Jakarta, a metropolis of millions
Photo: NASA Earth Observatory / Lauren Dauphin
Numerous megacities around the world are located by the sea: New York, Mumbai or Tokyo.
Jakarta and its metropolitan area with 32 million inhabitants is one of the most densely populated coastal cities in the world.
The Indonesian capital is located on the island of Java and its population is growing, as are its most pressing problems: rising sea levels and regular flooding.
Rising sea levels and heavy monsoon rains regularly cause urban districts to be flooded.
Tens of thousands of people have already been displaced as a result.
In 2007, more than 70 percent of the city was inundated by heavy monsoon rain.
One reason for Jakarta's water problem is its enormous growth: in the past 30 years the city has literally burst at the seams: since the 1990s, the population has more than doubled, and it had to build houses and streets.
The difference between the “Landsat” satellite image from 1990 (left) and the image from 2019 (right) is enormous; the suburbs extend far into former green spaces, forests and floodplains.
But cutting down the trees, sealing the surfaces and straightening the rivers comes at a price.
There are less permeable surfaces and drainage possibilities for rainwater.
Because people are now settling on former floodplains, there are no more floodplains.
Many rivers and canals have been narrowed or are regularly clogged with garbage - one of the reasons why the water overflows quickly when it rains heavily.
Monsoon in the hinterland, storm surges on the coast
But suburban flooding is not Jakarta's only problem.
The water also comes from the coast.
Because due to rising temperatures worldwide and melting poles, there is now an average rise in sea level of 3.3 millimeters per year.
There is also evidence that climate change is making storms and related storm surges and floods more likely.
Nevertheless, around 1,185 hectares of artificial land have been raised off the coast of Jakarta.
Much of the new space was used for high-quality housing developments and a golf course, said Dhritiraj Sengupta, a remote sensing scientist at East China Normal University.
However, these sought-after residential areas on and off the coast are also the most vulnerable.
It is already foreseeable that the raised islands and land reclamation projects will sink due to the rising sea level - in some cases up to 80 millimeters per year, as satellites and ground-level sensors have already been able to measure.
Even in storm surges, these construction projects are the first victims, warns the researcher Sengupta.
A master plan by the city administration even provided for the construction of 17 new islands and a huge protective dam around the bay in front of Jakarta.
That should protect the city from floods.
But the major project stalled - for ecological, economic and technical reasons.
The situation is now so hopeless that the government is looking for a new capital.
We are talking about a region on the island of Borneo.