As the NCICD1 plan morphed and evolved and stalled, Jakarta kept flooding, and attention shifted to the other side of the equation – stopping the city from sinking any further.

In charge of that rearguard action is Oswar Mungkasa. Tall and professorial, dressed in the military-style khakis of the city’s civil servants, Mungkasa is a 25-year veteran of national and regional government and Jakarta’s deputy governor in charge of spatial planning and the environment. Since 2017 he has also held the title of “chief resilience officer” – a wide-ranging role that gives him responsibility for fixing everything that threatens the running of the city, from rubbish collection to racial harmony to preparing for a giant earthquake. These challenges grow every year in proportion to the population; 200,000 people move to Jakarta each year, drawn by and adding to the city’s huge economic expansion. “The urbanisation process has been too fast. We cannot keep up,” Mungkasa says.

His role has hammered home just how fragile the megacity is. “If something happened in Jakarta, our food only lasts maybe one week,” he says.2

The mechanism by which Jakarta is settling into its foundations has been understood for decades. The soft soil underneath the city is held up by the pressure of water in aquifers and reservoirs deep below the surface. Removing that water lowers the pressure, and the land above it sinks. That issue is exacerbated by building heavy structures on the surface, and by coating it with impermeable materials, like concrete, which prevent water from seeping back down and recharging the subsoil reservoirs.

It is a challenge that has presented itself elsewhere, including in Tokyo and Venice. 

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• 1. ..., in 2013, several days of sustained rainfall overwhelmed the flood management infrastructure. Canals collapsed and clogged, and the flooding spread beyond the poorer, lower-lying areas of the city and into the central business district. Around 45 people died and thousands of households were evacuated.

  That stirred the government into action. The then-governor, Joko Widodo – now Indonesia’s president – ordered a large-scale renovation of the city’s rivers, reservoirs and flood canals, which had become fatally clogged by decades of an approach to waste management that mirrored the randomised sprawl of construction in the region. Controversially, under an initiative euphemistically called “normalisation” some informal settlements on riverbanks were bulldozed to widen the waterways. In Muara Baru, a four-metre-high wall was built on one bank of the Ciliwung, protecting the community on that side of the river from most of the smaller floods – although water still spills over in the wet season.

  At the same time, the national government began to look at coastal defence in earnest. It launched a new project, the National Capital Integrated Coastal Development, or NCICD, and called in a coalition of international experts, most of them from the Netherlands, which has turned its own centuries-old experience of protecting its low-lying shoreline into a global industry.

• 2. The sinking of the city is one of the most pressing challenges on Mungkasa’s slate. It is also one of the most intractable, a complex problem that involves dealing with some of the city’s longest-standing environmental issues. It all starts with clean water.