Jakarta is dealing with the significant threat of yearly sea-level rise. With more than ten million people living in and around the city, Indonesia faces a difficult challenge. Jakarta has been sinking for decades, predominantly on the north coast, where the city meets the Java Sea. Here, many of the residents have lost their homes and livelihood. The people are forced to rebuild yearly as the seawater continues to push through the ground and damage everything around it.

Concrete walls have been built on the edge of the most affected coastal towns in a desperate attempt to stop the water from overflowing. The latest prediction; a large portion of the city (millions of homes) could be underwater by 2050! Models predict that 95% of North Jakarta could be submerged underwater by this time.

Imagine living on the coast, surrounded by water, yet you don’t have a sufficient supply of clean pumped water as a resident. Whilst rising sea levels play a role, a lack of access to water (a fundamental human right) plays a major part in this problem.

Let’s find out why.

What is one thing all megacities have in common? Concrete!

Unfortunately, this is a hugely underestimated issue. The rapid urbanisation of Jakarta is the cause of numerous problems, including traffic, pollution and floods.

The impact of continuous expansion can have major environmental consequences. The city’s expansion quickly saw a loss of agricultural land, including rice fields, a reduction in green space, and increased traffic and pollution. Furthermore, it made way for severe flooding and landslides.

After decades and billions of dollars later, the goal of a flood-free Jakarta continues to be elusive.
With climate change bringing more extreme and unpredictable weather patterns, flooding is expected to worsen if nothing is done.
Channel News Asia

The Rapid Urbanisation Of Jakarta

Jakarta is the largest metropolitan area in Southeast Asia, with thirteen rivers running through the lowland area located on the city’s outskirts. These rivers have long been a major cause of flooding and displaced those whose homes are along the waterways.

Major issues are:

A lack of future urban planning
A lack of policy regulation
Poor infrastructure
Low-lying coastal zones
Narrow roads
Inadequate stormwater drainage
Deforestation
Land subsidence

One major cause of Jakarta’s sinking is an issue called land subsidence. Lowlands are often densely populated, and land use represents a high economic value.

The shallow subsurface in these areas frequently contains young, compressible deposits. These soft deposits are particularly vulnerable to subsidence caused by natural compaction or anthropogenic activities.

Land subsidence is the sinking of discrete segments of the compressible underground surface materials caused by the consolidation of sediments and movement of earth materials under the surface.

Land subsidence is caused by effective stress in these sediments and affects numerous cities worldwide.

Forty-five cities in the USA and ninety-five cities in China are affected by land subsidence. But more concerning, eleven low-lying coastal cities are in danger of inundation by the end of the century due to subsidence. Jakarta is included on this list of cities, with calculated subsidence of 17 cm/year.

Jakarta is rapidly developing and dense urban areas are heavily impacted with traffic congestion.

What Causes Land Subsidence?

Land subsidence causes can be divided into two groups: natural factors and anthropogenic (human) factors. Natural causes are responsible for twenty-three per cent of subsidence worldwide, while human factors are responsible for seventy-seven per cent.

Natural Causes (23%)

Among natural drivers of land subsidence, we can mention:

Tectonic movement
Isostatic sediment loading
Natural compaction of Holocene deposits
Volcanic activities

Natural causes cover large areas, and they are correlated to the surface’s geology. They are characterised by homogeneous rates of subsidence that rarely exceed a few mm/year.

Human Factors (77%)

Anthropogenic subsidence is generally one order of magnitude faster than natural subsidence. It is mainly driven by intense land modifications in environments with compressible deposits.

Subsidence caused by fluid withdrawal such as groundwater, oil, or gas extraction can occur at high rates of up to tens of cm/year. Therefore, the faster the fluid is extracted, the faster is the decline in the fluid level and the faster the subsidence.

Mining & Oil (9%)

Underground excavation for mining and oil and gas extraction is responsible for the study of 9% of land subsidence cases. Some projects involved mentioned are:

Coal mines
Salt mines
Gas extraction
Oil extraction

Groundwater Extraction (59%)

Land subsidence is mainly induced by the over-exploitation of groundwater. Growing demands on groundwater resources due to urban and agricultural development are the main drivers of land subsidence. This situation gets worse in arid and semi-arid regions.

Groundwater drawdown produces a noticeable deformation, especially near highly populated areas. Regions most affected by land subsidence caused by groundwater extraction are usually productive agricultural regions, where water is mainly extracted for crop irrigation purposes. According to recent studies, 41% of worldwide affected aquifers withdraw the groundwater to supply the agricultural demands alone.

