Three in four Bangkok residents now live on a floodplain

Claim types Estimate · Interpretation

European Commission, Joint Research Centre, GHS Urban Centre Database 2025 (GHS-UCDB R2024A), version 1.2 (May 2026), CC BY 4.0; doi:10.2905/1a338be6-7eaf-480c-9664-3a8ade88cbcd. Read from the JRC download server on 4 Nov 2026: theme EXPOSURE field EX_100_POP (people exposed to floods, 100-year return period: GHS-POP R2023A population inside the urban centre, masked by the JRC/CEMS-GloFAS 100-year flood hazard map, Baugh et al. 2024) and theme GHSL field GH_POP_TOT (population of the urban centre). Shares are progrss calculations (EX_100_POP / GH_POP_TOT). People in the flood zone / population, 1975 → 2025: Suzhou–Wuxi (GHSL 'Suzhou', includes Wuxi) 2,626,048 / 2,916,841 → 10,743,159 / 11,540,430; Shanghai 5,251,249 / 6,388,290 → 25,261,369 / 30,678,616; Bangkok 2,666,966 / 4,361,118 → 14,192,595 / 19,048,032; Dhaka 5,822,969 / 8,915,061 → 21,175,723 / 37,307,160; Shantou (includes Jieyang, Chaozhou) 1,084,292 / 2,806,300 → 5,148,446 / 10,579,303; Guangzhou–Shenzhen (GHSL urban centre 'Guangzhou', the whole Pearl River Delta) 1,742,118 / 4,454,995 → 16,908,161 / 42,987,704; Delhi (GHSL 'New Delhi') 1,371,076 / 6,779,237 → 9,204,773 / 31,422,508; Kolkata 3,091,672 / 12,497,153 → 6,746,055 / 23,314,585; Cairo 1,349,257 / 8,406,070 → 7,134,008 / 25,230,325; Ho Chi Minh City 615,178 / 3,059,219 → 4,025,110 / 14,557,830; Manila 2,775,428 / 9,582,901 → 5,621,804 / 25,921,189; Tokyo 4,974,843 / 24,708,446 → 6,384,308 / 33,155,907. Rows: the 12 urban centres of 10 million or more people in 2025 with the most residents inside the flood zone (13th: Buenos Aires, 2.9 million). Bangkok's rise (+13.3 points) is the largest of all 21 urban centres of 10 million+ with at least 11% of residents in the zone. Urban centres follow contiguous built-up land with the boundary fixed at its 2025 extent for every year, so they can be larger than the city itself (Cairo includes Giza and New Cairo). Important caveats: the JRC fact sheet describes one 100-year flood hazard map (JRC/CEMS-GloFAS, Baugh et al. 2024) with no year, so the same map applies to every year. The JRC's global flood hazard maps do not include flood defences or control works (Riedel et al. 2024, Geoscientific Model Development 17:5291, on the JRC maps that Baugh et al. update): dikes, dams and pumps are ignored. Because the map is fixed, a rising share means more of the city's people live in the zone, not that floods got worse. Where big dams control the river (the Nile at Cairo, behind the Aswan High Dam), actual risk is much lower than the map suggests. Population figures are JRC model-based estimates; Bangkok's 2025 population (19.0 million) is close to UN World Urbanization Prospects 2025 (18.2 million). Takeaway 3 is an interpretation.

Published 4 Nov 2026