The city of Jakarta is constructing a giant sea wall, known as the Jakarta Coastal Defense Strategy (JCDS), to protect low-lying regions as sea levels rise and land subsides due to heavy extraction of groundwater from the delta soil.

A 2009 study by Bandung Institute of Technology (ITB) climatologist Armi Susandi predicted that a quarter of Jakarta will be submerged by 2050 because of continually rising sea levels, which he said was a by-product of global warming.

The subsidence rate, which is also a response of delta soils to heavy construction, is estimated at between 10 and 20 centimeters per year; however, the ground level of some parts of North Jakarta already been reduced by 4.1 meters.

A new 1,500 ha city, and rapid transit lines, will be constructed along and within the wall, which will surround 10,000 ha in total, be 60 km long and extend 8 km out from the shore. The projected completion date of 2020 is now five years earlier than anticipated because the city has decided to skip the second phase of construction, which consisted of building dikes, pumps, and retention ponds. Since these features would stave off rising sea levels for only ten years, it was decided that the city could better use its resources by moving ahead to the third phase of construction.

The third phase consists of building the giant seawall along Jakarta Bay and includes retention ponds and pumps designed to remove 500 cubic meters of water per second.

According to the JCDS, approximately 40% of the land in Jakarta is below sea level and North Jakarta is expected to be below sea level within 10 years. The JCDS is currently completing a feasibility study for the Great Wall project with expert and financial support from the Dutch government, which has taken a similar approach to protect the Netherlands.

In the aftermath of Hurricane Sandy, which saw high tides, warm ocean water and 130 km/hr winds create a record nine meter-high storm surge, it will be crucial for the JCDS to ensure the sea wall is high enough to withstand the extraordinary conditions we may begin to see as climate change progresses.

ACT is part of the international Coastal Cities at Risk (CCaR) network, which seeks to explore solutions to climate change’s impacts on coastal megacities.