Why Are Chinese Cities Sinking? A Comprehensive Analysis of Causes, Effects and Solutions

Imagine towering skyscrapers, bustling streets, and a city alive with activity slowly sinking into the ground. This is the alarming reality in many of China’s major cities, including Shanghai and Tianjin. Rapid urbanization, industrial growth, and excessive groundwater extraction have triggered an environmental crisis beneath the nation’s booming cities. Earth.org explores the sinking cities of China, an issue that not only exposes the cost of unchecked development but also serves as a global warning for all rapidly growing urban centres.

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Imagine a city, its skyline dominated by skyscrapers and highways. Now, imagine it slowly drooping into the ground. This is not a sci-fi novel but a real problem facing many of China’s major cities. From the famous streets of Shanghai to the industrial hub of Tianjin, Chinese cities are sinking at an unprecedented rate.

Earth.org digs into the complex web of factors behind this urban subsidence, looking at the historical context, the speed of development, the consequences of industrialisation and the solutions being proposed to fix this problem. As we untangle this messy issue, we see how China’s drive for globalisation and economic power has inadvertently created an environmental crisis that threatens the very foundations of its cities.

It is not just a Chinese problem. It is a warning for all fast-developing countries. A reminder of the fine line between progress and protection.

Historical Context: Early Signs of Subsidence

The story of sinking cities in China did not start with the country’s explosive economic growth in recent decades. The first signs appeared nearly a century ago. According to research, cities like Shanghai and Tianjin have been subsiding since the 1920s. This early subsidence was subtle, and often overlooked amid the chaos of the early 20th century. But it laid the foundation for the bigger sinking we see today.

In Shanghai, historical records show that parts of the city had already sunk by 1.76 meters between 1921 and 1965. This early subsidence was mainly because of the extraction of groundwater to support the growing population and emerging industries. The soft, compressible soil of the Yangtze River Delta, where Shanghai is built, made the city more prone to this kind of settlement.

Tianjin, another coastal megacity, started to show subsidence in the 1930s. By the 1960s, parts of the city had sunk over a meter. Groundwater extraction was once again to blame, and it would only worsen in the following decades.

These early subsidence cases were the canary in the coal mine, warning of the bigger and more severe subsidence that would plague many Chinese cities in the late 1900s and early 2000s. 

Industrialization Era

In the mid-20th century, China underwent a transformation as it embarked on an industrialization path. Over this period, China’s urban landscape changed dramatically, especially between the 1950s and the 1970s. 

Cities that were once centers of trade and culture became industrial giants overnight.
China’s industrialization was crucial to its economic growth but the stability of metropolitan areas was inadvertently affected. With factories sprouting up and industrial output booming, water demand increased exponentially for industrial processes and to support the growing urban workforce. This led to even more groundwater withdrawal, which further worsened the subsidence problem that had started decades before.

According to a 2024 study, several Chinese towns experienced increased ground sinking during the period of rapid industrialisation. For example, the subsidence rate in Suzhou, a city west of Shanghai famous for its gardens, went from 13 millimeters/year in the 1960s to 67 millimeters/year in the 1980s. Massive land reclamation projects also started during this period. 

By filling in shallow waters and coastal marshes, cities like Tianjin and Shanghai expanded their land area. The reclaimed ground, which is soft and compressible, led to new areas that are very prone to subsidence, even as it provided much needed space for urban and industrial growth.

Development and Urbanization

In the late 20th and early 21st century, China experienced unprecedented urbanization, which would change the country’s landscape and worsen the problem of sinking cities. This period of fast development led to a construction boom, with entire cities seeming to appear overnight. This was needed to meet demand as millions of people moved from rural to urban areas.

According to the World Bank, China’s urban population grew from 191 million in 1980 to 831 million in 2018, 640 million in just four decades. 

Chinese cities’ skylines changed as skyscrapers and residential complexes replaced low-rise buildings and old neighbourhoods. In Shanghai, for example, the Pudong district with its futuristic skyline was largely built on farmland 30 years ago. The rapid vertical growth added weight to the already stressed ground, worsening subsidence.

Infrastructure development kept pace with the vertical growth. Huge networks of roads, bridges and tunnels were built to connect the ever-expanding urban areas. Shanghai alone built over 800 kilometers of metro lines between 1993 and 2018. While these projects improved urban mobility, they also involved a lot of groundwork and, in many cases, required continuous pumping of groundwater, which further worsened the issue.

The speed and scale of urbanization often outran urban planning and environmental protection. In many cases, construction went ahead without proper assessment of the ground condition or long-term impact on land stability. 

Population Growth

China’s rapid urbanization was driven by an enormous population shift from rural to urban areas. China’s National Bureau of Statistics reported that the country’s urban population was 902 million in 2020, 63.89% of the total population. This represents a huge jump from 1978, when only 17.92% of China’s population lived in urban areas.

