Sponge City Research Articles

Research on the treatment and utilization of hydrophobic soil in sponge city construction

This paper provides a comprehensive analysis of the characteristics of hydrophobic soil, including its strong hydrophobicity, poor water retention capacity, and unstable mechanical properties. It explores treatment technologies for hydrophobic soil such as soil amendments, bioremediation techniques, and physical treatment methods. Based on these findings, the paper proposes the utilization of hydrophobic soil as permeable paving material, filling material for rain gardens and ecological retention ponds, covering layer for green roofs, and for ecological slopes and dikes. These suggestions provide theoretical support and practical guidance for the effective use of hydrophobic soil in sponge city construction.

Research on Runoff Management of Sponge Cities under Urban Expansion

Research on Runoff Management of Sponge Cities under Urban Expansion

Alleviating urban pluvial floods via dual-use water plazas orchestrated by predictive algorithms

Old urban areas, characterized by complex land use and inadequate infrastructure, exhibit high vulnerability to precipitation extremes. The integration of dual-use public infrastructure stands at the forefront of planning initiatives to enhance urban flood resilience. This study introduces a pioneering Smart Water Plaza (SWP) system, orchestrated by predictive algorithms, to mitigate pluvial floods. A high-risk old neighborhood (4.5 km2) in Changsha, China, is selected as a case for empirical analysis. Two types of SWPs—in-situ detention, and runoff-receiving units—are initially established based on spatial mapping and potential analysis. The core feature of the SWP system is a multi-horizon 2D-1D model predictive control (MPC), which directly verifies the suitability of terrain configurations and evaluates temporal efficiency. The study plots the performance curves of the SWPs under various design rainfalls and demonstrates flood dynamics using an actual torrential event. The findings indicate that SWPs’ resilience contribution index for the stormwater system ranges from 9 % to 38 %. Furthermore, SWPs covering only 5 % of the site lead to an obvious decrease in flooded areas, with reductions ranging from 46 % to 48 %. These outcomes highlight the disaster mitigation potential inherent in multifunctional public spaces for Sponge City transformation and urban renewal efforts.

Selection of low impact development technical measures in the distribution area of expansive soil: a case study of Hefei, China

Expansive soils are widely distributed around the world. They have significant characteristics of both hygroscopic expansion and water-loss shrinkage, which have caused serious damage to road paving, construction of low-rise houses, and construction of slopes along the banks of rivers. Similarly, the implementation of low impact development measures can cause considerable difficulties in the distribution area of expansive soil. The entire urban area of Hefei is situated on expansive soil. Although Hefei city has developed a sponge city plan, it has not been carried out on a large scale for implementation of low impact development technical measures. Experimental studies have shown that exposed expansive soils produce fissures that run up and down during wet and dry cycles. These fissures are extremely unfavorable to the infiltration of surface runoff formed by short-term heavy rainfall. This is also one of the reasons for short-term rainfall in Hefei city, resulting in serious flooding in low-lying areas with a poor drainage system. At the same time, initial rainfall is ineffective in cleaning up surface source pollution. Therefore, we can enhance the characteristics of expansive soil, keep the expansive soil unexposed, and maintain a certain level of humidity. These approaches can play a better role in the control of rainfall runoff and surface source pollution. The characteristics of expansive soils can be enhanced by mixing them with weathered sand, a physical improvement, to meet the technical requirements for infiltration, interception, and purification. It is recommended to carefully select low impact development measures in the distribution area of expansive soil to avoid the occurrence of wasteful investment and poor results.

Integrating topographic factors for effective urban sponge construction in mountainous regions: A case study

