Preserving Sri Lanka wetlands helps prevent Colombo flooding: World Bank

ECONOMYNEXT – Preserving wetlands in and around Sri Lanka’s capital Colombo would help prevent its flooding, which in recent years has caused much disruption and damage, a new World Bank report has said.

Nature-based solutions are also used for flood protection, reducing the need for hard infrastructure like dikes, according to the report, an assessment of building infrastructure resilient to climate change and natural disasters.

It advocates combining green and gray infrastructure to provide lower-cost, more resilient, and more sustainable infrastructure solutions, such as putting nature to work to protect infrastructure.

Grey infrastructure includes the pipes, pumps, and detention ponds engineered by people to manage stormwater, for instance, while green infrastructure includes planting trees and restoring wetlands.

Recent floods in Sri Lanka have caused damage and disrupted operations of several listed firms like a brewery and a construction company located near the banks of the Kelani river which runs around the city.

Poor urban planning and weak enforcement of regulations has meant much of the wetlands have been filled up and built upon in recent decades.

The government has begun allocating funds for disaster relief in recent budgets to avoid having to prune spending elsewhere to cope with unforeseen flood damage and disruption.

The World Bank report said that in Colombo, preserving the wetlands system proved to be a cost-effective solution to reduce flooding in the city, even when taking into account land development constraints.

It refers to a study of Colombo’s floods, conducted amid large uncertainties about climate change and urban development, which evaluates various choices for the preservation of wetlands.

The study looks specifically at how much regret decision makers would experience in 2030, comparing the realized level of risk and the best possible outcome.

The study finds that all conservation levels could lead to zero regret. In other words, for each conservation level measured on a scale of between 0 and 100 percent, there is at least one scenario in which the level is optimal.

“But if a small share of the wetlands is preserved and the rest is developed, the potential for regret is high: in scenarios with a major increase in rainfall and river runoff, high population growth, and high building vulnerability, the development of wetlands would lead to substantial flood losses,” the report said.

“And because wetlands are difficult and costly to recreate, these losses would be largely irreversible, resulting in high regret.”

By contrast, the conservation of wetlands cannot lead to high regret because the main cost of this option is the opportunity cost of not developing the wetland areas, which is less uncertain than the cost of floods.

“Because conserving wetlands is a reversible solution, if decision makers want to avoid experiencing regret by 2030, they may prefer to conserve Colombo’s urban wetlands for now, wait for more information on how climate and urbanization will evolve, and reconsider their position in a decade or two.”
(COLOMBO, 21 June, 2019)