Colombo's Urban Wetlands — Avoided-Cost Flood Mitigation for a Ramsar Wetland City (Sri Lanka)

Colombo sits within a roughly 20 km² wetland complex that historically absorbed monsoon flooding for a low-lying city of over 2.5 million people. From the mid-2010s the World Bank-supported Metro Colombo Urban Development Project (MCUDP, $313 million: $213m World Bank, $100m Government of Sri Lanka) funded citywide drainage and wetland works, including the roughly $1.2 million restoration of the Beddagana wetland park. In 2018 Colombo became one of the first 18 cities worldwide, and the only capital, accredited under the Ramsar Convention's Wetland City scheme.

A peer-reviewed valuation study puts the flood-control value of the wetland complex at roughly $72 per square metre, with restored wetlands able to absorb up to 40% of floodwater in peak events and directly protect an estimated 232,000 people; without functioning wetlands the city risks losing about 1% of its GDP annually to flood damage. These gains are not secure: independent research documents wetland loss of up to 60% since the 1980s and an ongoing loss rate of about 1.2% (58 acres) a year as urban development continues to encroach, and a 2026 study flags gaps between the city's wetland strategy and its enforcement.