As Asian cities sink, managed retreat must be tabled
Even as Asia's megacities continue to submerge, officials of one small Philippine city are planning a major US$460 million reclamation project that will damage or sink their beautiful seaside city into the dark blue southern sea.
Scientists and environmentalists have called on the local government of Dumaguete to scrap the reclamation project, citing the devastating impact it may have on the marine environment and coastal communities. The 174-hectare project seeks to develop the site as a "5G-ready mini-city, complete with shopping malls, condominiums, esplanades and other business establishments."
This is developing as rising sea levels and climate change are posing serious threats to the population and economy of several Asian coastal cities—Bangkok, Dhaka, Jakarta, Manila and Shanghai, among them.
Threats come from a combination of tropical cyclones, storm surges, high tides and sea-level rise that increase risk of serious flooding by 2030. Some 600 million people worldwide—the majority in Asia—will be affected by rising sea levels in flood-prone coastal regions, some of them economic centers.
Sinking cities, rising seas
Imperceptible to most residents, major Asian cities continue to slide under water for a variety of causes. As global warming comes, scientists worry that the world is heading towards a perfect storm of sinking cities and rising seas in a decade.
This is not a new story, of course. More than a decade ago in 2008, some South-East Asian coastal nations were concerned about how vulnerable they were to the forces of the seas. In one of the early conferences on the problems of coastal cities, scientists from Indonesia, Malaysia, the Philippines, Singapore, Thailand, Vietnam and Japan studied the impact of sea flooding on migration from coastal areas.
The study focused on migration as a response to the sinking cities. The idea was that people would leave their homes voluntarily and migrate to safer places to avoid the rising seas. The study said Vietnam was in a class by itself with a high coastal plain population. By 2040, it was expected to experience a relatively high land loss due to submergence forcing people to migrate.
According to the study, by 2100 the continuing sea level rise was expected to result in a loss of wetland area with nearly 22 million people experiencing floods every year in Malaysia, Thailand and the Philippines.
The causes of the sinking cities and rising seas are not quite the same though the impacts are similar—submerging large areas of cities and populations under water in a decade or sooner. As cities plan their retreats, the big cities slowly sink at different rates, some faster than others.
Jakarta reportedly holds the record for the world's fastest sinking city, at a rate of around 25.4cm per year. Around 40 percent of the city now lies below current sea levels. Over half of its 10.6 million people lack access to piped water and surface water is heavily polluted, so they dig illegal wells to extract groundwater. Rains are not enough to replenish water in the soils because over 97 percent of Jakarta is covered in asphalt and concrete.
Bangkok with its 9.6 million population is also vulnerable to rising sea levels. Six years ago, in 2015, its government published a report that said the city could be underwater in 15 years. The city, now only around 1.5 meters above sea level, is sinking at a rate of about two centimeters per year. Bangkok's sinking has been made worse by the sheer weight of its high-rise buildings which pressing into the sea the foundations of the city. The city has about 700 buildings with 20 floors or more and 4,000 buildings with 8—20 floors, putting considerable pressure on the land on which they sit.
Manila with its core city population of 13.3 million people is sinking at around 10 centimeters per year. Since the city has an average elevation of around five meters it is living on borrowed time. The sinking increases the risk of floods and cause high tides to penetrate further inland and water to recede more slowly. Unless there is intervention, much of the land area bordering Greater Manila Bay—Pasay to Manila to Malabon to most of Bulacan province north of Manila—will go under several centimeters of water by 2050.
Bangladesh's capital city of Dhaka, population 18.9 million, is another low-lying, riverside city in Asia beset by a sinking feeling caused by unsustainable extraction of groundwater. As in other cities they exploit groundwater because the rivers are polluted. The city is sinking at a rate of about 1.4 centimeters per year, with most urbanized areas a mere 6–8 meters above sea level. Sea level rise appears to be happening at a rate ten times greater than the global average in the Bay of Bengal, southwest of the city.
Managing retreat from rising seas
There is still time to prevent a worst-case scenario if people act now. Governments and corporations must immediately transition to large-scale renewable energy to keep the world's temperature rise under 1.5 degree Celsius.
Governments can do this if they phase-out coal-fired power plants and accelerate the shift to clean and renewable energy. Governments must upgrade their nationally determined contribution targets promised in the Paris Agreement ahead of COP26.
As seas rise and climate change brings rains and floods, countries must now plan strategies to protect their communities. They have a variety of defenses to choose from: protection (e.g., hard shoreline dikes), accommodation (e.g., elevating or flood-proofing structures), or managed retreat. 4
Managed retreat for now seems to be a last resort. This basically means relocating people and infrastructure away from vulnerable coastal areas to flood-free ecosystems—out of harm's way before disasters strike.
For instance, about two years ago, the Indonesian government announced that they are planning to develop a new capital in Kutai Kertanagara in East Kalimantan at an estimated cost of US$33 billion. The new city will relocate some 1.5 million people mostly civil servants and their families and economic actors. However, it seems that there is no commitment on the poor coastal folks in North Jakarta which will be left to deal with the unsolved land subsidence and rising seas.
Certainly, a managed retreat should be inclusive for all especially the most vulnerable and impoverished who are left with little choice but to sink or swim hard to survive.
Sea level rise up to four times global average for coastal communitiesProvided by SciDev.Net
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