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Does Jakarta Have any Viable Options to Defend Itself From Ocean Inundation?

This narrow retaining wall is all that keeps the Java Sea (left side) from flooding Maura Baru (right side) in north Jakarta. The sea is at least six feet higher than the road. Photograph by Christina Leigh Geros.

JAKARTA, Indonesia–Walking along the wall that protects north Jakarta from the sea, it is impossible to ignore the enormity–and immediacy–of water-related issues that this megacity faces. The city's current plan of action, outlined by Wendy Koch in a recent article entitled, "Could a Titanic Seawall Save this Quickly Sinking City?," is widely criticized as being a costly solution to the misdiagnosis of sea level rise rather than the extreme rates of groundwater extraction that are sinking the city. With a 35-year construction timeline and a U.S. $40 billion-plus price tag, it is unlikely that these debates will end anytime soon. However, any architectural or engineering project of this scope requires more than one possible solution. So, what other options have been considered to save Jakarta from the sea?

Three principal solutions considered by the National Capital Integrated Coastal Development Project, as illustrated by the master plan drafted in April 2014.

Starting from the left in the illustration above, the three principal solutions offered by the National Capital Coastal Development Project are: complete abandonment of north Jakarta, dike reinforcement along the current coastline, and a new offshore barrier. While each option presents itself as a long-term solution, the ultimate success of any plan relies on immediate action from the city in two key areas: strengthening the existing hydrological management system so as to keep the city above water during the long and costly construction period; and strict regulatory policy and enforcement to stop groundwater extraction practices that would reduce the city's alarming rate of land subsidence -- currently averaging 7.5 cm (3 inches) per year -- which, if not stopped, will eventually undermine the effectiveness of any one of these options.

Jakarta's options to defend itself from ocean inundation are costly and each has serious tradeoffs; How to choose? Tweet this

Abandoning north Jakarta includes the abdication of an estimated $103-billion of real estate in a 5-km swath of the city, nearly reaching the National Monument of Indonesia (Monas). Some 4.5 million people would have to be relocated. Perhaps unsurprisingly, the financial burden–and loss–of such a strategy has been deemed heavy enough to look for better solutions.

To the right, the houses sit atop the city's old seawall, replaced not long ago by the wall to the left. Currently, the existing water level is near the top of this latest iteration of seawall, topping over twice a week at high tide. Photograph by Christina Leigh Geros.

Strengthening the existing coastline also requires the construction of equally high (up to 7-meter; 23 feet) river dikes farther inland. It would also be necessary to construct a new, elevated bridge infrastructure throughout the city and roughly 10,000 hectares of retention ponds with a large pumping capacity to keep the existing polders from flooding.

All of these implementations would have to take place in an already densely populated city; therefore, requiring the relocation of a similarly large percentage of the city's population. In addition, the doubtful end of groundwater extraction means that the amount of land needed for water retention would increase proportionately to continued rates of subsidence.

What other options have been considered to save Jakarta from the sea?Tweet this

Lastly, the option to build a new, offshore barrier in the Bay of Jakarta allows the city to remain largely untouched while placing not only a wall between the city and the sea, but also an enormous water-retention area (waduk) as well. Like the other options, this one has its challenges, such as cost. However, by conjoining the seawall project with a series of land reclamation projects, the city is able to partially fund the work through private investments while also strengthening the seawall in mass and form–giving rise to The Great Garuda.

Reflections of the city in Waduk Pluit, a large retention pond along the northern edge of Jakarta. Photograph by Christina Leigh Geros.

Few would argue the need to act, but to be effective the actions must strike at the core of the problems.

Jakarta suffers from three types of flooding. Most commonly, the city falls victim to flooding caused by insufficient water storage or management, meaning that nearly any amount of rainfall exceeds the capacity of an inadequate drainage system. The second most common type of flooding results from high water discharges upstream, insufficient river dikes, and clogged streams and pumps–all contributing to regularly occurring overflows. The third–least common and most localized–type of flooding comes from the sea. Even during the catastrophic flood events of 2007, where parts of the city were inundated by sea water, the majority of flood damage was not caused by the sea. This event called attention to the staggering rate of land subsidence in Jakarta with sea-level rise lurking in the wings.

Rivers sink with the land they traverse and water follows the natural pull of gravity. Regardless of the placement and form of the line between Jakarta and the sea, as long as the land sits below the sea, the delta–Jakarta's very foundation–will be unable to naturally drain. Every time a new set of gymnastics is engineered for a body of water, an enormous amount of energy is required to put that plan into action. How much energy will it take to keep Jakarta afloat? Tweet this

Existing water pump infrastructure protecting Jakarta's coastline. Photograph by Christina Leigh Geros.

Christina Leigh Geros, from Cambridge, Massachusetts, is a Fulbright-National Geographic Digital Storytelling Fellow based in Jakarta, Indonesia. She is a designer, researcher, and educator whose project gives voice to the communities of the Ciliwung River through an interactive website mapping stories that expose the relationships between urbanism, ecology, and politics.

Follow my daily explorations of Jakarta on Twitter and Instagram: @clgeros

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