Subsidence and the threat to the construction industry

Land subsidence, the gradual sinking or settling of the ground’s surface, is emerging as a global crisis that threatens the integrity of infrastructure and urban planning worldwide. From the luxury high-rises of Miami to the sinking megacities of Asia, subsidence is reshaping our understanding of construction challenges in the face of natural and man-made pressures, writes John Ridgeway.

Subsidence occurs when the ground beneath a structure loses its ability to support weight. This can result from natural processes such as tectonic activity, soil compaction, or the erosion of underlying materials. However, human activities like groundwater extraction, mining and rapid urbanisation have exacerbated the problem.

Globally, subsidence impacts over 6.3 million square kilometres of land, threatening billions of dollars and pounds worth of infrastructure and displacing communities. This alarming rise in subsidence incidents underscores the need for urgent action by the construction industry – just look at the facts.

In Miami, several luxury high-rises, including the iconic 57-story Porsche Design Tower and Arte Surfside, are showing signs of subsidence. Reports indicate that parts of Miami’s coastline are sinking at rates of up to 3 millimetres annually. This phenomenon gained global attention after the tragic collapse of the Champlain Towers South in Surfside in 2021, which was linked to structural failure exacerbated by subsidence.

Enhanced building codes are being introduced in the US to factor in subsidence risks. Authorities are also investing in monitoring technologies, such as LiDAR and satellite imaging, to detect early signs of ground movement. In addition, developers are exploring new construction materials and techniques that are more resilient to shifting ground. Despite these efforts, Miami’s vulnerability highlights the urgent need for a massive shift in urban planning and construction, but this is not a local situation – it is a global problem.

Subsidence in Asia

Asia’s rapidly expanding cities face some of the world’s most severe subsidence challenges. In Jakarta, Indonesia, sinking is being recorded at an alarming rate of up to 10 centimetres per year. Jakarta’s subsidence is driven by excessive groundwater extraction and the weight of urban development. Parts of the city are already below sea level, leading the Indonesian government to plan a $34 billion relocation of the capital to Borneo. As a further response Jakarta has introduced groundwater management policies and plans to construct sea walls to protect sinking areas.

In China, more than half of Beijing is sinking, also due to over-extraction of groundwater. The problem affects infrastructure such as roads, buildings and even historical landmarks like the Forbidden City. Beijing is now implementing water recharge systems, where treated wastewater is injected back into aquifers to stabilise the ground.

Mexico City has been coping with subsidence for over a century. Built on an ancient lakebed, the city sinks by an average of 10 inches annually, with some areas experiencing up to 20 inches. The extraction of groundwater to support the city’s 21 million residents has caused the soft clay beneath it to compress. Authorities here have invested in rainwater harvesting systems to reduce dependence on aquifers and have promoted the restoration of green spaces and the creation of urban wetlands to help mitigate the impact of subsidence. Despite these measures, the city faces enormous challenges in maintaining its infrastructure while addressing the root causes of subsidence.

Subsidence is not a new phenomenon. Venice, Italy has been sinking for centuries due to a combination of natural and human-induced factors. The MOSE Project, a series of movable flood barriers, aims to protect Venice from rising waters and subsidence-related flooding.

New Orleans, USA, was built on swampy ground and is sinking at rates of up to 6 millimetres per year. Engineering projects, such as improved levees and pumping systems, are being implemented to combat the issue.

Bangkok, Thailand’s ground level is dropping by 2-3 centimetres annually. The government there is now is investing in urban planning reforms, including restrictions on high-rise construction in vulnerable areas.

The role of modern construction processes

Sadly, modern construction techniques have inadvertently contributed to subsidence in several ways. High-density developments place immense pressure on unstable ground, accelerating sinking. Many construction projects also rely on groundwater extraction, which weakens subsurface materials. This is frequently exacerbated by urban expansion, which often occurs without comprehensive geotechnical assessments, leading to construction in high-risk areas.

If we are to address the subsidence crisis, the construction industry must adopt innovative practices and technologies, Comprehensive soil and ground assessments should be mandatory before construction. The use of advanced materials, such as carbon fibre and aerated concrete, can also reduce the stress on unstable ground and why not incorporate ancient building techniques, such as floating or raft foundations which distribute weight more evenly, reducing the risk of sinking.

Technological advancements can also play a crucial role in mitigating subsidence risks. Digital twins or virtual replicas of infrastructure would allow engineers to simulate various conditions and optimise designs. Sensors embedded in buildings can also detect early signs of subsidence, enabling proactive measures.

Most importantly, we need to recognise that subsidence is a global problem that requires coordinated efforts. International knowledge sharing using platforms like the Global Land Subsidence Network would facilitate the exchange of research and best practices. Governments must also enforce stricter regulations on groundwater extraction and land use and communities need to know more about the risks of subsidence and the need for more sustainable practices.

Subsidence is not just a geological issue - it is a human-made crisis exacerbated by unsustainable development practices. Addressing it requires a comprehensive approach that combines technology, innovation and policy reform. From Miami to Jakarta, the lessons are clear - we must rethink our construction methods and prioritise sustainability to safeguard our cities and their inhabitants.

As the construction industry faces this unprecedented challenge, the question remains - can we build a future where subsidence is no longer a threat, or will we continue to sink under the weight of our own progress? The answer lies in our willingness to innovate and adapt.