The construction of sponge cities in mountainous areas is crucial to achieving high-quality development in these regions. Owing to rugged terrain, significant changes in elevation, and uneven distribution of cities, the construction of sponge cities in mountainous areas faces challenges such as difficulties in clearing mountains and roads, high cost, and varying regional development requirements. However, there is currently limited research focusing on the impact of terrain on sponge city construction plans. In this study, we developed an optimal low impact development (LID) system layout method based on the annual runoff control rate. This study suggests implementing LID plans in stages to balance cost-effectiveness and enhance resilience. The optimized case1_100 scheme, which takes regional differences into account, can effectively achieve a runoff control coefficient of less than 0.25 in 98.86% of the area. Remarkably, this achievement comes at a significantly lower total cost of only 1.22 billion RMB compared to the unoptimized case2_100 scheme (which does not consider regional differences) with a cost of 3.03 billion RMB. Interestingly, the optimized case1_100 plan, selected using the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method, has an LID layout that is closely related to the surface terrain. Structural equation modeling analysis indicates that terrain affects land types, which in turn impacts the surface impermeability and runoff coefficients, ultimately influencing the corresponding LID deployment plan. The coefficients of relative elevation and slope on the final plan are determined as −0.13 and −0.77, respectively, with a high overall explanatory power of 0.84. This indicates that terrain characteristics have a significant impact on the spatial patterns and surface features of typical mountainous cities in China and the optimal LID strategy largely depends on the initial terrain conditions. This study provides valuable insights for optimizing LID construction in sponge cities, particularly in the context of new mountainous urban planning.

Sustainable Stormwater Management for Different Types of Water-Scarce Cities: Environmental Policy Effect of Sponge City Projects in China

With high-speed urbanization, ecological space is seriously shrinking, and lagging drainage facilities contradict the ecological needs of citizens. In particular, water-scarce cities are faced with frequent stormwater disasters, such as excessive accumulation of rainwater, peak runoff and water pollution, which threaten the safety of the urban water ecological environment. This paper combined the actual construction content of the sponge city project with a whole process policy evaluation framework to examine whether the projects solve these problems and to find different approaches to the results. Utilizing entropy fuzzy comprehensive evaluation provides a systematic standard for the evaluation system. The research shows that the sponge city project can achieve a good governance effect, including constructing a suitable scheme for urban hydrological characteristics, effectively improving the rainwater treatment level of different types of water-scarce cities, and alleviating the ecological contradiction of urban water environment. The stages of policy formulation, policy implementation and policy results achieve a good degree of completion. On one hand, sponge city projects transform the infrastructure at key locations, aiming at improving the rainwater interception capacity of the streets; on the other hand, restoring original natural waters improves the capacity of water conservation and forms a sustainable ecosystem between the city and nature.

Assessing the impact of rainfall on water quality in a coastal urban river utilizing the environmental fluid dynamics code

The Haihe River, flowing through Tianjin City, grapples with pollution challenges, notably high levels of nitrogen (N) and phosphorus (P) leading to eutrophication and unpleasant odors, particularly aggravated by rainfall. This study used Environmental Fluid Dynamics Code to comprehensively analyze the water environment under three scenarios: low flow year, normal flow year, and high flow year. The investigation delves into N and P concentrations, computes atmospheric deposition fluxes, and evaluates the loads and retention ratios of N and P in the urban river network of Tianjin City. Scenario analysis reveals distinct trends, with high flow years associated with elevated N and hydrodynamics levels, while low flow years exhibit contrasting patterns. Key findings include 1) wet deposition fluxes contributing 21% of NH4+-N and 9% of TP river loads, 2) continuous rainfall and runoff resulting in immediate or delayed increases in NH4+-N, TN, and TP concentrations in surface water, 3) an increase in average N:P mole ratios downstream along the Haihe River, and 4) N and P mean retention ratios were 48% and 63%, respectively. The study suggests that implementing sponge city construction and sustainable drainage systems may improve water quality by mitigating the direct discharge of rainfall runoff into the river.

Interaction between formal and informal actors in the shadow of policymaking: Case studies of community-based urban pluvial flood risk management in Pearl River Delta cities

Policymakers increasingly integrate urban pluvial flood risk management into multiple strategies, acknowledging that local contexts and the actors involved are crucial. However, the literature on the decision-making processes of community-based pluvial flood risk management sheds little light on how local formal and informal actors relate to each other. This paper contributes to filling this research gap by exploring the interdependency between local authorities and community residents from a multilevel governance perspective. Two cases, based in Pearl River Delta Cities, are analysed to explore actors' interactions locally in the Chinese Sponge City Program, a national programme for urban pluvial flood risk management. The comparative study of the two cases leads to four conclusions. First, the Sponge City Program at the local level can be viewed as multilevel governance. Second, triggered by the goal set by the national government and the local contexts, local authorities see the benefit of locally integrating the Sponge City Program into an integrated and area-specific plan, emphasizing the importance of institutional assertiveness. Third, tensions and synergies exist in the interaction process between local authorities and residents that will have to be recognized and embraced and, where necessary, converted from constraining to enabling factors. Fourth, institutional barriers still dominate locally in the Sponge City Program because of a lack of support for cross-boundary cooperation and public participation. To span these boundaries, policymakers should be more open to changing the perspective from ‘planning for people’ to ‘planning with people’.

