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Jakarta Coastal Defence Strategy

Greater Jakarta (Jabodetabek) is sinking. Large quantities of groundwater are extracted by both industries and residents, resulting in subsidence of the city with approximately ten centimetres per year.

This process has been going on for many years. With an increasing population and urbanisation the government has to act on groundwater extraction. With 30 percent of the Greater Jakarta area already below sea level and an alternative water supply system many years away a strategic solution to protect North Jakarta from flooding by the sea is required.

Witteveen+Bos participates in a project team that assists in drawing up a strategic plan that on one side protects the city from flooding and on the other hand uses the required flood protection measures to solve a number of urbanisation problems such as traffic congestion, sanitation and water supply.

Sea defence

At the moment three different scenarios are being worked out. The first one is enhancement of the existing sea defence, which will cost little effort but will last for only a limited number of years. The second step provides in a new sea defence at the edge of new islands to be developed in the near future to increase the area of the city. Cooperation between the private sector and the government is foreseen.

Further improvement

This solution is expected to fulfil its duty up to 2025, maybe 2030. When needed, depending on the rate of subsidence in the future, a third scenario can be implemented, namely a sea¬wall to close off Jakarta Bay. This will guarantee absolute safety from flooding, but will be very expensive and requires measures to improve the water quality, but can also serve as starting point for further improvement of the city.

Triple-A method

The project is being carried out by means of the triple-A method to ensure stakeholder participation to create the required support from the entire community. The first step in the process is ‘Atlas’ that provides insight in the need to intervene. The second step is the ‘Agenda’ in which possible interventions are worked out. Both steps are followed by the ‘Aturan Main’ phase, that describes the process of implementation of the interventions. The project will result in a strategic plan and a roadmap for implementation by June 2011.