New report on Hurricane Matthew’s dune damage in Florida

A new report by the United States Geological Survey tallies Hurricane Matthew’s damage to Florida’s coastline, including the creation of a new inlet and washed out beach roads.

The preliminary analysis, released Monday, found about 15 percent of the sand dunes on Florida’s Atlantic coast were overwashed by Hurricane Matthew, as the powerful Category 4 cyclone brushed the state last month.

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Damage includes a new inlet that was cut between the Atlantic Ocean and the Matanzas River near St. Augustine, which stripped away a 12-foot dune.

Low-altitude oblique photography taken before Hurricane Matthew (Sept. 6, 2014) and after (Oct. 13, 2016) shows the storm cut a new inlet between the Atlantic Ocean and the Matanzas River near St. Augustine, Florida, stripping away a 3.7 meter (12-foot) dune and carrying sand into the estuary.Public domain

Low-altitude oblique photography taken before Hurricane Matthew (Sept. 6, 2014) and after (Oct. 13, 2016) shows the storm cut a new inlet between the Atlantic Ocean and the Matanzas River near St. Augustine.

But the damage was not as bad as what experts had feared. Original impact estimates called for 24 percent of Florida’s Atlantic coast to be overwashed by the storm surge, said USGS research oceanographer Joseph W. Long.

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Low-altitude oblique photography taken before Hurricane Matthew (Sept. 6, 2014) and after (Oct. 13, 2016) in Flagler Beach, Florida, shows that waves washed away part of Highway A1A and obliterated a 5.2-meter (17-foot) dune.

Long and colleagues are working on a more detailed assessment of Hurricane Matthew’s coastline impacts, including comparing aerial photos taken in September 2014 with pictures take a week after Matthew went through.

“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,” Long said.  “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.”

Oblique aerial photographs at Stuart, Florida. Oblique aerial photographs collected before (top) and after (bottom) Hurricane Matthew. Storm waves the eroded beach, removing sand and exposing outcrops of old rock and shell deposits (red arrows). The yellow arrow in each image points to the same feature in both photos

Oblique aerial photographs at Stuart, Florida. Oblique aerial photographs collected before (top) and after (bottom) Hurricane Matthew. Storm waves the eroded beach, removing sand and exposing outcrops of old rock and shell deposits (red arrows). The yellow arrow in each image points to the same feature in both photos

In Palm Beach County, damage to beaches from Hurricane Matthew could top $29 million.

A report from the county’s Environmental Resources Management Office released last week says the “dry beach width” countywide was decreased by 32 percent from Matthew and the seasonal King Tide event that followed.

Palm Beach Post Staff Writer Bill DiPaolo found the worst erosion scars are exposed limestone at the beach at the Jupiter Civic Center and Coral Cove Park, but even south county, which felt the least effects of the storm, still had beach damage.

Beach erosion leaves major drops in the sand on the north end of Carlin Park in Jupiter. (Richard Graulich / The Palm Beach Post)

Beach erosion leaves major drops in the sand on the north end of Carlin Park in Jupiter. (Richard Graulich / The Palm Beach Post)

“The beach did its job. It protected the walkovers, roads, buildings and the dunes. Overall in the county there was moderate erosion,” said Dan Bates, the deputy director of the county’s Department of Environmental Resources Management.

The worst erosion was from Singer Island north to Coral Cove Park in Tequesta, which will cost about $13 million to repair. More erosion was in Palm Beach, Delray Beach and Boca Raton, said Bates. Those will cost $15.7 million to fix.

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