Application and Trend Analysis of Sponge Cities in Alleviating Urban

Waterlogging

Xinyu Tian

Arts, Design & Architecture, University of New South Wales, Sydney, New South Wales, 2052, Australia

Keywords: Sponge City Program, Porous Design, Green Roof, Contiguous Open Green Spaces.

Abstract: As global urbanization intensifies, urban flooding has become a significant issue. The concept of the sponge

city, now implemented in China, draws on the experience of various established Western models and is

tailored to suit China’s unique context. However, as this concept is relatively new, there are still many aspects

that remain underdeveloped. This article primarily utilizes a literature review to analyze the current

application of sponge cities and the challenges they may face in the future. The findings indicate that four key

measures are commonly employed in China’s sponge city initiatives: expanding urban green spaces,

implementing green roofs, using permeable materials, and enhancing operational management. Given China’s

vast geographic diversity, a one-size-fits-all approach to managing urban flooding is impractical. However,

the use of permeable materials has emerged as the most widespread solution. Although the sponge city concept

is still in its early stages and faces numerous challenges, it holds the potential to significantly influence future

urban development.

INTRODUCTION

Since the 19th century, with the advent of

industrialization, rapid population growth, and swift

urbanization, scholars have extensively explored the

relationship between cities and rivers. Urban

waterlogging primarily results from precipitation

exceeding the city's drainage capacity. As China's

reform and opening up deepened, the urbanization

rate surged from 10.64% in 1949 to 57.4% in 2016,

exacerbating urban waterlogging issues across the

country (Yan etal, 2020). The five main contributing

factors include geographical location and urban

climate, planning, construction practices,

management, and detection systems (Wang, 2022).

As urban waterlogging becomes increasingly severe,

it poses significant threats to the quality of life, as

well as the safety of life and property.

In recent years, significant climate changes and

large-scale human activities have exacerbated urban

waterlogging, threatening human life and socio-

economic development. During urban flooding

events, many factors influence river conditions. As

the water levels rise, urban obstacles such as vehicles,

railways, and industries severely impact water flow,

https://orcid.org/0009-0001-7610-7168

leading to increased losses (Zhu, 2017). For instance,

the 1976 Big Thompson Flood in Colorado, USA,

resulted in record-high mortality rates due to the

vehicles (Albano, 2016).

Urban waterlogging is partly caused by

urbanization preventing natural water infiltration,

leading to a rapid increase in surface runoff. Many

regions have implemented traditional and innovative

measures to strengthen urban drainage systems and

develop water diversion and storage projects to

alleviate urban flooding. Cities like Singapore have

built specialized water diversion pipelines and

storage facilities to reduce the burden on downstream

drainage (Gruntfest, 2020). Additionally, new

technologies and concepts such as Low Impact

Development (LID) in the United States, Water

Sensitive Urban Design (WSUD) in Australia, and

Sustainable Urban Drainage Systems (SUDS) in the

United Kingdom have appeared (Tortajada, Joshi,

2013). These approaches, often integrated with the

local ecological environment, effectively address

urban waterlogging issues. By imitating the roles of

sponges in natural ecosystems, the idea of a "Sponge

City" seeks to improve urban water resource

management and flood control while lowering

214

Tian, X.

Application and Trend Analysis of Sponge Cities in Alleviating Urban Waterlogging.

DOI: 10.5220/0013281100004558

Paper published under CC license (CC BY-NC-ND 4.0)

In Proceedings of the 1st International Conference on Modern Logistics and Supply Chain Management (MLSCM 2024), pages 214-218

ISBN: 978-989-758-738-2

pollution and urban waterlogging. Given China's vast

land area and diverse geographical conditions, it is

not feasible to directly replicate Western governance

models. Although China's Sponge City concept was

introduced later than Western models, it has

incorporated and adapted many Western ideas to

better suit China's specific needs.

The features of sponge cities include wetlands,

forests, lakes, green roofs, bioretention systems, and

permeable pavements (Fletcher,2015). Sponge city

technologies and concepts in China focus on

enhancing urban permeability. Permeable pavements,

which account for 30% of the urban area, effectively

mitigate floods caused by heavy precipitation

(Liang,2020). However, Due to the complexity of

sponge cities, they face lots of challenges when

applied to real cities. Sponge city development is a

long-term endeavour that calls for increased tolerance

and assistance all along the way.

This article primarily explores the key

applications of sponge city concepts within urban

environments. The impact of urban waterlogging is

reduced by the sponge city approach's guiding

principles. Firstly, the use of permeable materials on

urban roads plays a crucial role in reducing the strain

on drainage systems. Secondly, from a sustainable

development perspective, integrating natural

ecological cycles with urban planning helps to

counteract the negative effects of urbanization. In

summary, sponge city strategies represent a major

direction for future urban development. Although the

challenges that exist today, their long-term benefits

are undeniable.