There is a consensus among scientists regarding Jakarta’s situation that the high-speed calculated land subsidence rates over-exploitation of groundwater mainly induces land subsidence in Jakarta, primarily attributable to groundwater extraction. This can be attributed to the absence of an alternative water source that makes two-thirds of Jakarta residents dependent on groundwater resources.

Indonesian municipal water supply serves on average only 25% of the population and 1% of the industrial needs, forcing the population and industries to rely on groundwater extraction as an alternate way to access water.

Subsidence is expected to be worse in densely populated areas located on compressible deposits. Cities such as Medan, Pekanbaru, Palembang, Jakarta, Depok, Bekasi, Bandung, Semarang, and Surabaya are likely to experience subsidence and the populated coastal areas of Java outside city centres.

Land Use Change (9%)

Areas of low lying land once occupied by water sources have been converted into urban housing causing major structural issues and increasing flash flooding and landslides. Land-use changes that contribute to land subsidence include:

Buildings construction for urbanisation purposes
Changing bare lands to irrigated lands
Water management infrastructure
Deforestation

Furthermore, rapid urbanisation and building development projects have reduced the soil’s capacity to absorb the torrential rain that The region experiences each year. The deforestation and land clearing used to make way for more high-rise apartments has made way for faster flowing water and increased the risk of flooding in many urban areas.

Jakarta has seen expansive growth and large scale apartments are a common sight.

What Are The Risks Associated With Land Subsidence?

A continuation of high subsidence rates is likely to put much of the densely populated coastal areas below relative sea level within a few decades.

Municipal authorities in Bangkok, Shanghai, and Tokyo have all struggled with land subsidence due to groundwater extraction. Land subsidence disrupts water supply and drainage networks and causes structural damage to roads and buildings.

Subsidence also increases the risks of seawalls being breached and exacerbates flooding. This is particularly the case in densely populated and low-lying delta cities across Asia, such as Jakarta.

Subsidence, in combination with sea-level rise, heavy rains (such as monsoon), or storms, aggravates inundation risk from the major rivers and widens the coastal areas affected by storm surges and tidal inundation. Therefore, the costs associated with subsidence are enormous, directly because of damages to buildings and infrastructures, and indirectly given the increase in flood risk and the threat to human life.

Some other potential risks associated with land subsidence are:

Increase in flooding potential caused by the decline of ground elevation
Changes in gradients of canals
The decline of ground elevation
Changes in quality parameters of groundwater
Increase in riverine or coastal flooding
Distortion of surface water infiltration mechanism
Exacerbation of sea-level rise in coastal regions
Threaten to the safety of urban infrastructures
Severe and costly damages to buildings, roads, and railway tracks
Malfunction of sewerage and drainage system
Variation of porosity and permeability due to soil deformation
Alteration of pore water characteristics
Changes in characteristics of seawater intrusion and artificial recharge
Changes in the sediment porosity and hydraulic conductivity of groundwater
Depletion of aquifer storage
Damages to pumping-wells
Decrease of aquifer capacity to store groundwater
Damage to historical heritage
Failure of the drainage system
Exposure and destruction of pipelines
Damages on buildings, roads, and bridges
Problems in foundation engineering practice
Cracking and collapsing of civil structures

Residents in Muara Baru live in one of the fastest sinking areas in Jakarta.

Climate Change

Changes in hydrological processes have occurred mainly over the last three decades, followed by the continuous increase in air temperature due to the concentration of greenhouse gases and fluctuations in precipitation and groundwater withdrawal.

Climate change affects the quantity and quality of groundwater by influencing the hydrological processes of the watershed. These processes are altered because of climate change (temperature, variable precipitations, extreme weather events and groundwater overexploitation).

Several studies report results about the impact of land-use change and climate change on land subsidence. These processes affect groundwater availability by affecting the living vegetation, responsible for water quality and nutrient regeneration.

The main processes are driven by climate change that enhance the consequences of land subsidence are:

Water cycle alteration (droughts increase groundwater demand)
Sea level rise (increases probability of coastal cities flooding)

Land subsidence in coastal cities can increase the risk of exposure to floods. These areas are already highly exposed to flooding risks due to sea-level rise caused by climate change. Moreover, droughts caused by the acceleration of the hydrological cycle are causing unprecedented groundwater overdrafts, which, as we have mentioned, is the leading cause of land subsidence.

