Global population exposed to floods grew over 20% in 15 years: Study

The growth was concentrated in Asia and sub-Saharan Africa

By DTE Staff
Published: Tuesday 28 September 2021
Global population exposed to floods grew over 20% in 15 years: Study
Photo: Abdul Kalam Azad

The number of people living in floodplains across the world increased by 58-86 million during 2000-2015, according to a new estimate. This indicates a 20-24 per cent growth in the period, the report noted. 

The growth spread over 70 countries was concentrated in low- and middle-income countries, mostly in Asia and sub-Saharan Africa, the report published in the journal Nature stated. “At least 213 million people were shown to be exposed to flooding in south and southeast Asia alone.”

The latest estimates are 10 times higher than previous models, the analysis showed. 

“More than 255 million people were affected at least once by major floods in that period,” the report said. 

Exposure to flooding (2000-2015)


Source: Nature


Migration and urbanisation are major factors behind this growth. Most of those moving to flood-prone areas may be “the most vulnerable, marginalised populations” who had nowhere else to go, wrote the group of scientists who conducted the study. 

Reclassification of land following major floods and rising sea levels is another cause for the increase in population in these regions, according to the authors. 

Researchers from the National Aeronautics and Space Administration (NASA) of the United States, the University of Colorado, the University of Arizona, Columbia University, the University of Washington, the University of Texas and the University of Michigan analysed satellite data of 913 large flood events across 169 countries over 20 years. 

Flood models based on satellite observations go beyond the risk perspective and estimating the impacts of flood risk on populations, said Jonathan Sullivan, a postdoctoral scientist at the University of Arizona and one of the authors. He added: 

Satellite imagery can help us understand things like the impact on households, income, wealth, and human health after a flood.

These data sets take into account dam breaks and snowmelt that were not part of past models, he added. 

The findings have been made available at Global Flood Database by Cloud to Street, a collaborative project dedicated to flood risk assessment and science-based action. 

‘Blue lining’ or the unofficial demarcation of flood-prone areas by financial institutions has led to “underinvestment in flood mitigation infrastructure” and increased risks, the report added. 

The term draws from ‘red lining’ which is a malpractice leading to racist housing policies towards specific communities in neighbourhoods. 

To circumvent these hurdles, the researchers called on city planners and government agencies to use the database and NASA’s new sea level projection tool to determine the best action to protect against future flooding.

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