Experts warn Jakarta Bay project may up flood risk

Adianto P Simamora, The Jakarta Post, Jakarta

The construction of the North Flood Canal in Jakarta could be one way of reducing the flood risk in the city.

But the ongoing land reclamation project — which will modify a 32-kilometer stretch of the city’s northern coastline, extending it seaward — will render it ineffective, environmentalists warned Wednesday.

State Minister for the Environment Rachmat Witoelar said the reclamation of the seabed would obstruct the movement of water back toward the sea.

He suggested the Jakarta administration reconsider its decision to carry out its own environmental impact analysis for the project.

“The administration must involve the central government in the process because the project will also affect the environment in neighboring provinces.”

The controversial reclamation project would add about 2,700 hectares to the city. The land would be designated for industrial parks, hotels, office buildings and upscale accommodation for up to 1.19 million residents.

Governor Sutiyoso, in his appearance on Metro TV during the flood early this month, said the reclamation project would be one way of preventing floods caused by high tides.

Forty percent of the city is situated below sea level.

“About 72 percent of the world’s coastal cities have reclaimed part of their seabeds. It is an age-old issue. We will monitor the project all the way and stop it if the land reclamation is damaging the environment,” Sutiyoso said.

An expert from the Bandung Institute of Technology (ITB), Atika Lubis, said the construction of infrastructure near the cost would increase the flood risk in the city.

“The reclamation project will, of course, jeopardize the success of the North Flood Canal. It will reduce the rate at which surface water reaches the sea, thus causing floods.”

She said the administration needed to be aware of the slow permeability rate of the city’s land.

“The reforestation of areas of North Jakarta, for example, will not contribute much to flood prevention efforts because clay does not hold water very well,” she said.

“Therefore, the construction of apartments, hotels or other infrastructure along the coastline or in delta areas will further hold up the flow of water into the sea,” she said.

Armi Susandi, a coordinator at the Indonesia Association of Geophysicists (HAGI), warned more areas of Jakarta would be prone to flooding in the future due to global warming.

“The water level in Jakarta Bay will rise by 57 millimeters a year, while the land will subside by 80 mm a year,” he said.

Armi, who is also an ITB meteorologist, said many areas of Cilincing, Koja, Tanjung Priok, Pademangan and Penjaringan in North Jakarta would be under water by 2050.

“By our estimations, some 160 square kilometers of Jakarta will be swamped by 2050,” he said.

Global warming, the gradual increase in the earth’s surface temperature, is thought to be caused by human activity.

Meanwhile, ITB geologist Lambok Hutasoit said the presence of buildings higher than six stories in Central Jakarta had caused the land to sink by between 22 and 75 cm in two years.

“People are blaming land subsidence on the exploitation of groundwater. But it only comprises 17 percent of the problem,” he said.

Lambok proposed the construction of giant groundwater tunnels to prevent floods in the rainy season and water shortages in the dry season.

“We can apply the underground tunnel system developed in Chicago, where a 200-km tunnel was built to store water,” said Lambok, who is also an expert at the city’s mining agency.