Across Southeast Asia, huge areas of land are now closer to sea level than previously realised. Information from a new study using advanced satellite imagery, highlights millions of people will face the risks of flooding.
Low-lying countries like Thailand, Indonesia, Vietnam and the Philippines are vulnerable to sea level rise. These countries have land prone to sinking due to subsidence. This means that people in these countries will face extreme sea level events that will progressively get worse every year. The cause of this worsening weather is due to climate change.
Previous data was inaccurate
A lack of accuracy in satellite radar data that measures land elevation levels has inaccurately reduced past coastal flood risk assessments and projections.
However, Dutch based research institute Deltares has recently performed the first global elevation model with a more accurate picture. Deltares obtained the more accurate picture from new satellite Light Detection and Ranging (LiDAR) data.
Dr Aljosja Hooijer is the co-author of the report prepared by Deltares. Hooijer explains that the “Most existing elevation models for the region, and indeed globally, were based on radar data which cannot fully penetrate vegetation and therefore yield a land elevation that is often too high by one or several metres.” The report made in late June, was published in the Nature Communications journal.
Dr Hooijer told news media house CNA, “If the assumed land elevation is too high, the resulting calculated flood risk is too low.”
In Indonesia, the land area below 2m detected by LiDAR is more than 14 times than previous data. Previous information came from the Shuttle Radar Topography Mission (SRTM) data which is more commonly used.
The amount of land below 2m in Thailand detected by LiDAR is about five times SRTM estimates. In the Philippines, it’s seven times more than SRTM estimates.
The figures can vary
The researchers stressed that at a local level, these figures can vary. Planning officials can only reduce flooding risks with more precise data in hand.
The burden of current coastal flood risk and future rise in sea levels is disproportionate in tropical regions, especially Asia. This is according to the researchers at Deltares.
The Deltares study estimates areas below 2m above sea level is home to nearly 157 million people in tropical Asia. It predicts severe impacts in these low-lying areas. If sea levels rise in the coming decades, as they have been forecasted, this number would increase significantly.
Projection of extreme global flooding
The Intergovernmental Panel for Climate Change projects a rise of 0.8m in sea level, possibly by 2100. By the end of the century, extreme flooding events which happen once a century could occur every year.
Densely populated areas of major deltas will be under water, should there be a sea level rise of 1m. It is possible where the rise in sea level will pose a high risk of permanent flooding for some 129 million globally.
Dr Hooijer said “We knew the numbers would be high, as we see flooded and nearly flooded land along many coastlines. But to find two-thirds of the lands and people most at risk in developing tropical countries was more than we expected.”
Large numbers for Asia
Hooijer continued, saying, “The numbers for Asia are especially large. It could be said that half the global coastal flooding problem is in tropical Asia alone – a bit more by population, less by area.”
According to a forecast in the study, by 2100, a scenario with a 1m rise in sea level would affect 3 main countries. These countries are Vietnam (nearly 38 million people), Thailand (23 million), and Indonesia (28 million). People in these 3 countries would be living in zones at high risk of frequent coastal flooding if the 1m sea level rise occurs. This is a 21 percent increase in comparison to current day figures.
The estimate figures do not take into account any growth of population or movement of people towards coastal areas. According to Dr Hooijer, this makes those estimates conservative. He said “Many scientists believe coastal populations will keep increasing.”
7th July 2021 23:00
This article brought to you by Legacy Times 传城时代