In this article, we will be navigating through the 15 fastest-sinking cities in the world while covering the reasons behind land subsidence. If you wish to skip our detailed analysis, you can move directly to the 5 Fastest Sinking Cities in the World.
Sinking of Land and its Causes: An Analysis
Land subsidence, the shrinking of the land surface, is a rising issue with serious consequences. As reported by National Geographic, the surface of the Earth tends to sink as a result of multiple reasons. Relative sea level rise refers to the combined effect of land subsistence and rising sea levels and further aggravates the issue.
The sinking of land could be due to human activities such as the construction of cities over soft sediments and the pumping of groundwater. Groundwater extraction is a common reason behind land subsidence globally. When water is drained from underground aquifers, the pores tend to shrink under the earth’s weight. The severity is evident from the fact that 4 inches of subsidence takes place in parts of Mexico City every year because of this extraction. Extraction of hydrocarbons from the pores can also lead to subsidence.
Human development has been cited as the most significant reason behind sinking surfaces. Developments on peatlands are at a higher risk of facing subsidence. The problem is also prevalent in squishy river deltas hosting major cities such as Shanghai and Jakarta. Earth’s natural movement has also driven sinking. For instance, an ice sheet was witnessed to weigh down at the center of North America in the last ice age thereby making the coasts rise before it melted. This caused two millimeters of annual subsidence along the eastern coast as well as in New York.
Simultaneously, geography plays an additional role in this regard. The construction of a major portion of Mexico City over a filled-in lake and the sinking of the surface depict the effect of geography on subsidence.
The Adversities of Land Subsidence: Flooding
Cities where subsidence has been common will be witnessing severe flooding sooner than expected. Region-wise, the fastest subsidence has been reported in South, Southeast, and East Asia. Other regions including North America, Europe, Africa, and Australia also face this subsidence. With land subsiding faster than the rising sea level, those residing in coastal areas are at a higher risk of both flooding and sea level rise. The rise in sea level as a result of climate change is expected to even increase the proportion of those prone to floods. You can also take a look at some of the most vulnerable countries to climate change.
According to a study, published on March 6 in the scientific journal Nature, more than half a million people will be at risk of repeated flooding across 32 coastal cities in the United States alone, due to sinking ground and rising sea levels. Other countries with the highest flood risk have also been discussed. The sea level along the US coastline has been forecasted to rise 10 to 12 inches on average in the next 30 years. This worsens the situation in the already sinking land areas, considering the fact that more than 30% of the country’s population lives in coastal cities. High-tide flooding is expected to impact a population of 59,000 to 263,000 people on the US Atlantic coast. Simultaneously, an extra 110,000 to 225,000 people will get exposed along the US Gulf coast. Population exposure of 6,000 to 30,000 people has been predicted for the Pacific coast cities. You can also view the most disaster-prone countries in the world.
Protection Against Probable Hazards
Keeping the aforementioned forecasted scenario in mind, protection against flood peril becomes necessary. Companies that help protect properties from water and flood damage include Tokio Marine Holdings, Inc. (OTC:TKOMY), Zurich Insurance Group Ltd (OTC:ZURVY), and Chubb Limited (NYSE:CB). Let’s take a look at what these firms have to offer in terms of protection.
Tokio Marine Holdings, Inc. (OTC:TKOMY) is a multinational insurance holding company based in Tokyo, Japan. Private flood solutions from the company offer broader coverages which include business income or additional living expense coverage. Insurance rates with deductible options from $1,000 to $100,000 are available. Furthermore, elevation certificates are not needed. Tokio Marine Holdings, Inc. (OTC:TKOMY) effectively addresses the insurance needs of single-family homeowners, commercial property owners, and tenants through its private flood programs.
Zurich Insurance Group Ltd (OTC:ZURVY) is a known multi-line insurer serving people and businesses in more than 200 countries and territories. Other than providing insurance protection, the company offers prevention services in order to promote well-being and enhance climate resilience. The company’s residential private flood insurance program enables customizing coverage as per needs. Coverages offered include dwelling, other structures, personal property, ordinance, and loss of use. Optional coverage is also offered by Zurich Insurance Group Ltd (OTC:ZURVY) which allows repairing the structure with flood-resistant materials after the flood has taken place. Additionally, there is no waiting period for the company’s residential private flood insurance.
