Colombo's Ramsar-Accredited Wetlands — Flood Buffering Under the Metro Colombo Programme (Sri Lanka)

Colombo's low-lying marshes historically buffered the city against monsoon flooding, but decades of infilling for construction shrank them. FloodList reports that by 2018 only about 17% of Colombo's territory remained unencroached wetland (roughly 20 km2 combined), yet this remnant could still retain close to 40% of the area's annual rainfall — a storage capacity the Sri Lanka Land Reclamation and Development Corporation likens to more than 27,000 Olympic-sized swimming pools.

Sri Lanka adopted the Colombo Wetland Management Strategy in 2016 and folded wetland protection into the World Bank-supported Metro Colombo Urban Development Project (about $321 million, roughly two-thirds Bank-financed), which restored former dumping grounds into public wetland parks — including Diyasaru Park (about 24 hectares) near the parliament complex and the neighbouring Beddagana park — that double as flood-storage basins and recreational green space, with at least 10 further sites identified for future restoration.

On 25 October 2018, at the Ramsar Convention's COP13 in Dubai, Colombo became the first capital city in Asia accredited as an International Wetland City, formally recognising the wetlands' role in flood control alongside urban planning safeguards against further encroachment. FloodList's analysis, citing city planning figures, estimates that losing the remaining wetlands entirely could cut Colombo's roughly $53 billion annual metropolitan GDP by about 1% through increased flood damage, against a projected wetland-tourism potential of about $12.7 million a year. A 2026 Frontiers in Water study of water-level fluctuations in the Colombo wetland complex provides peer-reviewed hydrological support for their flood-buffering role.

Coverage gaps remain: no source found gives an independently verified species count or biodiversity monitoring programme for the wetland network as a whole, and continued encroachment pressure is repeatedly flagged as an ongoing risk to the strategy's long-term durability.

Read the full analysis: https://www.iwmi.org/news/colombo-wetlands-and-the-built-environment/