New US report details effects of rising sea levels

A new US report concludes that Florida and Louisiana are the states most vulnerable to sea-level rise, followed by North Carolina and Texas.

The new report focuses on the coastal states from North Carolina to New York where the rates of sea-level rise are moderately high. The region has extensive coastal development, a high population and is likely to be at increased risk.

“You’re vulnerable,” said Jim Titus, project manager for sea-level rise for the US Environmental Protection Agency and lead author of the report, Coastal Sensitivity to Sea Level Rise: A Focus on the Mid-Atlantic Region. “The people whose land could be permanently submerged aren’t even flooded today.”
A rise in sea level increases the vulnerability of development in coastal floodplains and diminishes the rate at which low-lying areas drain. It will result in a loss of wetlands in the mid-Atlantic region.
Rising temperatures cause ocean waters to warm and expand, like water heated in a tea kettle. In addition, rising temperatures near the poles cause massive ice sheets to melt, adding to the volume of water.
The report predicts that coastal erosion will occur at higher rates as sea level rises. Particularly in the sandy shore of the mid-Atlantic coast, the report says, it is nearly certain that barrier islands, spits and coastal headlands will erode faster due to sea-level rise. The Outer Banks are particularly vulnerable.
The report, produced by a collaboration among agencies including the US Geological Survey, the National Oceanic and Atmospheric Administration and the Department of Transportation, offers three scenarios for sea-level rise by 2100: A rise of about 16 inches (40.6 centimetres), of about 2 feet, and of about 3 feet.
In 2007, an international scientific panel projected that sea level would likely rise between 7 inches and 2 feet by 2100. Those estimates do not take into account any contribution from rapid changes in ice flow from Antarctica or Greenland.
Rising sea levels might be especially disastrous to North Carolina, as some sections of the coast are slowly sinking, magnifying the effects of rising seas.
Tide-gauge readings in the mid-Atlantic indicate that relative sea level rise (the combination of rising waters and sinking land) was generally higher – by about a foot – than the global average during the 20th century.
If sea level should rise more than three feet during the 21st century, the report says, “it is likely that some barrier islands in this region will cross a threshold” destabilising and breaking apart.
As sea level rises, the most basic decision that states and beach communities must wrestle with is whether to try to hold back the sea or let nature take its course. Both have costs.
Replenishing sand on eroding beaches allows houses and businesses to remain in place for a period of time, but is expensive to maintain. Retreating from the rising sea avoids the costs but concedes a loss of land and, in a worse case, entire communities, the report notes.
Greg Rudolph, shore protection officer for Carteret county, North Carolina, said people generally accept that sea level is rising. But planning for something that is occurring over decades is difficult.
“Let’s face it, we live on four-year cycles when people are elected,” Rudolph said. “Not many people are going to plan out 14 years or 21 years in advance.”

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