Prabowo's wall against Indonesian coastal erosion

The president has decided to build a 700-kilometre-long barrage to stop the sea advancing and causing cities to sink. But there are strong doubts about the feasibility and effectiveness of this colossal work

Jakarta (AsiaNews) - The northern coast of Java, including the capital area of Jakarta, is marked by increasing subsidence and erosion. Entire areas of the coastline from the western province of Banten to the eastern region of Gresik are experiencing annual subsidence of even more than 20 centimetres, and in the last two decades have seen the sea push up to two kilometres into the mainland.

An unstoppable advance that has submerged numerous villages and covered or salinised vast stretches of agricultural land, forcing the population to seek relocation elsewhere, both for security and economic reasons. Not that these phenomena are confined to the north coast of the island, which alone is home to some 160 million inhabitants, 56% of the Indonesian population, and where the densely populated areas of Jakarta, Pekalongan and Semarang are among the hardest hit by the subsidence; they also affect the east coast of Sumatra and southern Borneo with less intensity. A major cause, but not the only one, is the poor consistency of the sedimentary soils.

A situation that has so far also highlighted the diversity of possibilities and action between metropolitan areas, which have greater economic and technical possibilities, and rural areas, which are in fact depopulating as the only alternative to the advancing waters. 'Unfortunately,' points out Heri Andreas, an expert at the Bandung Institute of Technology, 'in villages with small populations, local governments have a tendency to favour relocation over the construction of expensive coastal barriers.

That is why, while the project to move the administrative capital from Java to the east coast of Borneo under the name of Nusantara is proceeding slowly, the Prabowo administration has decided to build a 700-kilometre wall to defend the fertile and productive coastal regions under threat. A colossal work that already now, a few weeks after the start of the project, raises doubts and concerns. If in fact the president has indicated how the work takes into account Indonesia's commitment to self-sufficiency in several products, including rice, the scale of the project, the long timeframe and the financial constraints, risk making it useless.

Like Jakarta, which could be virtually swallowed by the sea by mid-century, and the large industrial centre of Pekalongan, which risks being 90 per cent submerged within a decade, regions that are now densely populated would be de facto depopulated before then.

It is unclear whether the sea wall project will also incorporate realisations that are in the process of being completed. For instance, the Pekalongan barrage, which cost USD 73 million and will be completed within the year. Or the large 27-kilometre toll road linking Semarang to Demak, costing USD 918 million, also planned as a tidal retaining wall to be completed in 2027.