The "sponge city" program as a system of adaptation methods to climate changes in reforming and forming the architectural environment

This article analyzes the implementation of the «Sponge city» concept in the formation and reform of the urban and architectural environment, as a comprehensive method of adaptation to the problems caused by climate change, which was caused by the global warming of our planet. In this concept, the emphasis is on the regulation of all types of water resources in the aspects of floods, swamps and inundations. One of the main reasons for accelerating the pace of global warming is rapid industrial development and urbanization. This led to increased use of resources, including water, which created major environmental risks. The problems of climate change have worsened not only due to the growth of gas emissions into the atmosphere, but also due to the rapid and unplanned urbanization of the urban environment, which was formed in the post-industrial period and reflects the greedy approach of society to the limited resources of the planet. Due to this, large-scale post-industrial processes took place in many countries of the world, which led to significant environmental problems. The urban population grew at a rapid rate, with the simultaneous construction of the necessary infrastructure, including housing, factories and roads. Such processes also took place in the People's Republic of China, due to which the issue of regulating water resources was raised in the country, and the concept of "Sponge city" was applied as an answer. On the example of several Chinese cities of Wuhan, Pingxiang and Haikou, where this concept was successfully applied, adaptation methods and complex approaches for reforming the existing urban and forming a new architectural environment were systematized. Based on them, an action algorithm for the implementation of these methods and technologies was developed as a program of communication of all large-scale levels among themselves. Applying this program, at the levels from the region to an individual building and vice versa. A self-regenerating system is formed - a "sponge city-region-ecosystem" as a complex of innovative methods of combating floods, inundation, wetlands, excess precipitation, which promotes adaptation to climate changes and ensures sustainability , safety and harmony of the environment.

Multi-Criteria GIS for Sponge City Planning with Open Data Sources in Vigo (Spain)

Multi-Criteria GIS for Sponge City Planning with Open Data Sources in Vigo (Spain)

Exploring the Utility of Sponge Cities and Rhs for Rainwater Utilization and Urban Flood Prevention

Exploring the Utility of Sponge Cities and Rhs for Rainwater Utilization and Urban Flood Prevention

A Sponge Village Flood Response Method Based on GIS and RS Analysis Formation—A Case Study of Jiangou Village

This study was conducted in response to the Beijing–Tianjin–Hebei mega heavy rainfall event at the end of July 2023, and the severely affected and representative Jiangou village in Beijing was selected as the study area. A variety of methods were used to synthesize and analyze the situation and propose an adaptive response to heavy rainfall and flooding in the village. Based on multi-source remote sensing (RS) data, a comprehensive topographic and hydrological characterization was carried out, and the precipitation before and after the disaster was analyzed; the flood inundation area was extracted using the improved normalized water body index (MNDWI) and OTSU thresholding methods, and the changes of water bodies during the flooding period were quantitatively analyzed; and an improved convolutional-neural-network-based building identification and extraction model was constructed to extract the research distribution of buildings in the area. The sponge city construction (SPCC) method was improved to obtain a method that can mitigate flood risk and adapt to villages by constructing small artificial lakes and local topographic buffers to improve the water storage and drainage capacity of villages. The study shows that these methods are innovative in flood hazard analysis and mitigation but still need further improvement in data accuracy, simulation depth, and system evaluation.

Research on the Application of New Polylactic Acid (PLA) Fiber Concrete Materials in Urban and Rural Flood Resistance

This paper aims to study and apply new polylactic acid (PLA) fiber concrete materials to improve urban and rural flood resistance, enhance flood control and drainage capabilities, and promote sponge city construction. Through the analysis of the characteristics, proportion optimization and performance of PLA fiber concrete in actual projects, it is found that the material has good mechanical properties, environmental adaptability, economy and environmental protection, and has important application prospects in urban and rural flood control and drainage. By adjusting the proportion, selecting the appropriate fiber type and addition amount, the flood resistance and drainage capacity of concrete can be improved. Combined with 3D printing technology and modern scientific and technological means, the application and development of PLA fiber concrete will be further promoted to achieve a win-win situation of continuous improvement of urban and rural flood resistance and environmental protection. With the support of relevant technologies and policies, PLA fiber concrete has broad application prospects in sponge city construction and urban and rural flood control and drainage, and will make important contributions to improving the level of urban and rural disaster prevention and mitigation.

