Dutch companies plan flood protection for Jakarta

Indonesia secured its independence after the second world war following three and a half centuries of Dutch colonialism. There exists therefore an enduring link between the two countries, and given the vast experience and skills of the Netherlands in the management of water, including flood defences, development of the plan was a natural move. The minister’s visit included presentation of the National Capital Integrated Coastal Development Masterplan, a project that has been developed over the past two years by Witteveen+Bos along with Grontmij and a number of other parties. Problems affecting Jakarta and addressed by the masterplan include: flooding, soil subsidence, an inadequate water supply system and poor water quality. Solving such problems of course goes beyond just producing action plans and the document combines proposed solutions with an analysis of expected economic and social benefits.

Public tenders for producing the plan were called for in 2012 and consultancy and engineering services provider Witteveen+Bos sought collaboration with other parties on the project. The result was a consortium including Grontmij, KuiperCompagnons, Deltares, Ecorys and Triple-A. The subsequent proposal involves a two-phase approach: flood protection in the short term, and sustainable urban development in the longer term. The consortium was subsequently awarded the contract by the Dutch Government (Partners for Water).

GROUNDWATER EXTRACTION

Inhabitants of Jakarta are no strangers to the natural phenomenon of flooding, events being recorded virtually on an annual basis. In February this year, around 300,000 residents were left homeless with dozens of casualties also being reported. Water from surrounding areas flows into the city but cannot be drained off fast enough. Soil subsidence due to groundwater extraction is reported to be a major cause of the flooding problem, in some areas as much as 17cm of soil subsidence being experienced each year. Subsidence is not the only cause of Jakarta’s water problems however, no fewer than 13 rivers flow into Jakarta Bay from the volcanic hinterland, the problem further exacerbated through growing urbanisation upstream.

Geographical similarities between Jakarta and the Netherlands are reflected in estimates that by 2030, some 80% of the former will be located below sea level. The metropolis itself is densely populated, room for flood protection measures becoming increasingly limited. The masterplan therefore calls for offshore flood protection measures in Jakarta Bay, the only area still offering sufficient room for such measures. As a temporary measure the coast needs to be reinforced with a new enclosure dam proposed to be built in the bay. It is suggested the dam can be financed through simultaneous large-scale land reclamation. The plans also call for a new waterfront to be included shaped like the mythical Garuda bird, the national symbol of Indonesia. Realisation of this element of the plan would require massive investment and be one of the world’s largest hydraulic engineering projects.

The plan has been assessed for its financial, technical, socio-economic and ecological feasibility with cost of implementing the various measures currently estimated at US$10-40bn. Rapid construction of a complete enclosure dam between the eastern and western end of Jakarta Bay is logistically unfeasible, there being insufficient dredging vessels in the entire world to supply enough soil. The volume needed to construct the western section is comparable to that of Maasvlakte 2 at Rotterdam. Various factors will determine if and how the plan is implemented including growth of the Indonesian economy, not to mention presidential elections. The masterplan therefore involves a phased plan to tackle the problems.