Jakarta is not an Exemplar of Sea Level Rise

Brief Note by Kip Hansen — 26 January 2020

Ted Nordhaus has an excellent article in the Wall Street Journal titled “Ignore the Fake Climate Debate”.

[  It may or may not be pay-walled for you — if it is, try searching the title in your search engine and use the link provided by Google/Bing/whatever — it may let you in or see here. ]

Nordhaus presents a very pragmatic view of the climate debate — one I more or less agree with (devil is in the details…) — and certainly pragmatic solutions — summarized in the last paragraph with this:

“The world will tackle this problem the way that it tackles most other problems, partially and incrementally, by taking up the challenges that are right in front of us—adaptation, economic development, energy modernization, public health—and finding practical ways to address them.”

I write this Brief Note because the Wall Street Journal  illustrates Nordhaus’ piece with a stock photo from Getty Images with the caption of “A man walks on the seawall in Jakarta, Indonesia, built in 2017 in anticipation of rising sea levels. Photo: Anton Raharjo/NurPhoto/Getty Images”  [ you can see the image at this link].

Jakarta, Indonesia, is not an exemplar of rising sea levels    

 Jakarta is a good proxy for many of the problems that Asian cities are having with sea levels — relative sea levels.   Is Relative Sea Level a problem specific to Asian cities?  No, but it is a common problem to Asian mega-cities as can be seen in this figure:

The image above is from “Projection of coastal floods in 2050 Jakarta”, Takagi et al. [2016].  Tokyo suffered land subsidence of over 4 meters from 1910 up until 1965 or so, but has stabilized.  Manila and Bangkok are subsiding at the meter range.  Jakarta leads the pack having sunk over 3.5 meters (almost 12 feet) in the ten years between 1990 and 2000.

What’s going on in Jakarta?

An easy summary:

“Jakarta lies in a low, flat basin, averaging 7 metres (23 ft) above sea level; 40% of Jakarta, particularly the northern areas, is below sea level, while the southern parts are comparatively hilly.

Rivers flow from the Puncak highlands to the south of the city, across the city northwards towards the Java Sea; the Ciliwung River, divides the city into the western and eastern principalities. Other rivers include the Pesanggrahan, and Sunter high sea tides.

Other contributing factors include clogged sewage pipes and waterways that service an increasing population, in addition to deforestation near rapidly urbanizing Bogor and Depok in Jakarta’s hinterland.

Jakarta is an urban area with complex socio-economic problems that indirectly contribute to triggering a flood event.”

So,  40% of the city area is below sea level.  How did this happen?

“As a consequence of this rapid development Jakarta has been facing many urban development issues, though the issue of land subsidence appears to have become especially serious over the last couple of decades. In fact, the occurrence of land subsidence was clearly recognized as far back as 1978, when substantial cracks were found in buildings and a bridge in downtown Jakarta (Djaja et al., 2004). In Jakarta, the subsidence rates along the coast vary from 9.5 to 21.5 cm/year in the period between 2007 and 2009 (Chaussard et al., 2013). Land subsidence can be classified into four types, namely: subsidence due to groundwater extraction, subsidence induced by the load of buildings, subsidence caused by natural consolidation of alluvium soil, and geotectonic subsidence. For the case of Jakarta the first type, subsidence due to groundwater extraction, appears to be the main cause for the lowering of the land. In particular, the extraction of water for industrial uses is a widespread practice which can induce rapid rates of land subsidence. Such subsidence can lead to severe damage to buildings and infrastructures, increase the extent of flooded areas, destroy local groundwater systems or increase seawater intrusion (Braadbaart and Braadbaart, 1997; Abidin et al., 2009; Ng et al., 2012).”

North Jakarta has sunk an additional 2.5 meters in the last ten years, according to the BBC.

Jakarta is in serious trouble when it comes to Relative Sea Level — the land is sinking and sea levels in the Java Sea, while they are inconsistent — “rising and falling rate of sea level in the Java Sea are highly related to the events through ONI (Oceanic Niño Index) value.”  [ source ] — we can safely assume that as global sea level will continue to rise slowly as the world’s ocean temperatures rise ever so slowly, at their centuries long rate of somewhere about 2-3 mm/yr.

How much of Jakarta’s problem with the sea is due to Sea Level Rise?

Quoting Takagi et al. [2016],  “Projection of coastal floods in 2050 Jakarta”:

“The simulations demonstrate that by the middle of this century extensive floods could potentially reach several kilometers inland in Jakarta. Land subsidence is clearly one of the major challenges facing the city, as considering only the influence of sea-level rise indicates that such floods may be limited to within a few hundred meters of the coastline. From2000 to 2050 the potential flood extent is estimated to increase by 110.5 km2. Land subsidence is responsible for 88% of this increase.”

Land Subsidence 88%.  And the other 12%?

La Niña events, the 18.6 year lunar nodal high-tide cycle, and other abnormal tide mechanisms —  oh, and a little bit of sea level rise.

Bottom Line:

1. Jakarta, like many Asian mega-cities, is built on mostly swampy land where several rivers run into the sea. Skyscrapers and mega-cities should not be built on swamps — the soil beneath the city will compact and subside under the weight of modern  development.

2. Jakarta, like many Asian mega-cities, has been pumping fresh water out of aquifers directly beneath the city for decades. The city is sinking into the void created by this ground water extraction.

3. The government of Indonesia and the city fathers of Jakarta are fully aware that their problem is not global sea level rise. Only the international press, powered by climate change advocacy, dares make the claim against all evidence to the contrary.

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Author’s Comment:

Newspapers, whether printed or online, need images to break up all those boring words, boring words which many readers ignore after the first paragraph or two.  Today’s modern media rely on stock images for many of these photographs and often modify the captions to suit their content.  Such images are often, intentionally or not, propagandistic.

Readers of Nordhaus’ WSJ piece should not get the impression that Nordhaus thinks Jakarta is being threatened by climate change driven sea level rise based on the WSJ’s inserted image.

Some places in the world are threatened by even the small inexorable general sea level rise the world has experienced over the last few centuries.  See the first part of my series here on Sea Level: Rise and Fall and Miami’s Vice.

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