Long-term Strategic Planning for a Resilient Metro Colombo: An Economic Case for Wetland Conservation and Management

Abstract:

Colombo faces recurrent floods that threaten its long-term economic development. Its urban wetlands have been identified by local agencies as a critical component of its flood reduction system, but they have declined rapidly in recent years due to continuous infilling, unmanaged land development and dredging to create lakes. In collaboration with government agencies, NGOs and local universities, the World Bank has carried out a Robust Decision Making analysis to examine the value of Colombo urban wetlands, both in the short-term and long-term, and identify what are the most viable strategies available to increase the city's flood resilience in an unclear future (in terms of climate change and patterns of urban development). This has involved the use of numerous hydrological and socio-economic scenarios as well as the evaluation of some wetlands benefits, like ecosystem services, wastewater treatment, or recreational services. The analysis has determined that if all urban wetlands across the Colombo catchment were lost, in some scenarios the metropolitan area would have to cope with an annual average flood loss of approximately 1% of Colombo GDP in the near future. For long-term strategies, trade-offs between urban development, lake creation and wetland conservation were analyzed and it was concluded that an active management of urban wetlands was the lowest regret option. Finally, the analysis also revealed that in the future, with climate change and fast urban development, wetlands will not be sufficient to protect Colombo against severe floods. Pro-active urban planning and land-use management are therefore necessary, both to protect existing wetlands and to reduce future exposure. The use of many different scenarios, the consideration of several policy options, and the open participatory process ensured policy-makers’ buy-in and lead to the decision to actively protect urban wetlands in Colombo.