhanced coastal resilience and multifunctionality in Shenzhen’s East Dike. However, substantial issues were evident: inadequate maintenance in public open spaces and residential districts, and in some cases, developers altered newly built sponge facilities, compromising the original design intent. For instance, in a Shanghai park, a malfunctioning water filtration system caused by overgrown aquatic plants resulted in poor water quality, raising concerns about long-term functionality.

These findings align closely with interview insights, which also emphasized environmental and social gains while warning of systemic weaknesses in maintenance and management. Both sources underscore the need for robust operations and maintenance frameworks, clear accountability, and stronger policy enforcement beyond initial construction for long-term functionality.

4.3. Scale and Feasibility

Scale and feasibility are other issues. China’s national goal of retaining 70% of rainwater onsite for 80% of built urban areas by 2030 [19] sets an ambitious benchmark. Experts did not reach a consensus on whether this goal was achievable. Some said there was no goal that could not be achieved in China (SH4-6), while others stated that this was a significant challenge (BJ1, SZ8, SZ10). Interviews found that citywide intervention is difficult due to fragmentation, limited land, and technical constraints. Localized initiatives have shown potential to fulfill national goals since “Sponge City” measures are now required for all new projects. However, systemic reforms are needed, such as establishing a whole-process management system, integrating multiscale, multifunctional planning and design, engaging the public, and accelerating professional training. Without these efforts, the Sponge City effort risks remaining a patchwork of pilot projects rather than a transformative and viable urban stormwater management plan in action.

4.4. Disciplinary Positionality

Positionality refers to how an individual’s social identity (race, gender, age, etc.) and life experiences can influence their worldviews and knowledge. The way we perceive the world is shaped by who we are ref. [48]. Positionality can influence research design and interpretation. This study is no exception. Disciplinary positionality means how specific professional training, institutional context, and knowledge base of a field can shape individuals’ viewpoints and judgment, besides their personal identity. In this study, the 30 interviewees’ disciplinary positionality played a significant role in shaping their perspectives. How the participants perceived Sponge City viability was influenced by their diverse professional experiences, disciplinary backgrounds, and training histories. Notably, four interviewees were trained in North America and had worked at U.S. or European firms, which influenced their mindset for interdisciplinary collaboration, design standards, and project expectations. Others were trained and practiced solely in China, resulting in different understandings and approaches. These differing perspectives led to perceived disciplinary hierarchies and introduced biases. For example, during an interview in Shenzhen, a hydrologist criticized landscape architects in general, claiming their designs were merely “ornamental” and inadequate for flood risk control. This perspective was based on subjective professional judgment rather than measurable outcomes.

4.5. Limitations

Several limitations should be acknowledged in this study. First, the Sponge City model is fundamentally a national policy framework and practice in China rather than a distinctly new stormwater management approach across the world. The findings reflect how practitioners and experts understand and implement this policy within China’s specific governance, planning, and cultural context, rather than capturing international perspectives on its broader applicability. Second, while Beijing, Shanghai, and Shenzhen provide diverse metropolitan environments, focusing solely on these three cities does not capture the full range of conditions across China’s many other urban regions, particularly secondary and tertiary cities, where geoclimatic conditions, administrative capacities, resource availability, and construction management practices may differ substantially.

Methodological constraints also shape the interpretation of results. Conducting 30 interviews was time-intensive and required strict adherence to IRB protocols, given political and cultural sensitivities in China. The dynamic political context may have shaped responses, and language translation issues could have affected nuance. Accessing qualified participants posed logistical challenges. The sample may not fully represent diverse perspectives in Beijing, Shanghai, and Shenzhen. Reliance on qualitative data introduces subjectivity despite triangulation with field studies. Acknowledging researcher influence is essential for transparency. Despite these limitations, the study offers valuable insights into Sponge City viability, filling gaps in the literature with practical evidence.

5. Conclusions

In the face of intensified flooding driven by climate change, it is legitimate to question whether the Sponge City initiative and other water-sensitive design approaches can effectively support climate adaptation [49]. This study draws on expert and practitioner perspectives to examine Sponge City viability with a proposed conceptual framework spanning six dimensions: governance, economy, environment, urban form, civic engagement, and human wellbeing, underscoring their complexity and interconnections.

The research findings reveal that while the Sponge City concept offers significant potential for holistic urban stormwater management and climate resilience, its success depends on overcoming systemic challenges. Experts highlighted rigid national standards, fragmented planning, funding gaps, and a lack of holistic stormwater management as critical barriers, alongside practitioner shortages and technical constraints that undermine long-term viability. Interviews also exposed issues in public involvement and cultural acceptance, as well as misaligned public expectations in flood protection and the lack of human-centered design. Despite these obstacles, experts and practitioners identified opportunities for multiscale, multifunctional, and context-specific planning and design, integrating blue-green-gray infrastructure and establishing robust performance and maintenance mechanisms. Inclusive policy, community participation, and public education are all essential to promote behavioral change and shared responsibility.

To date, 90 pilot and demonstration Sponge Cities have been established nationwide in China since 2015 [50]. However, the long-term viability of the initiative hinges on moving beyond isolated pilots and standardized metrics toward integrated multidisciplinary strategies that encompass ecological, socioeconomic, and technical dimensions. Sponge City approaches must go beyond conventional design parameters to achieve climate resilience and long-term functionality. Given the study’s empirical findings, the current effort to date runs the risk of continuing to be a patchwork of pilot initiatives rather than a revolutionary planning model. Therefore, the potential mentioned here should be understood as conditional: by grounding future strategies in expert insights and practical realities, and by addressing the systematic challenges documented in this research, China’s Sponge City initiative has the potential to evolve into a resilient, adaptive model to confront human-induced climate change while enhancing urban livability.