THE CURRENT

DEVELOPMENT OF SPONGE

CITIES

Urban water problems have gotten worse in China in

recent years due to the country's almost

unprecedented level of urbanization. Rapid

urbanization has altered land use patterns, resulting in

a deteriorating water environment. The hardening of

urban land surfaces has reduced water infiltration,

increasing runoff, and leading to higher flood peaks

and volumes The Chinese government responded by

proposing the idea of Sponge City in 2013. (Liu, Jia

& Niu, 2017). The Sponge City aims to effectively

manage urban rainwater by balancing the natural

environment with urban planning. The application of

green infrastructure, which includes several processes

like retention, storage, purification, and reuse before

discharge, is central to Sponge City's tenets.

According to studies, these actions can recover 70–

90% of precipitation on-site, increasing urban

resilience during periods of intense precipitation.

(Jiang & McBean 2021).

The material used for the pavement is essential to

this idea. For Sponge Cities, a few novel pavement

materials have been developed, including permeable

cement concrete, permeable asphalt concrete, and

others. These materials are distinguished by their

porosity, pore size, and related properties. It is

possible to modify pore size, connectivity, curvature,

and porosity to better fit different urban contexts

(Guan, Wang & Xiao 2021). These materials are

more expensive than conventional paving materials,

but they also have advantages including good noise

reduction and water and air purification.

Implementing sponge city principles in urban

areas can significantly enhance hydrological

performance and has broad applicability. Global

variations in seasonal patterns, temperature,

precipitation, and the frequency of severe weather

events, such as heavier rainfall, are already signs of

the consequences of human-caused climate change.

The rapid expansion of urban areas has exacerbated

water security issues and catastrophic flooding, a

stark contrast to the 1980s when 60% of the

population lived in rural regions (Jiang & McBean,

2021). This increased urbanization intensifies the

risks associated with extreme weather. A key

advantage of the sponge city approach is its ability to

balance precipitation and drainage effectively,

promoting greater water infiltration.

APPLICATIONS OF SPONGE

CITIES IN MITIGATING

URBAN FLOODING

In Sponge Cities, many measures are implemented to

reduce urban flood disasters, with many similarities

to LID and SUDS. The four major measures in the

sponge city concept are mainly contiguous open

green spaces, green roofs, porous design and

management.

3.1 Contiguous Open Green Spaces

Green spaces in urban areas offer numerous benefits,

both ecological and economic. Human's mental

health could be improved by green environments.

Research from Midtown Manhattan provides

evidence that sociocultural features of urban living,

Application and Trend Analysis of Sponge Cities in Alleviating Urban Waterlogging

215

such as disorganization, may impact mental health

(Galea, Ahern, Rudenstine, Wallace & Vlahov 2005).

Economically, areas with more green space generally

have higher property values and reduced heating and

cooling costs. Importantly, the extent of green space

in a city determines the overall health of its

ecosystem.

In the concept of Sponge Cities, green spaces

typically include public parks, sports fields, vacant

lots, road verges, and similar areas. Research by

Richard and others indicates that major gradients of

urban densification and topography are significant

factors influencing the availability and quality of

urban green spaces (Davies, Barbosa, Fuller, R,

Tratalos, Burke, Lewis & Gaston 2008). As

populations grow rapidly, urban areas cannot avoid

high-density modern buildings. In Sponge City,

governments should prioritize housing policies that

reduce high-density construction and preserve

existing trees and large shrubs within development

areas.

3.2 Green Roofs

Green roofs in Sponge Cities are primarily used for

rainwater collection on rooftops. In China, many

cities experience significant rainfall, so green roofs

not only help collect rainwater but also effectively

reduce the building's water costs. A case study by

Weiyu presented a green roof model and tested it on

their school dormitory (Zhan, Ye, Wu, Yan & Zhu

2023). Their model could save approximately

227,500 yuan annually in water costs. The model’s

principle involves collecting rain from the roof

through a system that includes a base layer, thermal

insulation layer, screed layer, waterproof layer,

irrigation system, planting soil layer, and vegetation

layer. This green roof model captures rainwater and

uses it and vegetation to supply water for the

building’s toilets and reduce rooftop runoff.

Therefore, the widespread use of green roofs can

significantly help in water conservation and

managing heavy rainfall in the area.

In green roofs, various materials are used, each

with its own characteristics. Spraying polyurea as a

waterproofing material can effectively prevent roof

cracking and extend the roof's lifespan. Porous PVC

drainage plates, known for their excellent cost-

effectiveness and drainage performance, ensure that

rainwater is quickly diverted, preventing water

accumulation. For example, the application of

polyurea through spraying can efficiently mitigate

roof cracking, while the porous PVC drainage plates

provide great economic advantages and physical

characteristics. According to Data Envelopment

Analysis by Lijuan Huang, spraying polyurea

waterproof material is one of the best ways to green

roofs (Huang, He, Tang, Fu & Li 2020). In

conclusion, green roofs play a necessary role in the

Sponge City concept such as contributing to rainwater

management, energy savings, and environmental

improvement.

