Sinking Cities
As sea levels rise due to the warming of our planet, cities in Asia are some of the places at great risk of being submerged
Rising sea levels have become synonymous with climate change. With the accelerated rise of global sea levels over the past 20 years – a direct consequence of warming climates largely driven by human activities – Asia stands in a precarious position with four out of five people projected to be affected living here.
Even if efforts to limit global temperature rise to below 2°C above pre-industrial levels is successful, global sea levels are expected to rise between one and three metres within the century, threatening both coastal communities and megacities around Asia and the world. ag
Jakarta, Indonesia
Average elevation: 8 metres above sea level
Population: 10 million
Sink rate: 25.4cm per year
Jarkarta has been dubbed the fastest sinking city in the world with 40 percent of its land lying below sea level. However, the loss of land, while made worse by rising sea levels, has been primarily caused by unregulated groundwater extractions and the sheer weight of the megacity’s infrastructure, resulting in the sinking of the city by four metres over the past three decades.
Measures in Place
Efforts to save the flood-prone city from sinking are underway with sea walls and artificial islands being constructed.
Dhaka, Bangladesh
Average elevation: 4 metres above sea level
Population: 17.6 million
Sink rate: 1.4cm per year
In the low-lying capital of Bangladesh, rising sea levels have already displaced people living in the lowest lying regions. This has resulted in an increase in the number of slum dwellers in the densely populated city.
Besides the sea level rise, much like Jakarta, Dhaka also suffers from unsustainable groundwater extraction, exacerbating the city’s subsidence. Another phenomenon, plate tectonics – the movement of the Burman sub-plate and the Indian plate – is also contributing to this subsidence. In comparison to water extraction, however, plate tectonics only has a very minor role to play as its effects result in the sinking of about 3 to 5 millimetres of land per year.
Measures in Place
The country has invested in early warning systems and storm shelters to be prepared for storm related deaths, but despite the efforts, sea level rise from climate change could potentially prove to be an almost impossible challenge to overcome.
Mumbai, India
Average elevation: 14 metres above sea level Population: Over 20 million
Sink rate: 0.25cm per year
With low-lying parts between six to eight metres above sea level, the bustling megacity could lose more than 25 square kilometres or 40 percent of its urban land when sea levels rise.
Population expansion and infrastructure developments contribute further to the situation and some low-lying parts in the central and south of Mumbai could become completely submerged.
Measures in Place
Efforts have been made to address the issue by building sea walls along the city’s shoreline, planting more trees, investing in beach nourishment as well as building artificial reefs and sandbags.
Shanghai, China
Average elevation: 8 metres above sea level Population: 10 million
Sink rate: 0.1 –0.3cm every year
Relatively low-lying, Shanghai is vulnerable to rising sea levels, resulting in the need for coastal dikes and flood walls for protection from frequent flooding. Besides subsiding from the weight of its own infrastructure, just like Jakarta and Dhaka, Shanghai has also been affected by excessive groundwater extraction; since 1921, the centre of its CBD has subsided by 2.6 metres.
Measures in Place
The city’s efforts to reduce or even reverse the sinking by using water from local rivers instead of underground has been largely successful. Pumping water back into the ground has also helped to reverse the subsidence with some areas being 11 centimetres higher than they used to be. The annual land subsidence rate has gone down from 9 centimetres to 1 centimetre. Despite this success, rising sea waters continue to remain a threat, with the need for preventive measures to be put in place to avoid catastrophic consequences.