Jakarta suffers subsidence rates of up to 17cm a year in some areas, threatening the homes of 4.5 million people.

To make matters worse, the land on which they live is sinking into the sea.

“We don’t want to move from here,” Benjol says, but his community may have no choice. Straddling north Jakarta’s flood defences, they are vulnerable to the high tides that last year breached the dyke, exacerbating the annual wet season floods.

North Jakarta suffers subsidence rates of up to 17cm a year in some areas – caused by the excessive extraction of ground water from the soft soil on which the city is built – meaning whole neighbourhoods will be several metres underwater by 2030. The homes of 4.5 million people are threatened with permanent inundation.

‘Giant seawall’

To avert this disaster, Indonesia’s outgoing government last month rushed to commence the construction of its futuristic $40bn “giant seawall” development, otherwise known as the National Capital Integrated Coastal Development (NCICD).

Comprised of a 25km dyke that will close the bay of Jakarta and 17 man-made islands shaped into a “giant garuda” – a mythical bird used as Indonesia’s national symbol – the development is set to become one of the world’s largest infrastructure projects.

Its first phase of strengthening the city’s existing defences began last month, and the sealing off of Jakarta bay is expected to be completed by 2022.

To bankroll the scheme, predominantly mid and high-end housing developments will be sold off; eventually housing up to 1.5 million people on the giant garuda. The ambitions for the development cannot be understated – with the NCICD master plan pushing for Indonesia’s “seat of government” to be relocated from central Jakarta to the new city.

However, the plans have drawn significant criticism, with detractors claiming the seawall is a bogus solution that will once more displace traditional fishermen and other low-income groups from their communities.

The People’s Coalition for Fisheries Justice Indonesia (KIARA) says thousands of people such as Benjol will be removed from their homes to make way for what they see as just another luxury housing development.

The government has defended the initiative, saying 17 percent of the new development will be devoted to social housing, and will give fishermen closer access to the cleaner waters 6km out to sea – where the seawall is to be constructed.

The likelihood of the city’s poorest being housed on the giant garuda seems limited, but it’s a social injustice most Jakartans are likely to forgive if they can be assured that the seawall will prevent the capital from sliding into the sea.

That, however, cannot be guaranteed.

The project seeks to prevent Jakarta’s inundation by two means: firstly by blocking out the ocean, and secondly by boosting water supply so that ground water extraction may be reduced – thus reducing average subsidence rates of 7.5cm a year.

Fetid rivers

To achieve this second goal the bay, once sealed, will be converted into a giant “freshwater” reservoir fed by 13 rivers that flow through the city and out into the bay. However, the success of creating this alternative source of potable water – and perhaps the success of the entire project – may rely on the Indonesian government’s ability to clean up West Java’s fetid rivers.

Jakarta’s brown-and-black, plastic-strewn waterways are fed primarily by the Citarum River, cited in 2013 as one of the world’s top 10 most-polluted sites next to the Niger Delta and Chernobyl.

Addressing a seminar recently, acting Governor of Jakarta Basuki “Ahok” Tjahaja Purnama said he “had his doubts” about the project, as reported by the Jakarta Post, comparing it to a similar seawall project in South Korea where he said engineers had struggled to prevent the formation of a “lake of mud”.

For the model to work in Jakarta, water pollution levels must be reduced by between 75-95 percent.

If the NCICD fails to convert the bay of Jakarta into a beautiful freshwater reservoir then alternative sources of piped water must be found or ground water extraction will continue and Jakarta will continue to sink. The NCICD master plan concedes that the planned outer wall can only protect Jakarta until 2080, unless the subsidence stops.

Purba Sianipar, assistant deputy minister of economic affairs, seemed unaware the project had such an expiry date when interviewed by Al Jazeera.

“I don’t know in what document you read that,” Sianipar said. “We never designed anything [based] on that short period of time. We would like this seawall dyke to exist for not only 100 but 1,000 years to protect the city.”

‘Limited warranty’

The minister was later disappointed when he conferred with Victor Coenen, project manager for Witteveen Bos, a Dutch engineering firm that has helped Jakarta create the project’s master plan.

“He called me back [to check] actually,” Coenen told Al Jazeera. “But no, infrastructure projects are the same as all products, they have a limited warranty.”

“I hope for Jakarta that the land subsidence will stop because [if it does not] by then [2080] you will be talking about another five metres to seven metres of water in front of Jakarta city, and those are levels that you really have to wonder if you can still protect yourself against.”

Inundation by the sea is also only one front on which Jakarta is fighting a battle to stay above water. Every year, Jakarta’s rivers break their banks as floodwaters surge through from West Java. There are concerns that capping the exits to these rivers may exacerbate seasonal flooding.

The problems of sea inundation, flooding, water pollution, and water supply are intricately interlinked, and the success of the giant sea wall is bound to factors far beyond the control of its project managers.

“It’s about who will own the project. I’m not sure if the companies involved have the capacity to provide a complete solution. Unless the problem is dealt with as a national commitment, it won’t go anywhere,” Arif Shah, a representative for Greenpeace Indonesia, said.

Shah added coordination would be required among the president’s office, national planning agency, the Environment and Forestry Ministry, and the provincial governments of West Java, Banten, and Jakarta.

“Unless all the parties sit down together, then it’s hard to make this solution happen.”