3.3 Porous Design

This aspect is crucial for porous design in the concept

of Sponge Cities. To meet Sponge City requirements,

pavement materials need to have properties such as

permeability, retention, purification, evaporation, and

drainage (Guan, Wang & Xiao 2021). This presents a

challenge for pavement engineering. Previously,

many cities used permeable vegetation, but this has

gradually been replaced due to development needs.

Additionally, this change has worsened the urban heat

island effect and increased urban flooding.

The concept of permeable pavements is designed

to absorb and retain water when it rains and to

evaporate it when there is no rainfall (Brunetti,

Šimůnek & Piro 2016). This design helps reduce

flood risks and mitigate the urban heat island effect.

Although this concept is advanced, it poses

challenges for material development. Permeable

asphalt concrete, permeable cement concrete,

permeable bricks, and novel materials utilizing

polymer binders are just a few of the permeable

pavement materials that are currently accessible.

(Guan, Wang & Xiao 2021). These materials are

characterized by their porosity, pore size, pore

distribution, connectivity, and curvature. Engineers

choose materials based on local soil and terrain

conditions. Despite the promising nature of the

porous design, these materials are significantly more

expensive than traditional ones, and there is a need to

develop new materials with better load-bearing

capacities.

3.4 Management

In addition to utilizing the technologies in Sponge

Cities, effective management is also crucial. An

efficient management system can optimize the

various technologies used in Sponge City. Thu Thuy

Nguyen and colleagues propose a comprehensive

management model with several key components.

First, it is important to strengthen monitoring and

evaluation systems to collect a range of data

promptly. Tools for decision support must be created

by researchers to implement Sponge Cities

MLSCM 2024 - International Conference on Modern Logistics and Supply Chain Management

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sustainably. These tools can help decision-makers

and designers effectively allocate suitable

technologies and resources. Next, urban ecosystem

services should be assessed, including biodiversity,

urban cooling, and overall ecosystem health, to

determine their economic benefits. Standards for

implementing Sponge Cities should then be

established. Due to the great geographic diversity of

China, each city is unique, and rules should be

adjusted to account for local conditions to ensure that

Sponge City technologies effectively reduce flood

risks and the negative effects of the urban heat island

effect. Finally, developing and promoting Sponge

City construction should be based on comprehensive

data. The concept of sustainable development is a

mainstream development idea in the 21st century,

making the advancement of Sponge City applications

inevitable.

FUTURE PERSPECTIVES

The Sponge City concept is relatively new in China,

and it addresses urban water issues and effectively

improves the ecological environment. However,

implementing this concept presents several

challenges, particularly in technology, funding, and

policy. From a technical perspective, incomplete data

collection across different regions has resulted in

imperfect models for many sponge cities. For

example, while some permeable pavement materials

have performed as expected, many still fail to

withstand heavy loads. Future iterations will require

developing new materials with both higher

permeability and greater load-bearing capacity. In

terms of funding, insufficient financial resources have

been one of the major obstacles to implementing

sponge cities in China. The research and deployment

of many emerging technologies, such as green

materials for green roofs, demand significant

investment. Additionally, some technologies are still

underdeveloped, leading to high maintenance costs.

A lack of management experience has further

contributed to escalating costs. Regarding laws and

policies, the lack of close cooperation between

government entities and the inadequate integration of

relevant agencies have hindered progress. Many

policies remain fragmented, which is limiting

community participation and reducing the potential

for public-private partnerships. The Chinese

government could involve more private enterprises to

mitigate the financial and operational pressures on

government entities. Overall, although the sponge

city concept is innovative and promising, it also has

many unpredictable challenges. As the benefits of

sponge cities develop gradually, achieving

sustainability and realizing their full potential

benefits may need long-term investment and

continuous development.

CONCLUSION

The concept of sponge cities is relatively new in

China. The application of sponge city has grown

rapidly in recent years and made it increasingly well-

known. This article presented the key measures

adopted by sponge cities and the challenges might

face in the future. Urbanization and climate change

have led to a rise in the frequency of urban flooding.

Therefore, it has prompted the need for innovative

solutions like the sponge city approach, which

integrates established methods such as WSUD,

SUDS, and LID. Key strategies include the

development of interconnected green spaces, the use

of green roofs, porous urban structures, and advanced

water management systems. Expanding urban green

spaces enhances local ecosystems and offers multiple

benefits. Green roofs not only collect rainwater but

also contribute to urban greening. Among these

measures, porous design is especially effective,

because it mitigates the hardening of urban surfaces

by incorporating permeable materials. Overall, these

strategies play a key role in promoting sustainable

urban development. However, the sponge city

concept is still in its early phases and faces a few

challenges, especially when it comes to materials and

technology. While China's approach is well-suited to

its specific needs, there is still a lot of work ahead.

Therefore, the long-term benefits are clear and hard

to ignore.

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