Study finds U.S. threatened by more frequent flooding

Research finds cities on the East Coast of the United States that were founded near the end of the 16th century are at least 45 centimeters lower today than back then due to glacier effects.
By Amy Wallace   |   Sept. 11, 2017 at 11:44 AM
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Sept. 11 (UPI) -- Researchers have found that the East Coast of the United States will be threatened by even more frequent flooding in the future.

The timing of the study's release comes as the Gulf Coast of Texas and both coasts of Florida experience severe flooding from Hurricanes Harvey and Irma.

The study by researchers from the Universities of Bonn, South Florida and Rhode Island, showed the states of Virginia, North Carolina and South Carolina are the most vulnerable with their coastal regions being eroded by water by up to 3 millimeters per year.

Researchers found flooding occurs not just from hurricanes but also can occur on relatively calm days or during normal rain fall causing damage to houses and roads.

"There are primarily two reasons for this phenomenon," Makan A. Karegar from the University of South Florida, currently a guest researcher at the Institute of Geodesy and Geoinformation at the University of Bonn, said in a press release.

"During the last ice age around 20,000 years ago, large parts of Canada were covered by an ice sheet. This tremendous mass pressed down on the continent." Some areas of the earth's mantle were thus pressed sideways under the ice, causing the coastal regions that were free of ice to be raised. "When the ice sheet then melted, this process was reversed," explains Karegar. "The East Coast has thus been sinking back down for the last few thousand years."

The phenomenon known as nuisance flooding will occur more frequently after researchers evaluated data from the East Coast of the United States including GPS and satellite data showing large parts of the coast are slowly and steadily sinking into the Atlantic Ocean.

Researchers found that the area between 32 and 38 degrees latitude has been sinking more rapidly than in the previous millennia, by more than 3 millimeters a year in some cases believed to be cause from the significant use of groundwater in the region.

"When groundwater is removed, the land mass can be compressed more greatly," Karegar said. "It practically collapses into itself and thus sinks even more."

Research finds cities on the East Coast of the United States that were founded near the end of the 16th century are at least 45 centimeters lower today than back then due to glacier effects. More sinking has occurred in recent years from the removal of groundwater and also rising sea levels due to global warming are all believed to contribute to the increase in flooding.

"Even if the removal of groundwater is reduced, the number of floods will thus continue to increase," Karegar said. "The sums of money that need to be spent to rectify the damage associated with this will also increase significantly. One should, therefore, assume that the USA has a vested interest in combating climate change with all its resources."

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