Sinking Cities: Ground Subsidence Threatens U.S. Urban Areas
Table of Contents
- Sinking Cities: Ground Subsidence Threatens U.S. Urban Areas
- Sinking Cities: An Expert Guide to Ground Subsidence in Urban Areas
- What is Ground Subsidence?
- Why is Ground Subsidence Happening in U.S. Cities?
- Which U.S. Cities are Most Affected by Ground Subsidence?
- How is Ground Subsidence Measured?
- What are the impacts of Ground Subsidence?
- How Does Groundwater Extraction Cause Ground Subsidence?
- What Role Does Climate Change Play?
- Are There Any Solutions to Address Ground Subsidence?
- Is Ground Subsidence a Global Problem?
- Where can i read more?
- Research Details
A new study reveals that meaningful ground subsidence, or sinking, is occurring in all 28 of the most populous cities in the United States.Researchers attribute this phenomenon to a combination of natural geological shifts, groundwater extraction, and the increasing weight of urban infrastructure.The study emphasizes the urgency of implementing mitigation strategies, particularly in regions facing worsening drought conditions due to climate change.
Researchers at the Virginia Institute of Technology, after surveying over 600,000 locations, discovered that both coastal and inland cities are affected.this challenges the common perception that rising sea levels are the sole threat to coastal communities.
The research indicates that at least 20% of the total area within these 28 cities is sinking, with 25 cities exhibiting subsidence across 65% of their area. This affects an estimated 34 million residents. In certain locations,the ground is sinking at a rate of 10 millimeters per year.
Advanced Satellite Data Reveals Subsidence Patterns
The study utilized data from the European Space Agency’s Sentinel satellite, employing a radar system known as insar (Interferometric Synthetic Aperture Radar). This technology allows for the detection of minute vertical movements of the Earth’s surface, measured in millimeters.
Analysis of the InSAR data identified Houston as experiencing the most severe ground subsidence.More than 40% of Houston’s area is sinking at a rate exceeding 5mm annually, with 12% subsiding at double that rate. Some areas are sinking as fast as 5 centimeters per year. Similar subsidence patterns were observed in Fort Worth and Dallas, Texas.Las Vegas, the Washington D.C. area, parts of San Francisco, and the vicinity of LaGuardia Airport in New York City are also affected.
Groundwater Extraction: A Primary Driver
Researchers identified groundwater extraction as the primary cause of the observed subsidence, accounting for approximately 80% of the sinking. The depletion of water from underground aquifers, without adequate replenishment, creates voids that lead to soil compaction and surface sinking. In some cities, including New York, the weight of buildings also contributes to the problem. In Texas, petroleum and natural gas extraction exacerbate the issue, according to the study.
In eight major cities – New York, Chicago, Los Angeles, Phoenix, Houston, Philadelphia, San Antonio, and Dallas – over 60% of the population resides in areas affected by ground subsidence.Researchers believe this subsidence has contributed to the increased frequency of major flooding events,with these cities experiencing over 90 such events as 2000.
Leonard Ohenhen,a Ph.D.from Virginia Tech, warned that continued population growth, increased water consumption, and drought conditions exacerbated by climate change will likely worsen ground subsidence. “As cities continue to grow, more areas will become susceptible to ground subsidence,” Ohenhen stated.
The study also highlights the threat to infrastructure posed by differential ground movement, which can damage aqueducts and other vital systems.San Antonio was cited as a specific example.
Addressing the Crisis: Groundwater Management and Mitigation Strategies
Natural factors also play a role. The retreat of massive ice sheets that once covered much of North America is causing a slow rebound effect, with areas previously depressed by the ice now rising. Conversely, the periphery of these formerly glaciated regions is sinking at a rate of 1 to 3 mm per year. Cities such as New York, Indianapolis, Nashville, Philadelphia, Denver, and Chicago are experiencing this phenomenon.
Matt Prethard, a professor of Earth Physics at Cornell University, told Scientific American that the effects of subsidence are accumulating noticeably. “It’s been 10 years since 2015, and the number has begun to accumulate,” Prethard said.
The researchers recommend managing groundwater demand as a basic step in mitigating ground subsidence. They point to Tokyo, which experienced severe subsidence of up to 4 meters since 1900, as an example of triumphant intervention. Tokyo implemented strict groundwater regulation policies in 2000, effectively curbing the sinking.The study authors emphasize the urgency of similar measures, particularly in drought-prone regions like texas. They also advocate for eco-friendly infrastructure, such as improved drainage systems and artificial wetlands, to reduce flood damage and building codes that account for ground movement.
A Global Problem
Ground subsidence is not limited to the United States. It is indeed also a significant issue in China and Japan.
A study by Chinese scientists analyzing Sentinel satellite data across 82 cities with populations exceeding 2 million revealed that 45% of these cities are experiencing ground subsidence. The average sinking rate was 3mm per year, with 16% subsiding at a rate of 10mm or more. Groundwater extraction and the weight of urban progress were identified as the primary causes. In Indonesia, the capital city of Jakarta is sinking so rapidly that the government is planning to relocate the capital to Borneo Island.
