Indonesia: Development of Jakarta giant seawall crucial to prevent sea flooding

Callistasia Anggun Wijaya The Jakarta Post 6 Jun 16;

Flooding in Pantai Mutiara on the north coast of Jakarta on Friday has demonstrated the importance of building a seawall to enclose Jakarta Bay, the National Development Planning Ministry has said.

Jakarta Development Planning Board head Tuty Kusumawati said on Monday the construction of the seawall, which would be part of the National Capital Integrated Coastal Development ( NCICD ) program in North Jakarta, was crucial.

“It is urgent that the seawall be built, otherwise Jakarta will drown," Tuty said at City Hall.

She said the groundbreaking for phase A of the seawall would be held soon, adding that Jakarta was subsiding at an alarming rate.

"The level varies from 1 to 2 meters under the sea,” Tuty asserted.

Phase A of the seawall will be constructed in Pluit, North Jakarta, she said.

The existing height of the seawall is 3.7 meters, which will be extended by 1.1 meters, Tuti said.

"So the total height will be 4.8 meters and the length about 95 kilometers," she said.

The central government is conducting the project through Ciliwung-Cisadane Flood Control Office ( BBWSCC ), state-owned enterprises, regional-owned enterprises and private companies, Tuti said.

Currently, the Jakarta Environmental Management Agency ( BPLHD ) and the BBWSCC are reviewing and improving the environmental impact analysis ( Amdal ) on the construction in Pluit, she said.

Tuty added that the city would spend Rp 377 billion to build the dike along three rivers, namely the Kamal, Kaliadem and Blencong rivers.

The assistant to the governor for spatial planning and the environment, Oswar Muadzin Mungkasa, added that phase A of the seawall would not function optimally if groundwater usage was not limited.

“The construction of phase A will not be optimal if the ground keeps subsiding due to the uncontrolled usage of groundwater,” Oswar said.

The administration will also build green buildings, starting with the construction of the Daan Mogot low-cost apartments, he said.

The administration will also ensure that buildings construct water injection wells to mitigate flooding, Oswar said.

The groundbreaking ceremony for the mega-project was held in October 2014. The Netherlands and Indonesia have joined hands in the project. ( dan )

Land subsidence exacerbates flood risk in North Jakarta
Jakarta Post 6 Jun 16;

Land subsidence, soil erosion and high tide are only some of the problems northern Jakarta is facing.

The partial collapse of coastline embankments in Pantai Mutiara and Muara Angke, both in North Jakarta, over the weekend has raised alarm about the extend of those problems.

The incidents inundated hundreds of houses in both areas on Friday night and Saturday night respectively.

As of Sunday, floods in both areas have receded after the city administration installed water pumps and deployed workers from various institutions to tackle the breaches in the two embankments with sandbags.

Jakarta authorities blamed the incidents on the high tide and land erosion by seawater.

Jakarta Disaster Mitigation Agency ( BPBD ) spokesman Bambang Surya Putra said the high tide would likely last until Thursday.

He added that as long as phase A of the giant seawall project, also known as the National Capital Integrated Coastal Development ( NCICD ), to extend and repair the existing 90-kilometer seawall on the shores of the Jakarta Bay were not completed, northern parts of the city would remain under threat of inundation due to high tide.

Initiated in 2012, the NCICD aims to protect sinking Jakarta against flooding from the sea.

Under the NCICD master plan published in December 2014, the giant project requires two presidential regulations, one for the approval of the master plan and another for the formation of the development authority. Neither has been issued yet.

Commenting on the incident, Jakarta Governor Basuki “Ahok” Tjahaja Purnama said none of the embankments in northern Jakarta were sufficient to hold back seawater due to the rising sea level caused by global warming.

“Therefore, we need to build 3.8 meter-high embankments,” he said in an interview aired by a TV station on Saturday. He was referring to Phase A of the NCICD projects.

However, Bosman Batubara, a scholar on water science and governance who is pursuing his doctoral degree at the UNESCO-IHE institute for water education in Delft and the University of Amsterdam in the Netherlands, questioned Ahok’s statements on the rising sea level as the main cause behind the breach of the embankments and hence his suggestion to build higher embankments as a simple way out.

“The fact is that the extent of land subsidence in Jakarta is greater than the rise of the sea level,” he told The Jakarta Post on Sunday.

He added that the rising sea level caused by global warming in Jakarta was less than 1 centimeter a year, while land subsidence amounted to 10 cm per year.

Currently about 40 percent of the Jakarta area is below sea level; land subsidence is mainly caused by the heavy load of buildings on the land.

Research by the Jakarta Mining Agency from 2007 showed that 80 percent of the city’s land subsidence was caused by building constructions, 17 percent by groundwater exploitation and 3 percent by natural causes.

A 2008-2009 seismic study by three geophysics experts, Suhayat Minardi ( Mataram University, West Nusa Tenggara ), Darharta Dahrin ( Bandung Institute of Technology, West Java ) and Mahmud Yusuf ( Meteorology, Climatology and Geophysics Agency ) from showed that land subsidence in the city amounted to about 15 cm per year.

“Therefore, Ahok’s solution to build a giant seawall as an answer to protect North Jakarta against floods caused by high tide is irrelevant. The construction of such a seawall, on the contrary, will accelerate land subsidence, hence increasing the risk of floods,” Bosman claimed.

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