Hurricane Matthew’s march past the Southeast coast in October wiped out protective dunes in four states, newly released aerial photos from the U.S. Geological Survey show.
Matthew overwashed 177 miles of dunes, including 58 percent of those in South Carolina, say USGS experts who analyzed before-and-after photos. Even so, the impact was less extensive than expected.
Agency scientists are still assessing how the damage will affect the region’s most vulnerable shorelines. Dunes are the first line of defense against storms and beach erosion, protecting houses and roads behind them.
“High altitude images give us a big picture view of the coastline, and that’s very useful to identify large areas of overwash, but we can’t see the dunes in those images,” research oceanographer Joseph Long said in a USGS article. “These low-altitude photos give us a clear view of the dune itself. We can see whether the storm surge altered or eliminated that protective barrier, and what happened to the houses and boardwalks and sea walls behind it.”
Matthew reached Category 5 in the Atlantic, causing widespread destruction, before making landfall at McClellanville, S.C., as a Category 1 storm. It pelted North Carolina with heavy rainfall, flooding coastal rivers and towns for days. The storm left 25 people dead and $1.5 billion in damage.
Its storm surge on the Southeast coast peaked at nearly 10 feet above predicted tides, the USGS said.
The storm surge and waves overwashed 9 percent – or 30 miles – of North Carolina’s dunes, 30 percent of Georgia’s dunes and 11 percent of the dunes along Florida’s Atlantic coast.
The U.S. Army Corps of Engineers, working with the USGS, is conducting a month-long series of flights to estimate the volume of sand that Matthew moved off southeastern beaches, measure the height and breadth of the remaining dunes, and prepare the erosion potential of the next storm.