Annual coastal flood damage in Asia and the Pacific could reach up to $739 billion by 2100 from around $27 billion at present unless countries invest in adaptation measures, according to a new report by the Asian Development Bank (ADB).
The report, Asia-Pacific Climate Report 2026: Coastal Risks on the Rise—Actions for a Resilient Future, estimates that annual flood damage across 30 coastal economies could rise to $172 billion to $199 billion by 2050 and $520 billion to $739 billion by 2100 without adequate adaptation.
However, investing $9 billion to $19 billion annually in coastal protection could keep flood damage close to current levels and avert an estimated $178 billion to $360 billion in losses each year, the report says.
Released on Wednesday, the report warned that the region's coastlines, which generate around $7 trillion in annual economic output, are facing growing threats from rising sea levels and intensifying climate-related hazards.
"Coasts are the overlooked engine-room of Asia and the Pacific's growth but are retreating in the face of rising seas and escalating hazards," said Yevgeniy Zhukov, director general of ADB's Climate Change and Sustainable Development Department.
"We are at a turning point and must act now with long-term, adaptive, and risk-informed solutions to create resilient coasts that keep people safe and economies running," he said.
More than 400 million people in the region, or over one in 10 people in ADB's developing member economies with coastlines, live within 10 kilometres of the sea.
Coastal areas support ports, trade, tourism and heritage sites, making them vital to regional economies. The report warns that large economies could face some of the highest losses in absolute terms, while the relative impact could be far more severe for small atoll nations.
Under a high-emissions scenario, annual flood damage in these island nations could amount to 30% to 60% of gross domestic product by 2100.
Major coastal cities, including Bangkok, Jakarta, Kolkata and Mumbai, could also face a sharp increase in flooding. Floods that historically occurred once every 100 years could become annual events in these cities by the end of the century.
Disruptions to ports pose another major economic risk, with around $40 billion to $45 billion at stake annually across the region.
To address these threats, the ADB report calls on governments to integrate adaptive planning into development decisions, strengthen institutions and governance, mobilise financing, and ensure sustained implementation and local ownership.
It recommends linking immediate measures with long-term development goals while keeping policies flexible enough to respond to changing climate risks.
International adaptation finance for coastal economies in Asia and the Pacific has increased from around $5 billion in 2015 to an average of $11.4 billion annually in 2022 and 2023.
Despite the increase, a substantial financing gap remains, the report says.
Public finance will remain the foundation of coastal resilience investments, but governments will need to expand fiscal space and mobilise additional public, private and concessional funding to meet long-term needs.
The ADB, founded in 1966, is a multilateral development bank supporting sustainable and inclusive growth across Asia and the Pacific. It is owned by 69 members, including 50 from the region.