JAVA’S NORTH COAST — Indonesia plans to begin construction in September 2026 of a sea wall more than 500 kilometers long along Java's north coast to defend the region from rising sea levels. The project, which includes a lagoon behind the wall, is expected to cost at least US$80 billion and take decades to complete.

The sea wall will be overseen by several government agencies and subject to scrutiny by Indonesia's Corruption Commission (KPK). Funding is planned to come from provincial and national budgets and from public-private partnerships with countries such as the United Arab Emirates.

Flood risk on Java's north coast is driven by land subsidence and land use. Subsidence in Java is caused by factors including excessive and unregulated groundwater extraction, building load, mangrove deforestation, seawall construction and increases in soil moisture. Indonesia has historically managed flooding by building infrastructure such as canals and dykes, reclaiming land, and deepening or straightening rivers. These flood management measures have often exacerbated flooding problems or served only as stopgap steps before sea-level rise overtakes subsiding land.

Indonesian civil society groups say the sea wall could prompt more sand mining, degrade mangroves and affect the livelihoods of fishing communities. The groups fear the project will worsen existing ecological destruction associated with industrialization. Indonesian media and academics are pressing for a strategy that includes consultation with affected communities, integrated coastal management, wastewater upgrades and river cleanup. Without environmental reforms, a future lagoon behind the sea wall could become a low-oxygen moat.

Recent modeling suggests offshore structures can reduce storm surge heights in some locations, but outcomes vary by location and the local underwater environment. Recent research also shows that different levels of government communication about flooding problems change how people understand these messages, potentially undermining efforts to reduce groundwater extraction. Flood works that do not address the causes of subsidence can redistribute harm, entrench inequity and affect Indonesia's food security.

Coastal adaptation projects have historically been sites of political argument and corruption. How Jakarta manages the sea wall project will shape regional security for Australia, whose Department of Foreign Affairs and Trade has historically collaborated with Indonesia's BAPPENAS on infrastructure such as water projects. Indonesia is affected by climate change, often through severe and regular floods.