MANILA — Asia-Pacific coastlines face growing threats as sea levels rise and floods intensify, but investing in resilience could generate benefits up to 20 times greater than the cost, according to an Asian Development Bank (ADB) report.

Annual coastal flood damages in the Asia-Pacific region could increase more than sixfold by 2050 and nearly twentyfold by 2100 without adaptation, according to the Asia-Pacific Climate Report 2026: Coastal Risks on the Rise-Actions for a Resilient Future released on Wednesday.

Based on estimates across 30 coastal economies, the report estimates that annual flood damages could reach $172 billion to $199 billion by 2050 and $520 billion to $739 billion by 2100, compared with approximately $27 billion today.

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The report said keeping flood damages near today's levels would require an estimated $9 billion to $19 billion a year in coastal protection, an investment that could avoid $178 billion to $360 billion in flood damages each year.

According to ADB, over 400 million people in the region live within 10 kilometers of the sea. Coasts are hubs for ports and trade, as well as tourist and heritage spots. Without adequate adaptation measures, larger economies could face some of the highest economic losses in absolute terms, while relative impacts are particularly severe in atoll nations, where annual flood damage could reach 30 percent to 60 percent of GDP by 2100.

In major coastal cities such as Bangkok, Jakarta, Kolkata, and Mumbai, coastal floods that historically occurred once every 100 years could become annual events by the end of the century, said the report.