A man pushes his tricycle through floodwaters following rain in Kolkata, India on Friday. Several parts of the city reported waterlog on Friday following a heavy overnight downpour. Photo: AFP

The number of people exposed to floods worldwide has surged almost a quarter over the last two decades, according to satellite-based data unveiled on Wednesday that shows an additional 86 million now live within flood-prone regions. 

Flooding is by far the most common of extreme weather events made more frequent and potent by rainfall patterns supercharged by climate change. 

Deadly inundations, such as recently in India, China, Germany and Belgium, inflict billions worth of damage, often disproportionally affecting poorer sectors of society.

Most flood maps rely on modeling based on ground-level observations such as rainfall and elevation, but they can often entirely miss regions that are historically not flood-prone. 

To fill in those gaps, a team of US-based researchers examined satellite data from twice-daily imaging of more than 900 individual flood events in 169 countries since 2000. 

They used the data to create the Global Flood Database, which provides open source information on the death toll, displacement and rainfall levels linked to each of the 913 floods.  

Writing in the journal Nature, the researchers found that up to 86 million people, driven by economic necessity, moved into known flood regions between 2000-15 - a 24 percent increase. 

A total of 2.23 million square kilometers were flooded between 2000-18, affecting up to 290 million people. And it's only going to get worse. 

Computer modeling produced estimates that climate change and shifting demographics would mean an additional 25 countries facing a high risk of flooding by 2030. 

Lead study author Beth Tellman, a researcher at Columbia University's Earth Institute, said the number of additional people now at risk of flooding was 10 times higher than previous estimates. 

AFP