Pollutant accumulation characteristics of substrates and mechanism of microbial action in different ecological ditches

ABSTRACT Ecological ditches serve as one of the important measures for the concentrated infiltration of stormwater in the construction process of sponge cities. Prolonged concentrated infiltration of stormwater can lead to the accumulation of pollutants and pollution risks in the substrate of ecological ditches. In this study, two different substrate ecological ditches were constructed, namely, a combined substrate ecological ditch with zeolite + ceramsite (EA), and a biological substrate ecological ditch (EB). The accumulation characteristics of pollutants and microbial mechanisms in the ecological ditches were evaluated by simulating the cumulative rainfall test for three years. Results showed that there was serious total nitrogen (TN) contamination in both EA and EB substrates, with mean values of 718.6 and 802.7 mg/kg, respectively. The average contents of potentially toxic elements (Cu, Pb, and Zn) in EA and EB substrates were higher than the background values of soil elements in China, and Cu posed considerable ecological risks to the environment. Proteobacteria was the dominant phylum and accounted for 32.85–41.33% in two ditches; the total number of denitrifying functional bacterial genera in the EB increased by 1.53% than EA, which proved that the biological substrate was more favourable for the growth of denitrifying microorganisms. The accumulation characteristics of pollutants and microbial mechanisms in the ecological ditches with different substrates above provide a reference for extending the service life of ecological ditch facilities.

Can "sponge city" pilots enhance ecological livability: Evidence from China

Can "sponge city" pilots enhance ecological livability: Evidence from China

Application of pervious concrete pavement in the "breathe in-breathe out" design for sponge cities in China.

Sponge city construction is an ideal approach to mitigate the degradation of urban water environments. Among road materials, permeable concrete pavement stands out due to its unique structure that allows rainwater runoff to flow through its pores. This paper analyzes the current application status and the prospect of different permeable pavement designs in China's sponge cities, aiming to offer valuable insights for urban planning and construction. Statistical analysis summarizes the spatial-temporal distribution patterns of urban flooding disasters in China and their causes. By comparing the characteristics and advantages of pervious concrete pavement with traditional concrete pavement, the potential of permeable concrete pavement in sponge city construction is summarized through case studies. The findings highlight that by adjusting the pore size, permeable concrete pavement can collect rainwater while filtering impurities, thereby purifying surface runoff. The range of the pervious coefficient should ideally fall within the range of 4~8 mm/s. In addition, the pavement's large contact area with the air and internal water evaporation contributes to its self-regulating capability, reducing the occurrence of extreme temperatures. Related experiments have shown that from 8 am to 12 pm, pervious concrete pavement can reduce the temperature by approximately 1 °C compared to conventional concrete. From 12 pm to 8 pm, this temperature difference increases to approximately 3 °C. To meet the needs of environmental protection and resource utilization, permeable concrete pavement can serve as an ideal tool to achieve green and low-carbon development.

Study on the Application of Environmentally Friendly Materials in the Construction of Sponge Cities in China and Their Impact on Rainwater Runoff

The concept of Sponge Cities has emerged as a pivotal response to the escalating urban water management challenges faced by cities globally, particularly in China. This innovative approach aims to create urban environments that mimic the natural water cycle’s absorptive and filtrative capacities, thus mitigating urban flooding, enhancing groundwater recharge, and improving water quality. Central to the realization of Sponge City objectives is the adoption of environmentally friendly materials designed to replace traditional urban infrastructure with permeable, sustainable alternatives. This paper provides a comprehensive review and critical analysis of the application of such materials within the Sponge City framework, assessing their effectiveness, integration challenges, and the multidisciplinary strategies required for successful implementation. Through a detailed discussion, this review highlights the potential of environmentally friendly materials in transforming urban landscapes into resilient, water-sensitive environments. It also delves into the necessity for robust policy support, public engagement, and education, alongside a multidisciplinary approach that encompasses urban planning, hydrology, environmental science, economics, and sociology, to address the complexity of urban water management challenges. This paper aims to shed light on the pathways towards amplifying the benefits of Sponge City initiatives, proposing strategies for broader implementation and suggesting future research directions to enhance urban resilience and sustainability.

