Rising sea levels pose unique tsunami risk to Macau

Rising sea levels around the world will pose a greater risk of tsunamis striking Macau, a new academic paper has found, especially in the low-lying parts of the city, which are already prone to flooding.

The authors of the paper, which was published in Science Advances, came to their conclusions based on computer simulations accounting for sea level rise foreseeable over the next century. They found that higher sea levels are likely to increase both the frequency and the intensity of tsunamis and tsunami-induced flooding.

The authors found that even a conservative sea level rise of just 0.5 meters by 2060 and 1 meter by 2100 would dramatically increase tsunami-induced flooding incidences by a factor of 1.2 to 2.4 and 1.5 to 4.7 respectively.

According to the scientists, Macau would become particularly prone to such natural disasters because of its location in the South China Sea and its proximity to earthquakes generated along the Manila Trench.

Megathrust earthquakes generated along the Manila Trench remain the major source of tsunami threats in the South China Sea. According to the authors of the paper, there is ample evidence to suggest that the megathrust is capable of producing basin-wide tsunamis. They argue that higher sea levels would allow even small tsunami waves to extend further inland.

The areas most at risk include Macau’s low-lying but densely-populated urban districts, such as the Inner Harbor area and reclaimed land plots.

However, the southern coastal areas of Coloane may also be at risk, given that they are closest to the origin point of a potential tsunami and may bear most of the initial impact, notwithstanding the fact that the once-island is home to the highest peaks in Macau.

In contrast, much of the rest of Taipa and Coloane is less at risk than the Macau peninsula – including the Cotai Strip and other central areas – because they are protected by favorable topography features of the SAR.

The researchers ran a worst-case scenario in the simulation using current sea levels. The model showed that almost all reclaimed land in Macau would be flooded, leaving only the “original islands untouched.”
Flooding of up to 5 meters would be experienced in the Inner Harbor area, the northeast Macau Peninsula and the southern tip of Coloane. Even the more protected areas of the Cotai Strip and the University of Macau might face water of up to 3 meters deep.

Macau is one of the most densely-populated places on the planet, with around 21,400 people per square kilometer as of last year. More than 60 percent of Macau’s land area is reclaimed land at or slightly above sea level, while the Inner Harbor area is in some places 2 meters below the average sea level today. DB