From Florida to North Carolina, Hurricane Matthew’s storm surge and waves overwashed the stretch of coast totaling 177 miles in four states.
Nearly two months after Northeast Florida's brush with Matthew, signs of the damage remain. Huguenot Park is closed indefinitely due to a road washout and condemned homes in Flagler and St. Johns counties sit precariously upon undermined seaside foundations.
Aerial photos mapped by the U.S. Geological Survey before the storm have been compared to images surveyed in the wake of Matthew. The analysis reveals an estimated 40 miles worth of dunes and other coastal structures were overtopped in Florida.
A preliminary review found 32 miles worth of shoreline in Georgia and 75 miles in South Carolina were overwashed, mostly in lightly populated areas. Rain was the biggest impact in North Carolina but storm tides also overtopped about 30 miles of dunes.
The Survey deployed 80 sensors from Miami to Jacksonville ahead of the storm, the largest such deployment in history. Tide gauges along the coast indicate storm surge reached just over 5 feet under the Beach Boulevard Bridge on Jacksonville Beach. Offshore wave heights in excess of 27 feet contributed to an additional 6 to 15 feet of wave runup at the shoreline. The combined effects of surge and storm-induced wave runup created elevated total water levels at the shoreline, causing extensive erosion of the beach and dunes.
In St. Augustine the surge was measured at 8 feet washing away a 16-foot sand dune, destroying oceanfront homes’ boardwalks and decks. Pictures south of St. Augustine show how the storm surge opened up a new inlet between the Atlantic Ocean and the Matanzas River, stripping away a 12-foot dune and carrying most of its sand into the estuary.
Powerful waves pack a punch and can weigh 2,000 pounds per cubic yard. Force like this easily rips apart sections of A1A in Flagler county where the dunes thin or become .
Healthy dunes absorb the punch explaining why some beaches suffered more than others. Aerial photos show how large wide dunes reinforced with sea oats and other plants absorbed more energy and held up better.
Those healthy dunes provided a sand source to buffer the waves. But, in locations where roads led directly to the beach, ocean water rushed over the sand and into neighborhoods.
You can view photos of the entire coastline yourself and compare before and after locations from the USGS website.