According to researchers, more than 300 million people who live in low-lying river deltas mostly found in less developed nations are exposed to more flooding from global warming.
Due to the climate change brought about by global warming, tropical storms are made deadlier especially to people in these areas. About ten percent live on floodplains that are exposed to cyclones generating 350 kilometer per hour (200 miles per hour) winds, and rain volumes up to a meter (40 inches) per day.
Researchers published their findings in the journal Nature Communications, Tuesday, September 29.
BATON ROUGE, LA - AUGUST 23: A map with locations showing land building projects, levees, floodgates, marsh creation, and barrier island restoration, shoreline protection, river diversions and coastal habitat improvements is displayed at the LSU Center For River Studies on August 23, 2019 in Baton Rouge, Louisiana. The facility includes a 10,000 square feet river model that opened in 2018.
Changes in the Atmosphere Leading to Stronger Storms
Researchers explained that as the oceans become warmer, more moisture goes to the atmosphere which in turn creates stronger storms more frequently. Former cyclones that are described as once-in-a-century are becoming more common. This applies even to locations where strong cyclones are considered even more rare.
Deltas, or areas where rivers meet, are more vulnerable to these weather anomalies - experiencing floods from warm-weather occurrences. Prior to this study, the population of the world thriving in these river deltas was not yet identified as risk factors, adding to the difficulty of planning for the necessary contingencies.
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Researchers noted that people have been living in these locations for millennia, but anthropogenic activities like upstream watersheds had negative effects on these landforms. Since deltas, by nature, exist in low-lying areas like those near sea level, it makes them more prone to flooding.
"The big question we are trying to answer is how many people live on river deltas and what is their vulnerability to coast flooding," said Douglas Edmonds, lead author of the study and a geomorphologist at Indiana University, in a statement to AFP.
A Large Population At Risk of Storm Surges
Researchers then started to study 2017 data covering 2,174 deltas around the world as defined in a previous work. They estimated that at least 339 million people lived in these areas, with only 10 million not coming from developing or least developed countries.
More than 75 percent of these people are living in only 10 river basins, led by the Ganges-Brahmaputra in India with 105 million people and the Nile delta in Egypt with 45 million inhabitants. It revealed that while deltas are only responsible for 0.5 percent of the landmasses on Earth, they provide shelter to almost twenty percent of the world's entire human population.
"We were surprised to learn that most of the deltas with a large number of people living in the 100-year tropical cyclone floodplain are sediment-starved," Edmond explained. He added that this discovery is bad news in the face of rising sea levels, and even stronger storm surges, due to global warming.
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The lead author explained that these landforms exist, usually at the coastline, because of the deposition of sediments near shorelines. As the sea level rises, the delta can either: (1) shrink as it slowly loses ground to the water or (2) fill the threatened area with sediment from the waters.
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