This urbanization has put huge pressure on city infrastructure and resources. The demand for housing, water and other basic services in urban areas has gone through the roof. Many cities have had to tap into groundwater at unsustainable rates to meet this demand.

The concentration of population in urban areas has also led to a phenomenon known as urban heat islands, where cities are much hotter than the surrounding rural areas. This can exacerbate subsidence by increasing evaporation rates and water demand, further straining groundwater resources.

The sheer weight of the urban population and the infrastructure to support it is also putting pressure on the ground. High-rise residential complexes, shopping malls and office buildings are all adding to the weight on the ground, compressing soil layers and causing subsidence.

Race For Globalization

For the last century or so, one of the biggest stories has been China’s rise to economic superpower. Along with lifting millions out of poverty and changing the face of the global economy, this growth has also contributed to the problem of sinking cities. 

According to the World Bank, between 1978 and 2018, China’s GDP grew at an average annual rate of over 9%, making it the largest economy to have done so in history. The transition from a planned to a market-based economy, with a focus on manufacturing, exports and investments in infrastructure and urban expansion was the main driver of this growth. The pursuit of rapid economic growth often prioritized industrial output and urban expansion over environmental concerns. Cities were encouraged to grow quickly, attract investment, and boost their GDP figures. This led to a race among cities to build bigger, higher, and faster, often without full consideration of the long-term environmental impacts.

Skyscrapers and big buildings have played a part, too. China has over 50% of the world’s 100 tallest buildings, many of which are in sinking cities like Shanghai and Guangzhou. The weight of these buildings, combined with the groundwater extraction needed to build and operate them, has accelerated subsidence in many urban areas.

China’s Belt and Road initiative, a large-scale project to connect China to the rest of the world, has required massive infrastructure projects both within China and abroad. While these projects bring economic benefits, they also bring environmental and geological risks.

Consequences of Industrialization

Groundwater Extraction

In Beijing, for example, decades of over-pumping have led to a drop in groundwater levels of up to 100 meters in some areas, up to 70% of the land subsidence is caused by over-extraction of groundwater. Industries like agriculture and textiles that rely heavily on groundwater further lower the water table and permanently compress the land. In coastal cities like Tianjin, the consequences are sinkholes, infrastructure damage and seawater intrusion.

Mining Operations

In China, mining, especially coal mining, has contributed significantly to soil subsidence. Mining has caused over 25,000 square kilometers of land to sink, with some areas sinking by 8 meters. Underground tunnel collapse affects cities like Datong. Besides depleting groundwater, mining can also worsen subsidence by changing hydrology due to the weight of new reservoirs.

Overpopulation and Urban Density

China’s rapid urbanization has increased population density, straining resources like groundwater. High-rise buildings and infrastructure add weight, causing further ground compaction. Beijing faces significant groundwater extraction issues, with domestic water use contributing to this problem. Over-extraction of groundwater can lead to subsidence, which is a concern in numerous cities experiencing high groundwater use.

Urban Heat Islands 

Urban heat islands (UHIs) in cities like Beijing and Shanghai increase temperatures, driving up water demand and groundwater extraction. Elevated temperatures also cause soil shrinkage, and frequent heating and cooling cycles weaken urban infrastructure, contributing to land instability.

Natural Causes

Geological factors, such as soft sediments in coastal cities like Shanghai, make these areas more prone to subsidence when combined with heavy construction and water extraction. Sea level rise, projected to increase by up to 1.3 meters in some areas by 2100, compounds the issue, making cities more vulnerable to flooding and saltwater intrusion.

Current Statistics and Future Projections

• Shanghai: Parts of Shanghai have indeed sunk by more than 3 meters since 1921. Current subsidence rates vary across the city, with some areas sinking by up to 10 millimeters per year.
• Beijing: Beijing has experienced cumulative subsidence of up to 1.5 meters in some areas. Certain districts are still sinking at rates of up to 11 centimeters per year.
• Tianjin: This coastal city has seen total subsidence of up to 3.5 meters. Some areas continue to sink at rates of 5-7 centimeters annually.
• Wuhan: Wuhan has experienced subsidence of up to 50 centimeters in its worst-affected areas.
• Datong: This coal-mining city in Shanxi province has seen dramatic subsidence, with some areas sinking by as much as 8 meters due to mining activities.

Future Risks

Looking ahead, the prospects for many Chinese cities are concerning. Future projections must consider current subsidence rates and the compounding effects of climate change, continued urbanization, and economic development.

Research published in Nature Communications presents concerning projections for coastal regions in China. The study suggests that by the year 2120, if current subsidence rates persist, several major urban areas could face significant relative sea level rise. The Pearl River Delta region, home to important cities like Guangzhou and Shenzhen, might experience a rise of up to 1.7 meters. Shanghai, another crucial economic center, could see levels increase by as much as 1.5 meters. Additionally, the city of Tianjin may face a rise of up to 1 meter. These projections take into account both the effects of land subsidence and global sea level rise, highlighting the compound challenges these areas may face in the coming century.

