Floods are endangering millions of people more than previously estimated

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Floods pose a serious risk to tens of millions of people more than scientists previously estimated. As many as 86 million people lived in flooded areas around the world in 2015 compared to 2000, according to the new research published today in the journal Nature.

Thanks to satellite remote sensing, scientists were able to build the most comprehensive set of observed flood data, they said. It shows that more and more people have moved to the beach where they are in danger. The results also suggest that older flood maps used in urban planning and insurance may underestimate the real flood risk.

Last month, shockingly severe floods have claimed hundreds of lives China, Germany and Belgium. Just a few days after the year, rainfall sank in Zhengzhou, a city in Henan Province. Record rainfall all over Western Europe drowned dams and almost washed away entire cities.

“It just really hits home, the urgency of the problem,” says Colin Doyle, one of the authors of the new study and director of Cloud to Street Technology, a flood monitoring and risk analysis platform. “It is now urgent to address the issue of flexibility – both to adapt to events and to create the infrastructure as a safety net.”

The proportion of people living in flood-prone areas has increased by 20-24 percent since 2000, according to a new study. That’s up to ten times more than previous studies had estimated. The increase was due to a few different factors.

First, satellites have given scientists a better picture of the floods. In the past, most flood maps were based on models and not on observations of actual floods. Scientists like Doyle now have more satellites in space and more cloud services, and have new tools.

During their extensive global research, Doyle and his writers were able to view images taken daily by two NASA satellites to study the floods that occurred between 2000 and 2018. their observations. (The Interactive Global Flood Database was released today with a new study website, check out the new maps compiled by Doyle and colleagues.)

Thanks to satellite data, Doyle and his writers can view more different types of floods than typical flood maps. These included floods from dam damage, snowmelt, and surface water floods. On the other hand, modeling limits traditional flood maps to the hazards that arise when heavy rains cause rivers and other water bodies to swell.

But the rise in flood risk documented by Doyle and his colleagues is not just a reflection of technological advances. The new development seems to be focused on places more prone to flooding. Population growth in these high-risk areas outpaced global population growth over the same period. It is due in part to poverty and the lack of other alternatives for many vulnerable populations, the study notes.

While more accurate flood maps can give urban planners a better idea of ​​where protection infrastructure needs to be increased, they can also tell them where No to build in the future.

“For some communities, the only option is to manage their withdrawal from the floodplains,” writes Brenden Jongman, a World Bank disaster risk management specialist who researched the study and wrote the attached opinion article. Nature.

Doyle and Jongman point out that flood maps in large cities can still be improved. Satellites had a harder time peeking into densely packed areas. “If you’re above New York and you look down, you mostly see the peaks of all the skyscrapers,” Doyle says.

Newer commercial satellites can take images at higher resolutions, but it is still expensive for scientists to use this data. And while newer satellites could take a better picture, they may not have been long enough for scientists to look as far as Doyle and his colleagues could with NASA satellites.

Hopefully time will open up these tools to researchers as well. They need all possible help to predict future flood risks. Climate change is raising sea levels and eating the coasts and estuaries that millions of people call home. Rising global average temperatures may as well boil storms and lead more heavy rain In some areas. Nature Research predicts that by 2030, more and more people will be exposed to dangerous floods.

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