Currently, global mean absolute sea-level rise is around 3 mm per year, and projections until 2100 based on Intergovernmental Panel on Climate Change (IPCC) scenarios expect a global mean absolute sea-level rise in the range of 3 - 10 mm per year. On the other hand, observed subsidence rates in coastal megacities are in the range of 6 - 100 mm per year, and projections until 2025 expect similar subsidence rates.

Land subsidence and sea-level rise to a phenomenon called “relative sea-level rise”. This happens when land sinks and, at the same time, the sea level rises. Global sea-level rise and land subsidence increase the risk of coastal flooding and thus contribute to shoreline retreat.

Floods In Jakarta Are Getting Worse

Recently recorded floods in Jakarta and the island of Java show just how devastating the impact has been on local residents:

In 2007, the worst floods in memory inundated about 70% of Jakarta, killing at least 57 people.
In 2012, floods displaced 2,430 people.
In 2013, many parts of Jakarta were inundated following heavy rain and killing at least 20 people and displacing around 33,502 people.
In 2015, the floods inundated Jakarta and caused an estimated loss of $234 million.
In 2016, around 8 sub-districts in South Jakarta and East Jakarta were flooded affecting 10,538 homes.
In 2020, rainfall was more than 3 times the average amount, there were 48 recorded deaths and multiple flood gates were deemed to be at an emergency level.
This year more than 200 neighbourhoods were directly affected in early 2021 by flooding in the area of Tangerang and Bekasi, 5 deaths were recorded, 4 of whom were children. Further severe flooding in Jakarta and West Java reportedly displaced over 30,000 people. The flooding was caused by high-intensity rainfall and the overflow of the Citarum River.

Jakarta is routinely flooded and if it continues as usual the residents will face irreversible damage.

Solutions Are Needed Now

We see that the city of Jakarta is facing numerous major challenges. Not only is it affected by rapid urbanisation and annual flooding but it is sinking faster than any other city on earth.

Many reports say that Jakarta is fighting an impossible fight. Unfortunately, little seems to be done about the city's infrastructure which is under increased pressure from an expanding population (an estimated 200,000 people move to Jakarta each year).

The residents still rely heavily on groundwater pumps, underground aquifers and boreholes to access their daily water supply and the water simply can not recover fast enough to meet demand.

Furthermore, we can’t ignore that many of the areas affected are the urban poor communities with people who rely on the ocean for a living such as fishermen. For decades. The widening lower class have been expected to deal with the problem leaving residents with no alternative but to continuously rebuild. In some ways, these coastal areas are being reclaimed by the sea whilst authorities are under pressure to come up with a solution.

What is truly needed is clean water. Next, regulation and then, of course, the enforcement of the regulations. Other cities, such as Tokyo and Venice have successfully developed regulations which have helped manage similar problems. For instance, Tokyo ceased groundwater extraction over a period of time in order to assist restoration levels, Bangkok implemented regulations for farmers requiring them to store rainwater which will return to the soil.

In Indonesia, researchers predict that the use of groundwater must cease entirely in the next 5 years in order to avoid serious consequences. This is by no means an easy task, authorities are facing significant challenges all stacked on top of each other with very little action taking place with many questioning if anything will ever happen. As Jakarta continues to sink, discussions of relocating the capital city are taking place.

North Jakarta has been the most impacted region for worsening land subsidence.

Relocating Jakarta

The relocation of the capital city is one of the most discussed and widely debated topics since it was announced in 2019. The big question is: will it solve Jakarta’s problems or simply move them elsewhere? Oh, and one more thing: how much will it cost?

Relocating the administrative capital from Jakarta to Borneo is estimated to cost Indonesia $32 billion dollars approximately 466 trillion rupiah. Critics have called it a huge waste of money that aims to shift the focus off of Indonesia’s more pressing problems.

If there is one group who is not convinced that the relocation plan is a good idea it's the environmentalists. Researchers say that shifting the city from one island to another will only make matters worse.

Jakarta is a polluted megacity sinking under the pressure of water pumping. However the next destination is Borneo, Asia’s biggest island, where the environment has been wracked by mines, plantations, oil spills, and forest fires to clear land for oil palms.
VOA News

Final Thoughts

Overall, the situation as it stands is complicated, to say the least. However, the development of an alternative water supply is one way the city could start to make a shift in the right direction.

With no quick fix, the residents of Jakarta, particularly those in the danger zone, are relying on the future actions of authorities to protect them; their homes and their livelihood.