Implications

A study by Climate Central estimates that by 2100, land currently home to 93 million people in China could be at risk of annual coastal flooding because of sea level rise.

The World Bank estimates that flooding in coastal cities could cost $1 trillion annually by 2050 if no action is taken. Chinese cities bear a significant portion of this cost. Critical infrastructure, including ports, airports, and power plants, may be at risk. For instance, Shanghai’s Pudong International Airport, built on reclaimed land, could face increased flooding risks.

Continued subsidence could also exacerbate saltwater intrusion in coastal aquifers, threatening freshwater supplies for millions of urban residents.

Wetlands and coastal ecosystems, crucial for biodiversity and natural flood protection, could be lost as cities sink and sea levels rise.

Innovative Solutions

China has been leading the way in creating and using creative solutions to the difficult problem of urban subsidence. These include urban planning techniques, legislative modifications, and the use of cutting-edge technologies to monitor and mitigate subsidence.

Groundwater Management

Given that groundwater extraction is a primary cause of subsidence, many cities have implemented strict controls on groundwater use:

1. Tianjin Model: The city of Tianjin has implemented a comprehensive groundwater management strategy that has become a model for other Chinese cities. This includes strict licensing and monitoring of groundwater extraction, the implementation of water-saving technologies in industries, and the development of alternative water sources, including desalination plants.
2. Artificial Recharge: Cities like Beijing are experimenting with artificial groundwater recharge systems. During periods of high rainfall, excess surface water is directed into underground aquifers, helping to restore groundwater levels.
3. Water Pricing Reforms: Many cities have implemented tiered water pricing systems, where heavy users pay higher rates. This encourages water conservation and reduces reliance on groundwater.

Building Regulations and Urban Planning

New regulations and urban planning strategies are being implemented to minimise the impact of urban development on ground stability:

1. Load Reduction: Shanghai has implemented regulations requiring new buildings to be lighter, using modern materials and construction techniques to reduce the load on the ground.
2. Pile Foundations: For larger structures, deep pile foundations that extend to more stable soil layers or bedrock are now often required.
3. Green Infrastructure: Cities are increasing green spaces and permeable surfaces to allow better groundwater recharge and reduce the urban heat island effect.
4. “Sponge City” Concept: This innovative urban design approach, piloted in several Chinese cities, aims to make cities more permeable. It includes features like rain gardens, permeable pavements, and green roofs to reduce flooding and aid groundwater recharge.

Technological Innovations

China is leveraging advanced technologies to monitor and address subsidence:

1. Satellite Monitoring: The use of Interferometric Synthetic Aperture Radar (InSAR) technology allows for precise monitoring of ground movement over large areas. This enables early detection of subsidence and more targeted interventions.
2. Big Data and AI: Advanced data analytics and artificial intelligence are being used to process vast amounts of data from satellite and ground-based sensors, allowing for more accurate subsidence predictions and risk assessments.
3. Smart Water Management: IoT (Internet of Things) sensors and smart meters are being deployed to monitor water use in real-time, allowing for more efficient water management and reduced groundwater extraction.
4. 3D Printing in Construction: Experimental use of 3D printing technology in construction allows for the creation of lighter yet strong structures, potentially reducing the weight burden on subsidence-prone ground.

Policy and Governance Innovations

Addressing urban subsidence in China requires not only technological solutions but also innovations in policy and governance. Many cities have established special committees that bring together experts from geology, urban planning, water management, and other relevant fields to develop integrated subsidence management strategies. Collaboration between government agencies, research institutions, and private companies is being encouraged to develop and implement innovative solutions. Stricter requirements for environmental impact assessments, including subsidence risk analysis, are also being implemented for new urban development projects.

While these innovative solutions show promise, the challenge of urban subsidence in China remains significant. Successful mitigation will require continued innovation, substantial investment, and a commitment to sustainable urban development practices.

Conclusion

The complicated problem of sinking towns in China is exacerbated by rising sea levels, geological circumstances, groundwater exploitation, and fast urbanisation. There is some degree of subsidence in about half of China’s main cities, which can have detrimental effects on infrastructure, raise the risk of flooding, and force out residents.

China has responded to the magnitude of the issue with bold solutions, such as sophisticated groundwater management, “sponge cities” for improved urban planning, and cutting-edge technologies to monitor and lessen subsidence. These initiatives provide insightful information for cities around the world dealing with comparable issues brought on by urbanization and climate change.

Key strategies moving forward include integrated approaches to urban planning, long-term solutions that account for future growth and climate scenarios, continued investment in technology, effective policy-making, and global cooperation. China’s experience in addressing subsidence provides critical lessons for urban planners worldwide as cities continue to grow in the face of environmental pressures.