Chubb Limited (NYSE:CB) is one of the largest property and casualty insurance companies worldwide. The firm’s personal flood insurance offers up to $15 million in total property coverage. For special possessions such as art, collectibles, and jewelry, the insurer provides higher-than-average limits. In case residing in the house is not possible, additional living expense coverage pays up to $7,500 for temporary residence, meals, and other expenses. Chubb Limited (NYSE:CB) also pays the replacement cost for damaged property and possessions up to the limit on the policy.
Now that we have analyzed the reasons behind land subsidence, its harmful consequences, and the necessary precautions that could be undertaken, we can move to the 15 fastest sinking cities in the world.
15 Fastest Sinking Cities in the World
Our Methodology:
In order to compile a list of the 15 fastest-sinking cities in the world, we sourced data from the Geophysical Research Letters which reports on major geoscience disciplines. We selected the maximum subsistence rate in cities as our metric. The metric has been expressed in millimeters per year. Hence, the fastest sinking cities have been ranked in ascending order of their maximum subsistence rates, expressed in millimeters per year.
15 Fastest Sinking Cities in the World
15. Chennai
Maximum Subsidence Rate: 15.53 Millimeters Per Year
Chennai serves as the capital of Tamil Nadu and ranks as one of the fastest-sinking cities in the world. The maximum subsidence rate for the city was reported to be 15.53 millimeters per year. The size of the low-elevation area subsiding faster than 2 millimeters per year in Chennai was 38.38 square kilometers.
14. Alexandria
Maximum Subsidence Rate: 16.53 Millimeters Per Year
Alexandria ranks as another rapidly sinking city in the world. The Egyptian city is situated at the western edge of the Nile River Delta. Alexandria holds 122.24 square kilometers of low-elevation area subsiding faster than the sea level is rising.
13. Quanzhou
Maximum Subsidence Rate: 16.61 Millimeters Per Year
The city of Quanzhou is positioned in southern Fujian, People’s Republic of China. 16.61 millimeters per year is the maximum subsidence rate in the city. Therefore, Quanzhou ranks as one of the 15 fastest-sinking cities globally.
12. Bangkok
Maximum Subsidence Rate: 17.15 Millimeters Per Year
Bangkok is one of the most populous cities in Thailand. The city has been sinking fast which is evident from more than 1000 square kilometers of its low-elevation area subsiding faster than 2 millimeters annually.
11. Dhaka
Maximum Subsidence Rate: 18.29 Millimeters Per Year
Dhaka is the capital of Bangladesh and faces the issue of land subsidence. The maximum subsidence rate in Dhaka was recorded at 18.29 millimeters per year, the 11th highest among other cities.
10. Houston
Maximum Subsidence Rate: 19.47 Millimeters Per Year
The US state of Texas hosts Houston which ranks among the fastest sinking cities in the world. Although organized remedial action limited subsidence in Houston in the 1970s, the city still tends to have a maximum subsidence rate of 19.47 millimeters annually.
9. Kerala
Maximum Subsidence Rate: 19.57 Millimeters Per Year
Land sinking has also been seen to take place in Kerala. 793.14 square kilometers of low-elevation land is subsiding in the city faster as compared to the increasing sea level while 3,281.98 square kilometers is the land area where elevation is below 10 meters.
8. Kobe
Maximum Subsidence Rate: 22.64 Millimeters Per Year
Kobe is a part of Japan and ranks as one of the rapidly sinking cities worldwide. The city has 41.86 square kilometers and 25.28 square kilometers of land area where elevation is below 10 meters and 5 meters respectively.
7. Chittagong
Maximum Subsidence Rate: 23.52 Millimeters Per Year
The maximum subsidence rate in Chittagong was reported to be 23.52 millimeters per year. The Bangladesh-based city has 44.28 square kilometers of low-elevation area subsiding faster than 2 millimeters per year. Thus, Chittagong is another city with rapidly sinking land.
6. Hanoi
Maximum Subsidence Rate: 24.45 Millimeters Per Year
Hanoi is one of the populous cities of Vietnam and has a significant size of the low-elevation area which has been rapidly subsiding. While the maximum subsidence rate in the city is 24.45 millimeters per year, the total area with elevation of less than 10 meters was 1,695.51 square kilometers.
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Disclosure: None. 15 Fastest Sinking Cities in the World is originally published on Insider Monkey.