An international collaborative study, led by the Spanish Lipology Institute and published in the journal *Science*, projected that by 2040, 12 million square kilometers – 8% of the Earth’s surface – will have a greater than 50% chance of experiencing land subsidence. The areas at greatest risk include the inland sedimentary basins of the North China Plain, the Gulf Coastal Zone of Mexico, the Vietnamese and Egyptian Mekong and Nile deltas, and parts of the Netherlands, Mexico, and iran.
Robert Nichols of the University of East Anglia stated that “19% of the world’s population is influenced by ground subsidence.”
Sinking Cities: An Expert Guide to Ground Subsidence in Urban Areas
Ground subsidence, the gradual sinking of land, is a growing concern in many urban areas worldwide.This article delves into the causes, consequences, and potential solutions to this alarming phenomenon, focusing on the situation in the United States and beyond.
What is Ground Subsidence?
Ground subsidence is the sinking or settling of the ground surface.It’s a gradual process that differs from sudden events like sinkholes. This occurs due to a variety of factors, primarily the compaction of subsurface materials.
Why is Ground Subsidence Happening in U.S. Cities?
A recent study reveals a concerning trend: ground subsidence is occurring in all 28 of the most populous cities in the U.S. Several factors contribute to this issue, including:
- groundwater Extraction: Removing water from underground aquifers is the primary driver, causing soil compaction.
- Natural Geological Shifts: Some areas are naturally sinking due to geological processes.
- Weight of Urban Infrastructure: Buildings and other structures add pressure to the ground.
- Natural Factors (Ice sheet rebound): Areas are sinking after ice sheets retreat.
Which U.S. Cities are Most Affected by Ground Subsidence?
While many cities are experiencing subsidence, some face more significant challenges. According to research, these cities are among the most affected:
- Houston, TX: Experiencing some of the fastest subsidence rates, with over 40% of the city sinking.
- Fort Worth & Dallas, TX: Neighboring cities are also affected by subsidence.
- San Antonio, TX: Showing areas of significant subsidence, threatening infrastructure.
- Las Vegas, NV: Facing subsidence issues.
- Washington D.C. Area Is showing a sinking trend in local areas.
- New York City (near LaGuardia Airport): Experiencing concerning subsidence patterns.
How is Ground Subsidence Measured?
Researchers use advanced technology to monitor ground movement. The European space Agency’s Sentinel satellite plays a crucial role, using a radar system called InSAR (Interferometric Synthetic Aperture Radar). This technology can detect minute vertical movements of the Earth’s surface, measured in millimeters, providing valuable data about subsidence patterns.
What are the impacts of Ground Subsidence?
The consequences of ground subsidence are far-reaching, impacting both infrastructure and the habitat. these include:
- Increased Flood Risk: Subsidence increases the vulnerability of cities to flooding, especially during heavy rainfall or storms. Subsidence has likely contributed to the increased frequency of flooding events with 90 such events occurring since 2000.
- Damage to Infrastructure: Ground movement can damage, aqueducts, roads, buildings, and other vital city systems.
- Threat to Residents: approximately 34 million residents in the cities studied are affected by ground subsidence.
How Does Groundwater Extraction Cause Ground Subsidence?
Groundwater extraction is a primary driver of ground subsidence. Removing water from underground aquifers creates voids. This leads to soil compaction and causes the ground surface to sink. Without adequate replenishment, the soil collapses.
What Role Does Climate Change Play?
climate change is exacerbating the problem in several ways:
- Worsening Drought Conditions: Droughts intensify water scarcity, driving increased groundwater extraction.
- Increased Flood Risk: Rising sea levels, combined with land subsidence, increase the likelihood and severity of flooding events.
Leonard Ohenhen from Virginia Tech warned that continued population growth, increased water consumption, and drought conditions exacerbated by climate change will likely worsen ground subsidence.
Are There Any Solutions to Address Ground Subsidence?
Yes, several strategies can help mitigate the effects of ground subsidence:
- Groundwater Management: Implementing strict regulations on groundwater extraction is crucial. Looking to Tokyo as an example the implementation of strict regulations was accomplished.
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Eco-Pleasant Infrastructure: Improved drainage systems and the construction of artificial wetlands can reduce flood damage.
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Building Codes: Implement building codes that account for potential ground movement.
- Population control: Reducing population growth would in-turn reduce water consumption.
Is Ground Subsidence a Global Problem?
Absolutely. While this article focuses on the U.S.,ground subsidence is a significant global issue,affecting many countries:
- China
- Japan (Tokyo has a great success story to learn from!)
- Indonesia (Jakarta is sinking rapidly,prompting a planned capital relocation)
- Mexico
- Iran
- Netherlands
- Vietnam
- Egypt
Robert Nichols of the University of East Anglia states that “19% of the world’s population is influenced by ground subsidence.”
