Partly funded by the World Bank, officials plan to expand canals, water retention tanks and related infrastructure development by 2017.
"The Metro Colombo Urban Development Project is a very critical high priority project as it addresses flood reduction in the city," the World Bank's country director Diarietou Gaye said during the project's launch Monday.
The project will dredge primary and secondary canals and lakes, upgrade drains systems within the municipal council and build capacity in agencies about drainage management.
Colombo's low laying areas including main roads get inundated following 30 minutes of strong rain, due to overflowing storm water drains, slowing down economic activity and causing major traffic blockades in the city.
Unauthorised constructions on drainages and lack of regular maintenance and cleaning are blamed for recurrent floods to the city of some 600,000 residents.
The Urban Development Ministry says uncontrolled landfill and flood plain encroachmen