The rainy season comes. Not only floods threaten Jakarta, but also threatens the land subsidence. Slowly but surely, Jakarta is also going to drown. Spooky!
Lately more and more areas of subsidence Jakarta. Not long ago, Jalan Raya Pluit Beautiful, right in front of Mega Mall Pluit, North Jakarta, get down. Subsidence that occurred in September 2011 it formed a hole about 1 meter in diameter with a depth of nearly 2 meters.
Previously, the end of July 2011 the land in the region Rawajati Village, District Pancoran, South Jakarta sinkhole. As a result, 21 houses in RW 4 Village Rawajati heavily damaged. In fact, the barrier between citizens and City Apartamen Kalibata also a six-foot sinkhole.
The year before, 16 September 2010 at 3:15 pm, RE Martadinata Highway that connects the Port of Tanjung Priok, North Jakarta to the direction the City was gone. Which coincides with the river road that collapsed as deep as 7 meters with a length of about 103 meters of rubble. Cause amblasnya land on the road is expected due to sea erosion.
In 2008, a number of buildings in Jakarta also began sinkhole. Call it building and building Sarinah Agency for the Assessment and Absorption Technology (BPPT) on Jalan MH Thamrin.
MH Thamrin-Sudirman area does include areas expected Walhi Jakarta will sinkhole. Besides other vulnerable areas are triangles Brass and Sudirman Central Bussines District (SCBD).
Amblesnya land around MH Thamrin was due to the increased intensity of development of the property in the business district since 2007. Tilted or cracked buildings in Jakarta due to unconsolidated soil structure so that there is a cavity.
“This is due to unbalanced circulation of groundwater, soil water is greater than that sucked rainwater is absorbed into the ground,” said Executive Director of Jakarta Walhi Ubaidillah to seconds +.
So far a number of related agencies do not have the same data the precise rate of land subsidence in Jakarta. But clearly every year more and more worried because of subsidence data continues to increase.
Walhi Jakarta mention the average subsidence of land reaching 10 cm per year. Of all the areas that exist, the point most vulnerable to inundation and land subsidence in the area of North Jakarta as many as 26 locations.
Data Walhi Jakarta, local land land (land subsidence) from the period 1982-1997 to reach 20 cm in 15 years. 1997-2007 period reached 18-26 cm in 10 years.
While the Consortium data Jakarta Coastal Defence Strategy (JCDS) in the period 1974 to 1990 mention land subsidence in the northern Jakarta about 3-5 cm per year. Several recent studies and observations show a larger number. In North Jakarta indicated land subsidence occurred about 5-10 cm per year.
In the period 1974-2010 there has been a decrease in surface soil in the Jakarta area up to 4.1 meters. This is particularly true in the area of Muara Baru, Cilincing, North Jakarta.
A similar decline occurred in several other areas, such as in the West Cengkareng as high as 2.5 meters, 1.97 meters Daan Mogot, Ancol 1.88 meters (point monitored in Ancol tourist area), Cempaka Mas 1.5 meters, Cikini 0, 80 meters, 0.25 meters and Cibubur.
JCDS also mentioned there are 7 bridges ambles, the bridge Kamal Muara, Mango Two, Ancol, Pluit, Pantai Mutiara, Gunung Sahari and the Big Mango.
“Often the difference is caused, due to differences in methods of observation, Bench Mark (BM) and referred to the character of the observed points as if it was just dumped or a highway and so forth,” explained Sawarendro, a consultant from the Netherlands who are members of JCDS.
Chairman of the Indonesian Geologists Association (IAGI) Lambok M Hutasoit confirmed the existence of land subsidence in Jakarta, which can reach tens of centimeters per year. Only, he argues, the case of RE Martadinta amblesnya Road in North Jakarta is not automatically referred to as land subsidence.
“Because it happened quickly, unlike land subsidence is quite slow. the sinking road was likely caused by other factors such as erosion of the river or ocean wave erosion,” explained Associate Professor of Hydrogeology Field Institute of Technology Bandung (ITB) is to seconds +.
Recognized Lambok, IAG has not until now have data that can be verified concerning land subsidence in Jakarta. “We have not memperivikasi data about it. However, based on the measurement of geodetic experts, land subsidence occurred in the area north of Jakarta, which is around Cengkareng, Kemayoran, and Palm d’Ivoire, with a maximum subsidence has reached 2 meters,” said Lambok.
Coordinating Agency for Surveys and Mapping (Bakorsutanal) also recognizes a decrease in surface soil in Jakarta. The existence of high-data obtained from careful observation of nature and the GPS flat made during the study, showed decline in one region of the surface soil varies spatially and temporally.
1982-1991 data from the largest decline occurred in the surface soil at the rate of decline in Cengkareng location of 8.5 cm per year. In 1991 – 1997 occurred at a rate of decline Kwitang 14.8 cm per year, from 1997 to 1999 occurred in Daan Mogot at a rate of 31.9 cm per year decrease.
From the height data of GPS observations in December 1997 – June 1999, the biggest decline occurred in Pantai Indah Kapuk a rate decrease 11.5 cm per year. June 1999-June 2000, still in Pantai Indah Kapuk at a rate of 10.4 cm per year decrease. June 2000-June 2001 occurred in Daan Mogot with the rate falling 34.2 cm per year, in June 2001-October 2001 occurred in Rukindo-Ancol with a rate of 23.7 cm per year decrease.
Land subsidence is a serious if not treated would make Jakarta sinks. Executive Director of the Indonesia Water Institute Firdaus Ali predicts Jakarta will sink in the near future, namely in 2012. “The city will get down or drowned technical language by 2012,” said Firdaus.