The lessons learnt since 2004

On Boxing Day 2004, an earthquake in the Indian Ocean near Indonesia set off a tsunami which killed almost 250,000 people. It was the deadliest natural disaster this century, and was probably the deadliest tsunami in human history.

- RAVINDRA JAYARATNE AND TOMOYA SHIBAYAMA

As coastal engineers who specialise in tsunamis and how to prepare for them, we have seen how the events of 2004 reshaped our global disaster management systems. Among the lessons learned since that day, three themes stand out.

First, the importance of early warning systems, providing time to escape impact zones. Second, the importance of local preparations and educating people about the risks. Finally, the ongoing need for—but not overreliance on—coastal defences.

The absence of a comprehensive early warning system contributed to the devastating loss of life in 2004. About 35,000 people died in Sri Lanka, for instance, which wasn't hit until two hours after the earthquake.

Significant investment has been made in the years since, including the Indian Ocean tsunami warning system which operates across 27 member states. This system was able to issue warnings within eight minutes when another earthquake struck the same part of Indonesia in 2012. Similarly, when an earthquake hit Noto, Japan, in January 2024, swiftly issued tsunami warnings and evacuation orders undoubtedly saved lives.

However, these systems are not in use globally and weren't able to detect the tsunamis that swept the Tongan islands in 2022 following the eruption of an undersea volcano in the South Pacific. In this instance, better monitoring of the volcano would have helped detect the early signs of a tsunami.

But early warning systems alone are not enough. We still need education and awareness campaigns, evacuation drills, and disaster response plans.