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Floods: number of people exposed is 10 times higher than previously believed

2021-08-04T23:34:48.147Z


Floods are getting worse and the number of people exposed is 10 times what was previously believed, according to a new study.


Belgium opens investigation after deadly floods 0:24

(CNN) -

In the midst of a deadly summer from flooding in different parts of the world, a group of scientists found that the number of people at risk of extreme flooding has increased significantly in the past two decades.

In Germany, severe floods claimed the lives of at least 173 people.

In Nigeria, the island of Lagos suffered one of its worst floods in recent years, submerging houses and cars.

And earlier this week, Chinese officials announced that the death toll from the July floods rose to 302, more than triple the previous estimate.

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Climate change makes extreme floods worse and, in this context, a study published on Wednesday in the journal

Nature

concludes that the population exposed to these floods since 2000 is 10 times greater than previously estimated by migration people to flood-prone areas.

"It is not surprising that we are seeing really big and potentially unprecedented floods affecting countries like China," Beth Tellman, lead author and co-founder of Cloud to Street, told CNN.

This is an analytics firm that developed the Global Flood Database, which is used as the backbone of the new research.

"This is exactly what climate models have predicted," he explained.

See the devastation left by the floods in China 1:21

The study comes just days after the UN Intergovernmental Panel on Climate Change (IPCC) releases a key state-of-the-art report, which is expected to describe how extreme weather events as floods, cyclones and rising sea levels will worsen and become more frequent due to human-caused climate change.

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About 90% of the floods occurred in South and Southeast Asia

Scientists from Cloud to Street, NASA, Google Earth, and universities analyzed global flood exposure using satellite observations and created the largest flood dataset ever produced.

The data maps the maximum extent of water during 913 major floods between 2000 and 2018.

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Guy Schumann, a research scientist who was not involved in the study, who specializes in flood data and models, told CNN that it is great to have a database with which to test the models and "especially on a global scale," because traditionally they were available "at the local level or, at best, at the national level."

Using the database, the scientists identified where large floods occurred in the past two decades.

And they found that about 90% of the floods occurred in South and Southeast Asia, particularly China and India, countries where migration has increased significantly since 2000.

They were trapped in a subway flooded 1:12

Tellman, who has worked on this research for the past five years, said it was "shocking" to see the increase in flooding in places where the population also grew significantly.

And now floodplains are found more frequently in urban areas, he said.

"That was when we realized that floodplain development was a very serious problem," Tellman said.

The researchers found that between 2000 and 2015, roughly 58 to 86 million people moved to flood-prone regions.

This translates into an increase of about 20% in the population exposed to floods.

More countries will face increasing floods

Flooding and the number of people exposed will continue to worsen, according to the study.

Thirty-two countries are already experiencing increasing floods, and 25 more countries will be added to that list by 2030 unless greenhouse gas emissions are significantly reduced, the researchers found.

Floods devastate communities in Germany 1:38

Low-income communities are often the most exposed to risk, as they tend to have no choice but to settle in less favorable and less expensive areas that are more prone to flooding.

"It's not that people necessarily want or choose to live in a high-risk location, but they may have no other option or no public housing program in their country," Tellman said.

In 2007, for example, floods from a deadly cyclone killed approximately 1,000 people and displaced 9 million in Dhaka, the capital of Bangladesh.

The analysis shows that, during the study period, Dhaka also experienced an increase in population in poor flood-prone areas.

The Cloud to Street study mapped floods and their duration around the world.

The rains caused 86 days of flooding in South Asia in 2007, displacing millions of people in India, Nepal, Bhutan, Pakistan and Bangladesh, according to the Cloud to Street Global Flood Database.

The infrastructure factor

In addition to flooding caused by heavy rains, tropical storms, and snowmelt, the database also takes into account floods caused by dam failures.

Although they accounted for less than 2% of flood events, dam failures had the largest increase between 2000 and 2015, at 177%, exposing vulnerable populations.

Tellman said it is likely due to what hydrologists call the "dike effect."

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"When we have infrastructure like a dam or a levee, people feel safe and they feel that the land is protected, so its value increases and we build things there," he said.

"The problem is that if the dam is not maintained, it can become a huge danger and affect many people," he explained.

In 2008, the levees along the Koshi River collapsed and destroyed the homes of more than three million people in India and Nepal.

In 2018, heavy rains and the subsequent release of water from the Bagré dam in Burkina Faso flooded thousands of hectares of agricultural land in neighboring Ghana, exacerbating food insecurity in the region.

This country would be better prepared for a global collapse 0:43

Researchers say these incidents demonstrate the deadly cost of poor infrastructure, exacerbated by climate change.

Philip Ward, professor of global water risk dynamics at the Free University of Amsterdam, told CNN that the study's findings emphasize the importance of maintaining infrastructure and strengthening resilience.

He also said the results suggest that officials should devote more resources to the warnings.

"We have to make sure that there are still early warning systems, evacuation plans and good communication between the most vulnerable, political officials, emergency services, etc.," said Ward, who was not involved in the study.

A valuable database

Satellite observations capture realities that are not typically captured in predictive climate models, according to Tellman.

Most flood-prone area maps, including those used by government agencies like the Federal Emergency Management Agency, rely on models that simulate flooding based on historical data.

Their results may be limited as climate change drives flooding to record levels.

A Nigerian city could disappear in this century 0:36

Outside experts said Cloud to Street's population analysis will strengthen the data they already have, especially as the weather changes.

"The most important thing about this research is the database itself," Ward said.

"As someone who models flood risks, this data will really allow us to better validate the models and compare them to reality," he explained.

Tellman hopes that, as climate change fuels more extreme and far-reaching flooding, the new analysis will encourage policy makers to invest in equitable climate adaptation measures in places where exposure to flooding has grown faster than normal. surrounding population.

"Who is affected by the floods is really under our control," Tellman said.

Floods

Source: cnnespanol

All news articles on 2021-08-04

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