More people live in areas affected by floods

And the global population grew by 18.6% between 2000 and 2015, the population in these areas was higher than that, while at the same time increasing by 34.1%. This means that 58 million and 86 million more people were affected by the floods in those places in the last 15 years.

“It’s not particularly surprising that floods are increasing,” he says Beth Tellman, the initial co-founder of flood maps On the cloud and lead author of the study. “But it struck me that people go to places we’ve seen floods in the past.”

The researchers studied more than 3,000 events Dartmouth Flood Observatory a database that records reported flooding in media coverage. The events containing the location data were linked to satellite imagery FASHION, An instrument mounted on two NASA satellites that have captured daily images of the Earth since 2000.

The researchers used an algorithm to map where the flooding covered the pixels covered with water and which did not. They then added population data to see how trends in flooded areas have changed over time.

Low- and middle-income countries have experienced the fastest population growth in flood-affected areas in the last two decades, with sub-Saharan Africa and sub-Asia having the highest growth rates.

Socioeconomic factors can explain a movement, Tellman says. Weak groups have no choice but to settle in floodplains because the land can be cheaper and more accessible.

Using satellite imagery, the researchers described the effects of actual flooding more accurately than traditional models. Patterns can take on some types of flooding, such as those that occur around rivers and along coasts. As for others caused by heavy rainfall or random events (such as a storm surge that breaks the dam or aligns with the high tide), satellite imagery provides a clearer picture.

The 913 mapped floods are just a few thousand of the thousands that occur worldwide each year. “It’s just the tip of the iceberg,” Tellman says.

MODIS takes images with a resolution of 250 meters, about the length of two football fields. This means that researchers cannot map smaller floods or map them in most cities. Clouds also hampered the image processing algorithm and as satellites passed through a specific place on Earth only once or twice a day, they also lost short-term floods.

The new tools have much higher resolution and can be seen through the clouds, he says Bessie Black, Founder and CEO of Cloud to Street. These tools, along with artificial intelligence, can now map floods even more accurately. But in order to systematically map floods over time, researchers had to paste them with images from a source, using technology that has been around for a long time.

The effort provides scientists with a clearer picture than the scale of recent floods and any other means of human impact. And the results will be especially useful for modelers who are trying to predict risk, he says Philip Ward, who studied flood risk assessment at the Vrije Universiteit Amsterdam and was not involved in the research.