Exploring Herbaceous Plant Biodiversity Design in Chinese Rain Gardens: A Literature Review

Amidst rapid urbanization and escalating environmental degradation in China’s urban areas due to climate change, traditional drainage systems struggle to cope with rainfall, resulting in frequent flood disasters. In response, rain gardens have emerged as ecologically practical stormwater management solutions that integrate urban flood control with landscape design. Leveraging the dual benefits of rainwater purification and aesthetic enhancement provided by vegetation, herbaceous plant-based rain gardens have assumed a pivotal role in green infrastructure. However, dedicated research on the application of herbaceous plants in rain garden design is limited, especially within China’s water-stressed context. This study employs a literature review and case analysis to explore this critical issue. Initially, it delineates the concept of the sponge city introduced by the Chinese government. Subsequently, it reviews concepts and methods of plant biodiversity design in urban settings and rain gardens and elucidates the structure and function of rain gardens. Four Chinese rain gardens in different urban environments (old industrial areas, university campuses, urban villages, and urban highway green belts) were selected to examine the selection and arrangement of herbaceous plants while identifying deficiencies in their designs. Finally, feasibility suggestions are provided for the design of herbaceous plant diversity in Chinese rain gardens. This study’s findings can provide a reference for the planting design of herbaceous plants in rain gardens for other countries and regions with similar climates and environmental conditions.

Modelling the behaviour in socio-technical systems for policy assessment - A comparison of modelling approaches using the example of Sponge City concept implementation

How are policies affecting the social behaviour of actors and thus the dynamics of the corresponding socio-technical systems? This question is of central relevance to understand what policies might be effective for sustainable transitions and transformation where social changes are immanent. Exploratory modelling approaches such as agent-based modelling (ABM) are suitable and established to analyse how individual, especially heterogeneous behaviour emerges to affect social systems. In contrast to this micro-level perspective of understanding how social behaviour influences system behaviour, System Dynamics models (SDM) focus on the macro-level perspective by analysing how system interactions drive complex system behaviour. Qualitative modelling approaches such as Causal Loop Diagrams belonging to the Systems Thinking Modelling (STM) toolbox remain descriptive but need much less effort for model development. In this article, we compare how the different approaches ABM, SDM and STM can model social behaviour in socio-technical systems and what different kind of insights can be gained to assess the efficacy of policies. It discusses the advantages and limitations of the different approaches for their application in behavioural public policy modelling for sustainability transition. Therefore, three exemplary models (STM, SDM, ABM) are created for the same topic of implementation dynamics of adaptation measures to foster rainwater retention (Sponge City concept) in a multi-residential quarter. As a result, the risk of green gentrification is identified. Three hypothetical policies are implemented to illustrate the differences between the three modelling approaches for their use in policy assessment. Based on that, we discuss how the three modelling approaches conceptualise behaviour in general.

Harnessing the runoff reduction potential of urban bioswales as an adaptation response to climate change

Nature-based solutions (NbS), including China's Sponge City Program (SCP), can address the challenges urban communities face due to surface runoff and flooding. The current capacity of SCP facilities in urban environments falls short of meeting the demands placed on communities by climate change. Bioswales are a form of SCP facility that plays an important role in reducing surface runoff by promoting infiltration. This study assesses the potential of SCP facilities to reduce runoff in urban communities under climate change using the storm water management model. The study site in Ningbo, China, was used to evaluate the potential role of bioswales in reducing runoff risks from climate change. We found that bioswales were most effective in scenarios when rainfall peaks occurred early and were less effective in right-skewed rainfall events. The overall performance of SCP facilities was similar across all climate scenarios. To maintain the current protection level of SCP facilities, bioswales would need to cover at least 4% of the catchment area. These findings from Ningbo provide a useful method for assessing NbS in other regions and indicative values for the increase in the bioswale coverage needed to adapt to climate change.