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The threat of oods

The more than 10 million inhabitants of the Jakarta metropolitan area (Indonesia) are

familiar with ooding in the rainy season. Sedimentaon combined with increased dis-

charges create high water levels and the occasional ood in the 13 rivers and canals ow-

ing through the at, low lying urban delta. Street ooding is a more common event as the

city struggles to keep the urban drainage system in pace with urbanizaon. However inFebruary 2007, North Jakarta was hit by a dierent ood. A high de overtopped the sea

wall in Pluit, a low-income sea side neighborhood in North Jakarta and sea water was

rushing through the streets creang high waters up to 1.5 meters for several days.

Alarming Rate of Soil Subsidence

This ooding from the sea conrmed what some researchers already had been warning

for: North Jakarta is subsiding at a staggering speed of 7.5 cenmeters per year (some

parts up to 14 cenmeters per year) and large parts of the city will be under sea level

within the next 10 years. If the current trend persists sea level could reach up to 7 meters

above street level in 2080. In the years following the 2007 ood huge eorts were made

to monitor and research subsidence and, at the same me, to build a sea wall high

enough to withstand the sea water for a few years. Indonesia in close cooperaon with

The Netherlands, Japan and Korea executed several research projects, constructed thesea wall and increased the pumping capacity to keep the most endangered low lying are-

as dry.

Jakarta Coastal Defense Strategy

However, the speed and magnitude of the land subsidence is such that the need for a

comprehensive strategy became clear soon. The Jakarta Coastal Defense Strategy project

(JCDS) provided the blueprint for this strategy. The key approach would be that 3 lines of

sea defenses would be created over a period of 20-30 years. Each subsequent line would

be constructed more seawards, the last line would be a sea wall in the Bay of Jakarta,

closing of the bay and creang a large fresh water lagoon. This sea wall (also known as

Giant Sea Wall or Outer Sea Wall) would not only keep out the sea water, but also would

be used to keep the 13 rivers free owing, thus lowering the risk of river oods in the city.

This was necessary as the rivers slowly lost the ability to ow under gravity, due to the

rising sea level. For this, the water in the closed o lagoon would be lowered by pumping

to a level that allows free river ow. The lagoon would become a future fresh water

source for the drinking water supply of Jakarta.

NATIONAL CAPITAL INTEGRATED COASTAL DEVELOPMENTNATIONAL CAPITAL INTEGRATED COASTAL DEVELOPMENTNATIONAL CAPITAL INTEGRATED COASTAL DEVELOPMENT

CHANGING THREAT INTO OPPORTUNITY

INDONESIAINDONESIAINDONESIA

Outer Sea Wall Concept

Bird Eye View

Java Island

Program area

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Towards Integrated Coastal Development: NCICD

The JCDS project was followed up by the Naonal Capital Integrated Coastal Development

project (NCICD). The name of this project reects two developments. Firstly, the naonal im-

portance of the program which stretches beyond the city limits of Jakarta: measures in adja-

cent and upstream areas are part of the strategy. Secondly, the integrated character of the

development, where technical, socio-economic and spaal development aspects have to go

hand in hand.

The NCICD-project started in January 2013 and will produce a Master Plan together with an

implemenng organizaon model and an investment strategy within 2 years me. The pro-

ject organizaon reects the naonal importance of the NCICD project: nearly all Indonesian

ministries and Jakarta City administrave bodies are involved under the guidance of the Coor-

dinang Ministry of Economic Aairs. The plan process is supported by leading Indonesian

experts, both private and academic. The government of The Netherlands provides technical

assistance for the Planning phase.

The NCICD strategy consists of a broad set of measures, starng with addressing the driving

force behind the sea level rise: the land subsidence. Together with this, two ood defense

lines will be prepared: strengthening and raising the exisng sea wall, to provide short term

protecon, and an oshore Outer Sea Wall providing long term protecon. These ood de-

fenses will be fully integrated in the urban and socio -economic development of greater Jakar-

ta, seeking nancing opportunies and socio-economic synergy.

Acceleraon

The strategy has many obvious implicaons (raising dikes and sea walls), but also several not

so obvious, like the urgent need for improved piped water supply and the acceleraon of wa-

ter sanitaon. Plans to provide piped water supply already have been approved and construc-

on is scheduled to start in 2015. However, it is not certain to what extend the subsidence is

caused by ground water extracon and (residual or permanent) land subsidence must be tak-

en into account.

Acceleraon of the water sanitaon in Jakarta is also a key factor in the project. Water quality

in the rivers and canals is very poor due to lack of proper sanitaon and sewerage. Closing o

the Bay of Jakarta in these circumstances would lead to a giant sepc tank or Black Lagoon.

The governments of Indonesia and Japan are currently cooperang to improve the sanitaon,

but the construcon of an Outer Sea Wall in the coming decade, necessitates the acceleraon

of the water sanitaon program. The water quality must improved by 75% before the lagoon

can be closed o.

Complexity

The NCICD program is complex in all aspects. The outer sea wall would be 50 km long, in wa-

ters of 16 meters depth, and rising 7 meters above sea level. 160 million m3of sand and 33

million tons of rock are needed for construcon. In order to pump out the fresh water from

the city and rivers, a drainage pumping capacity of 600-900 m3/second needs to be installed,

operated and maintained. This is 50-100% larger than the largest pumping staon in the

world. Major related issues will have to be addressed, such as the future of the shing com-

munies and shing ports, the main port Tanjung Priok (Indonesias largest port), the three

power staons on the current coastline, reselement of thousands of households on the river

embankments, and the threatening loss of protected mangrove sites. Also matching the huge

nancial upfront investments with the future returns from land reclamaons and property

developments is a major challenge.

Nevertheless, Indonesia needs to rise to this enormous challenge in order to protect the Ja-

karta metropolitan area against permanent ooding. Despite the huge costs, the far -reaching

implicaons, decision makers already have commied themselves to the project and the

strategy, understanding that there is no other alternave but to abandon North Jakarta.

NCICD

PROGRAM MANAGEMENT

UNIT OFFICE

Menara Ravindo 5th Floor

Jl. Kebon Sirih Kav.75

Jakarta 10340

Indonesia

Phone : +6221 3192 4863

Fax : +6221 3192 4878