There has been an increase of 20-24% in the proportion of the global population exposed to floods since the year 2000 according to a new scientific study. The new data is 10 times higher than previous estimates.
The new study ‘Satellite imaging reveals increased proportion of population exposed to floods’ published in a recent issue of scientific journal Nature said climate change projections for 2030 indicate that the proportion of the population exposed to floods will increase further.
The study made use of satellite images to document the rise, which is far greater than had been predicted by computer models. The analysis shows that migration and a growing number of flood events are behind the rapid increase.
In the 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 255m-290m people were directly affected and between 2000 and 2015 the number of people living in these flooded locations increased by 58m-86m. This represents an increase of 20-24% in the proportion of the world population exposed to floods, some 10 times higher than previous estimates.
One of the challenges with flooding is that most maps of where the waters could penetrate are based on models. These simulate floods based on information such as elevation, rainfall and data from ground sensors.
But they fail to consider population or infrastructure changes and are unable to predict random events such as dam breaches. So when hurricane Harvey hit Texas in 2017, around 80,000 homes were flooded that were not on government risk maps.
The study also found that the increase in the exposed population was not evenly spread throughout the world and countries with increased flood exposure were mainly in Asia and sub-Saharan Africa.
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.
University of Arizona professor and lead author of the study Dr Beth Tellman said, “We were able to capture a lot of floods in Southeast Asia more than other places, because they’re so slow-moving and so the clouds move and we were able to get a really clear image of the flood.
“There’s also a large human population that settled near rivers for really important reasons such as agriculture. This, unfortunately, exposes people to a lot of flooding events,” said Dr Tellman.
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%. M