Vietnam Experts Dispute Degree of Flooding in Country’s South by 2050

vietnam-underwater2-110419.gif Map on right shows areas in southern Vietnam predicted to flood.

Recent predictions of an increased vulnerability to coastal flooding in southern Vietnam due to rising sea levels are overstated, with populations in the country’s Mekong Delta unlikely to be forced to relocate by 2050, some scholars say.

New methods of calculating land elevations above sea level show that by that date “the bottom part of the country will be underwater at high tide” a New York Times article on Oct. 29 says, quoting a report by New Jersey-based Climate Central.

“More than 20 million people in Vietnam, almost one-quarter of the population, live on land that will be inundated,” the Times article says, adding, “Southern Vietnam could all but disappear.”

“[And] much of Ho Chi Minh City, the nation’s economic center, would disappear with it, according to the research,” the Times goes on to say.

Speaking in an interview with RFA’s Vietnamese Service, independent Mekong researcher Nguyen Huu Thien said however that the original report by Climate Central contains none of the sensational language used in the Times report.

Climate Central’s findings are based on a new approach called CoastalDEM, used to correct for possible errors in a satellite-based approach that calculates land elevations based partly on the height of buildings and the height of trees, and where dense fauna conceal the actual level of the land, Thien said.

“And this [new] approach serves mainly to warn the world that millions of people may end up living in regions lower than sea level if the world doesn’t reduce its carbon emissions,” he said.

'A greater concern'

Research by scientists from the Netherlands shows that with an average rise in sea level of 40 centimeters (15 ¾ inches), the Mekong Delta will be under sea-level only in another 80 years, Thien said, adding that a greater concern is the rate at which the land itself is sinking.

“Of the two causes that threaten the Mekong Delta—the rise of sea water and the sinking of the land—the former cannot be controlled, and the latter is more worrisome and should be addressed as a top priority to be solved,” he said.

“The reason is that sea water is rising at about 3 millimeters (0 1/8 inch) per year, while the Mekong Delta is sinking at a rate of about three or four times, and in some places ten times, higher than that.”

To prevent further sinking, farmers’ use of underground water should be urgently reduced, with intensive farming methods focused on quantity changed to less intensive methods focused on the quality and value of the food produced, he said.

More research needed

Also speaking to RFA, Le Anh Tuan, a research scholar at the Climate Change Research Institute of Vietnam’s Can Tho University, agreed that the exploitation of underground water sources in the Delta region is a major cause for concern.

“When more underground water is taken, the Delta loses its underground support, which leads to gradual sinking,” he said.

“In addition, the dredging of sand is also a cause for the sinking and sliding of land, and the holding back of sediment by upstream hydropower dams also raises the risks of sinking.”

In any case, the predicted date for inundation by 2050 cannot be verified, Tuan said.

“We know the degree of elevation already, but how much surface will be underwater, and in what year, needs concrete research, and the information from CoastalDEM should be handled cautiously,” he said.

Meanwhile, tides rise and fall, and land flooded during periods of inundation will emerge again when the tides recede, he said.

“Not everyone living in those areas will have to leave,” he said.

Reported by RFA’s Vietnamese Service. Translated by An Nguyen. Written in English by Richard Finney.

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