Floods to Come More

 A new study shows that the percentage of the global population at risk from flooding has risen by almost a quarter since the year 2000.

By 2030, millions more will experience increased flooding due to climate and demographic change, the authors of the analysis said.

Satellite images the rise is far greater than had been predicted by computer models.

Flooding is an environmental disaster that impacts more people than any other, say researchers. That view has echoed around the world in recent weeks such as in Germany and China, where huge floods took lives and destroyed property.

In this new study, researchers looked at daily satellite imagery to estimate both the extent of flooding and the number of people exposed to over 900 large flood events between 2000 and 2018. They found that between 255 and 290 million people were directly affected - and between 2000 and 2015, the number of people living in these flooded locations increased by 58-86 million.

This represents an increase of 20-24% in the proportion of the world population exposed to floods, some 10 times higher than previous estimates. Around 90% of the flood events observed by the scientists were in South and Southeast Asia, around the basins of major rivers including the Indus, Ganges-Brahmaputra and the Mekong.

The key drivers of flooding are heavy rainfall, tropical storms or surges and snow and ice melt. Dam breaks represented less than 2% of floods but had the highest increased incidence in terms of the population exposed.

One of the puzzling aspects of the research is why people in many countries are moving into flood-prone areas rather than away from them. While the global population grew by over 18% between 2000 and 2015, in areas of observed flooding, the population increased by 34%.

Economics plays an important role.

"Places that have flooded tend to be really cheap land for informal development, so in Guwahati, India, and Dhaka in Bangladesh, we see people moving in, and so flooded areas then become settled," Dr Beth Tellman from the University of Arizona, explained. "It may not be people's choice to live in those areas because they might not have a lot of agency. If there were really good public housing programmes or other options, I think people probably wouldn't choose to settle in a hazardous area."

Looking to the future, the authors say they expect the numbers at risk of flooding to continue to rise. They estimate that by 2030, there will be an extra 25 countries experiencing increasing floods in addition to the 32 being impacted at present.

"We estimate that an additional new 179.2 million people will be exposed to floods by 2030 in 100-year zones and most of that is due to demographic change," said Dr Tellman. "Around 50 million people extra people will be exposed to inundation, we think, due directly to climate change explicitly."

Floods: Research shows millions more at risk of flooding - BBC News