Urban wetlands and disaster resilience of Colombo, Sri Lanka

Purpose: This paper aims to present a long-term research project to understand the nature and extent of degradation in a selected segment of the Colombo Flood Detention Area (CFDA) wetlands. It qualitatively explores the gradual process of change in watersheds and the wetland ecology affecting flood control services, thereby leading to full-blown disasters. It underlines the importance of protecting ecosystem health of urban ecological features for strengthening the disaster resilience of cities. Design/methodology/approach: Through analyzing the long-term change of landscape level parameters, water-quality, vegetation and soil quality, the authors emphasize the potential of an outright ecological regime change and the effects on ecosystem services of the wetlands. Findings: Colombo is a city surrounded by a large and interconnected system of natural wetlands that provides a valuable flood control service. The rapid and partly ad hoc urbanization in the past 15-25 years has caused a steady degradation in the wetlands that severely threatens the ecosystem services. It was found that the native, grass-dominated marshy habitat of the wetland is rapidly transforming into a habitat with shrubs and small trees (44 percent of the extent). Typical peaty soil in the marsh has also changed into a semi-mineral soil. Both changes result in a significant reduction in water-holding capacity of the wetland, thus increasing the flood frequency. Practical implications: These ecological changes have undermined the effectiveness of the repeated cost-intensive engineering measures taken by the authorities to contain floods. Originality/value: CFDA had not been studied previously in an ecosystem services and disaster resilience perspectives. The ecological and hydrological aspects have been studied separately without integration.