① In Asian Countries, Active Subsidence is Occurring
Tianjin, one of the major cities in China, is among the fastest-sinking cities in the world.
This phenomenon is primarily due to excessive groundwater extraction, a common problem in many urban areas. Groundwater plays a crucial role in supporting the structure of the land. When removed, the underlying sediment compresses and settles.
Tianjin and Shanghai, one of the most developed and populous cities in China, have been experiencing severe land subsidence for over a century. Since its early days as a trading port, the city has been sinking gradually due to increased groundwater usage exceeding the land’s capacity.
By 1921, Shanghai had sunk by 8.5 feet, with groundwater extraction accounting for about 70% of this subsidence. The physical weight of skyscrapers, which comprise the remaining 30%, is another cause of the city’s sinking. Shanghai’s situation is a broader issue affecting more than 50 cities across China.
In response to the sinking problem, Shanghai has taken several measures. Despite these efforts, the city continues to struggle with ongoing development and the rise of the global sea level.
The 1995 Hanshin earthquake significantly impacted Kobe, Japan, causing extensive damage to infrastructure and loss of life. As a result, the urban areas of Kobe underwent extensive reconstruction and recovery efforts. This process involved rebuilding physical structures and addressing long-term city planning and community involvement.
Kobe presents an interesting case. Unlike most places, the sinking was not the result of human intervention but a consequence of nature. Port Island, where Kobe Port was located, sank due to the earthquake.
The nearby Kansai and Kobe airports are more significant than Kobe. According to the most recent statistics discovered since 2008, the sinking rate was 2.75 inches yearly. The island where Kansai Airport was built has already sunk 38 feet. If the sinking rate remains 2.75 inches, the airport is estimated to stay above water for approximately 335 more years.
② Serious Cases in Indonesian Cities
Semarang in Indonesia has become one of the fastest-sinking cities in the world due to land subsidence issues. The city is sinking by 0.78-1.18 inches annually. The combination of sinking land and rising sea levels puts over 2 million city residents at risk of flooding, causing serious damage to homes and infrastructure.
Groundwater extraction is the main cause of subsidence in Semarang. Additionally, the natural consolidation of alluvial soil and pressure from building weights contribute to the problem. Restoring subsided areas to their previous levels is realistically impossible.
The Semarang government is implementing programs to address these issues. For instance, they have initiated a program to “normalize” the rivers, which includes constructing canals to increase drainage speed and manage floods more effectively. Work is also underway to restore mangrove forests along the Semarang coastline, which protect from coastal erosion and floods.
Jakarta, Indonesia, one of the fastest-sinking cities in the world, faces severe challenges. Visitors should check out the city’s convenient and affordable hotels to witness its current state. The primary factor causing this astonishing situation is the excessive extraction of groundwater.
This excessive withdrawal is mainly due to the city’s piped water resources system failing to serve a significant portion of the population. As a result, about 65% of Jakarta residents rely on groundwater, causing land subsidence when water is pumped from the underground aquifers. This causes the land above to sink, exacerbated by the weight of heavy buildings and urban development on the city’s soft soil.
Rising sea levels due to climate change are another significant issue exacerbating Jakarta’s sinking problem. The Jakarta regional government has been attempting to regulate groundwater extraction and find alternative water resources to address these issues. One key plan is the NCICD (National Capital Integrated Coastal Development) program, which involves constructing a giant sea wall in the northern part of the city.
However, this project is criticized for its potential impact on local fishermen and its limited ability to address the land subsidence issue directly. Given the current-sinking rate, Jakarta could be submerged within approximately 460 years.
③ It’s Happening in Vietnam too
Vietnam’s largest metropolis is sinking worryingly, causing serious difficulties for its infrastructure and residents. The city is experiencing land subsidence at a rate of 0.78-1.96 inches per year, much faster than the global average sea-level rise of 0.14 inches per year at the upper limit. This rapid sinking is particularly concerning as it significantly increases the risk of flooding as sea levels rise due to climate change.
Several factors contribute to Ho Chi Minh City’s subsidence, with the key being excessive groundwater extraction. As the city rapidly expanded, water demand exceeded the supply of the water system.
Another factor is that the city is located in a flat delta region, with 40-45% of the area less than 3.28 feet above sea level. This geographical location makes it particularly vulnerable to heavy rains, storms, and sea-level rise.
To address these issues, authorities have implemented measures to reduce groundwater extraction, such as expanding piped water distribution across the city. This has significantly reduced the rate of groundwater extraction, playing a crucial role in slowing additional subsidence.
Hanoi, the cultural capital of Vietnam, is experiencing significant land subsidence mainly due to excessive groundwater extraction. This excessive groundwater extraction is a response to increased demand for water resources due to the city’s rapid population growth and urbanization.
Research by scientists at the University of California, Irvine, using NASA’s GRACE satellite data, emphasized that more than a third of the Earth’s largest aquifers, including Hanoi’s, are affected by unsustainable usage. Due to excessive groundwater extraction in Hanoi, parts of the city have sunk by over 3 feet, forcing the demolition and reconstruction of apartment buildings in the affected areas.
Hanoi’s situation is exacerbated by water quality pollution and inadequate flood management infrastructure, lagging behind the city’s rapid development. This has led to serious water-related issues, such as a decline in the city’s livability and downstream agricultural productivity.
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