Cities at risk of sinking

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It is difficult to understand how a city of 10 million people can gather and move to a completely new island.

But Jakarta is not the only city with that gigantic task ahead. There are many others at risk of sinking around the world.

Indonesian President Joko Widodo announced this week that the country's capital will move to a site in the sparsely populated province of eastern Kalimantan, on the island of Borneo, known for its rainforests and orangutans.

Jakarta is sinking faster than anywhere else in the world and has to move because it is overcrowded and polluted.

Experts have labeled the plan as "very risky", warning that if the country is not careful it will create the same problems elsewhere.

Here is a look at the other cities at risk of going under.

NEW ORLEANS

The city is vulnerable to flooding because it is sinking, built on loose land and located near the coast.

Scientists say it is undergoing a rate of 1 cm per year.

The National Academy of Sciences designed in 2016 that New Orleans could be one of the most affected cities in the world along with Manila, Jakarta and Bangkok.

According to The Times-Picayune, in the 30's a third of the city was below sea level,

and when Hurricane Katrina hit, that number had reached about 50%.

Soil subsidence has deadly consequences, with several houses exploding in the city since 1975, injuring dozens of people. The buried gas lines twisted and broke, letting the gas accumulate in the cavities beneath the concrete slabs or pour into the attics.

MANILA

Scientists have reported that the average sea level in the Manila Bay suddenly increased at the end of the 60s.

In September 2009, tropical storm Ondoy brought rain for a month less than a day and left more than 80% of the city flooded with water.

Hundreds of people have been killed and thousands more have remained displaced.

The sinking is caused by the catastrophic subsidence of groundwater that is pumped from below, often through unregulated wells for houses, factories and farms.

The provinces of Pampanga and Bulacan have sunk between 4 and 6 cm each year since 2003, according to satellite monitoring.

BANGKOK

The Thai government issued a report three years ago warning that the capital could be under water within 15 years.

Although this may sound shocking, with an altitude of only 1.5 m above sea level and a sinking rate of 2 cm per year, the outlook for Bangkok does not seem good.

One of the culprits is the immense number of buildings in the city.

The Sinking cities The report revealed that around 700 buildings with 20 or more floors and 4000 buildings with 8-20 floors are exerting considerable pressure on the ground.

For the 10 million people living there, floods are a recurring and deadly problem.

The 2011 flood event cost the country $ 46 billion in repairs and rehabilitation, including $ 8 billion spent in Bangkok alone. More than 800 deaths were recorded and 13 million people were affected by the flood.

HOUSTON

The city has been sinking for decades.

According to data from the US Geological Survey, parts of the county of Harris, which includes the Texan metropolis, have decreased between 3 and 4 meters from the 20's.

Some areas sink up to 5 cm per year.

Like other sinking cities, Houston has drawn too many groundwater, leaving the region prone to severe flooding.

Houston is located in one of the largest subsidence tanks in the nation, and there are many smaller bowls that go down in height, leaving water in these areas.

SHANGHAI

The central financial district sank 2.6 million since 1921, when the first investigations were made.

Here too, excessive use of groundwater is an important factor, but there is also a lack of sediment recharge as sediments are trapped by upstream dams or extracted for construction material.

Like Bangkok, heavy buildings also play a role. In 2012, an 8 meter long crack opened at the foot of the Shanghai Tower project.

It is estimated that the sinking cost the city over 2 billion dollars between 2001 and 2010.

The subsidence affects over 50 cities, where 78,858 km2 of land fell by at least 20 cm.

LAGOS

A 2012 study revealed that because the coast of Nigeria is so low, a sea level rise of just 1-3 meters "will have a catastrophic effect on human activities in these regions".

The city with a growing population of 21 million – the most populous city on the African continent – is particularly vulnerable due to the lack of adequate drainage systems and subsidence caused by groundwater extraction.

Some estimates suggest that a 20 cm sea level rise could cause 740,000 people to lose their homes throughout Nigeria.

Its low coast continues to erode.

BEIJING

A 2016 study revealed that the city is sinking up to 10 cm in some areas every year.

Once again, like the other sinking cities, the problem is due to the depletion of groundwater, with an excessive extraction that makes the soil dry and compact.

The study found that Beijing was ranked as the fifth most stressed city in the world.

Groundwater is the main source of water for the city, with estimates that the capital requires 3.5 billion liters of water per year.

The rapid sinking could affect buildings and public works projects, including the city's rail network.

DHAKA

It is estimated that sea level rise could flood 17% of the city of Bangladesh, leaving around 18 million people displaced by 2050.

The city is sinking at a rate of 1.5 cm per year and, although this does not seem as dramatic as the situation in Jakarta, the sea level in the Bay of Bengal is rising 10 times faster than the global average.

Millions in the coastal areas of the city have already fled, migrating to the overcrowded slums of Dhaka. Like Jakarta, the situation is aggravated by the extraction of groundwater at an unsustainable rate, as well as by the displacement of tectonic plates.

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