Sri Lanka must reassess dams as extreme rainfall intensifies, engineer says

Sri Lanka should reassess the safety and capacity of its dams as climate change increases the frequency and intensity of extreme rainfall, water resources engineer Amila Prasad Basnayaka said during an event at the Institution of Engineers Sri Lanka (IESL).

Basnayaka said many existing dams and drainage structures were designed using historical rainfall estimates that may no longer reflect present or future weather conditions.

He made the remarks during a webinar on future-ready stormwater and flood modelling, where he discussed lessons from mining, landfill and urban development projects.

Sri Lanka should use updated rainfall records and climate-change projections to calculate new design standards for dams and other water infrastructure, he said.

Basnayaka said engineers must consider how much rainfall could fall, how frequently extreme events could occur and whether existing structures could safely manage the resulting water volumes.

He noted that Australia had repeatedly revised its engineering guidance to incorporate climate risks. Rainfall levels previously associated with a one-in-100-year event had already increased, while engineers now also model future conditions under moderate and extreme climate scenarios.

Sri Lanka has an extensive network of rainfall monitoring stations and should use the available data to conduct detailed studies on future rainfall patterns, he said.

Such assessments would help authorities identify vulnerable dams, estimate the consequences of possible failures and decide whether they should strengthen structures or introduce additional risk-reduction measures.

Basnayaka said physical alterations might be difficult at some older dams. Authorities should therefore improve emergency planning, public awareness, warning systems and evacuation procedures for communities living downstream.

He also proposed integrating upstream rainfall measurements, reservoir water levels and automated warning systems. Heavy rainfall detected upstream could trigger alerts before floodwater or emergency dam releases reached populated areas.

Basnayaka said recent extreme-weather events had shown the need to review whether older infrastructure could withstand increasingly severe rainfall and flooding.