Reference source: Indonesian Institute of Technology Bandung (ITB)
In 2018, the Indonesian Institute of Technology Bandung (ITB) published a research survey. According to this survey, the ground in North Jakarta has subsided by 2.5 meters in the past 10 years, which is more than twice the rate of subsidence in coastal cities around the world.
However, the subsidence problem is not unique to North Jakarta. In West Jakarta, the average subsidence is 15 cm per year, 10 cm per year in the east, 2 cm in the central part, and 1 cm in the south. On an overall scale, about 40% of Jakarta is now below sea level. Furthermore, according to model estimates, about 95% of the northern coastal land will be submerged by seawater by 2050. Under the influence of global warming, coastal port cities in all countries will face the possible impact of sea level rise.
For the Jakarta area, its tap water system is not comprehensive enough. Only one-third of Jakarta citizens have access to tap water, and 65% of Jakarta residents rely on pumping groundwater for drinking or daily water use. Not only homes, but many businesses, restaurants, and shopping centers also use free groundwater. Professor Heri Andreas, currently working in the Department of Geodetic Engineering, ITB’s Faculty of Earth Science and Technology, said: "Groundwater can be used by anyone, whether it is for domestic or industrial use. But the biggest problem in Jakarta is that the urban planning is not perfect, government officials have problems in implementation, and the government has not done a good job of supervision, which makes the people over-pump groundwater."
Therefore, on February 28, 2022, our team also followed the ITB team to the Muara Baru and Ancol coastal subsidence measurement and observation stations in North Jakarta, and learned about the current problems of coastal subsidence and the local government's countermeasures. At first, we visited PPS Nizam Zachman Jakarta in Muara Baru, Jakarta, to investigate the local subsidence measurement observation stations and facilities, and to see the current status of coastal embankments in coastal areas. Since the Indonesian government did not enforce regulations on the use of groundwater, it promoted the "National Capital Coastal Integration Development Plan" as a countermeasure to prevent Jakarta from being submerged. In addition to lengthening the coastal embankment, this plan is mainly to build a huge Jakarta sea wall of about 30 kilometers off the coast of Jakarta Bay. However, while sea embankment is one of the main ways to protect the coastal communities in North Jakarta from salt water intrusion, it is not a long-term solution.
Our team also went to the strata subsidence measurement and observation station in Ancol area together with ITB members to visit the strata subsidence monitoring and measurement equipment. Professor Heri Andreas introduced that in the past, the ITB used tidal data collection and processing, tidal instruments, measuring stations, and global navigation satellite system measurement equipment to collect data on stratum subsidence and sea level rise. Professor Heri Andreas believes that coastal flooding on the coast of Jakarta has become an important issue at present. If the disaster occurs, the economic consequences will reach hundreds of trillions of Indonesian rupiah. Therefore, adaptation and mitigation measures must be taken.
However, the current policy of the government to promote the construction of seawalls can only be used as a short-term measure, because the dams are gradually sinking, and in the end, the height of the dykes still needs to be continuously raised to prevent them from being submerged. An effective strategy should be that the government must popularize tap water supply as soon as possible, and legislate to control the extraction of deep groundwater, prepare alternative water sources in advance or stop exploiting groundwater, that is, conduct comprehensive resource management plans for land and water sources passing through the basin to obtain alternative water sources. At the same time, it is hoped that the government will pay more attention to the monitoring and early warning of strata subsidence and sea level rise, so as to achieve mitigation and adjustment strategies
