Coastal Storms and Erosion
Hurricanes play a key role in massive erosion, as these storms generate a dangerous combination of high winds, currents and large waves that can be detrimental to a beach. In fact, several Hurricanes have been directly responsible for major changes in the coastal landscape.
In 1954, Hurricane Hazel made landfall near Calabash, North Carolina, halfway between Myrtle Beach, South Carolina and Wilmington, North Carolina, and it destroyed every pier along a 170-mile (270-kilometer) stretch of coastline. Hazel wiped out much of Garden City, South Carolina, especially its business district, where only three of the 275 buildings escaped damage and only two houses out of 275 remained habitable.
At landfall, Hazel brought a storm surge of 14.5 feet (4.4 meters) to a large area of coastline. Coastal damage was severe along the southeastern coast of North Carolina and the highest storm surge was recorded at Calabash, coincidentally arriving at the highest lunar tide of the year and reaching 18 feet (5.5 meters) above mean low tide. Southport and Wrightsville Beach were hit hard, with large portions of the landscape, homes, buildings and trees that were in this coastal area literally being wiped away to sea.
A more recent example happened in 2003, when Hurricane Isabel, a low category 2 hurricane, made landfall in Hatteras Village on the Outer Banks. With the strong winds and waves, the hurricane also brought what locals described as a "wall of water" that crushed the northern part of Hatteras Village and the neighboring southern village of Frisco. A number of homes were ruined and smaller beach cottages were dislodged from their pilings and pushed into the Pamlico Sound.
In between the towns, where a few miles of highway once connected the two villages, a new inlet formed, dubbed "Izzy's Inlet." The Federal Government spent weeks refilling the inlet, which was very deep with swift moving water, and this stretch of Hatteras Island once again appears to be back to normal, though locals remember just how delicate this barrier island truly is when it comes to hurricanes.
A good Nor'easter can also cause severe erosion to a coastline, and many folks believe a Nor'easter can be even more dangerous than a hurricane. While a hurricane only blows for a few hours before moving north, a Nor'easter can settle in for days, exasperating the damage to a coastline.
One area that is constantly hit by Nor'easters is the section of beach just north of Rodanthe on the Outer Banks called the "S-Curves." Once home to a wide area of beach that comfortably ran from the ocean to the Pamlico Sound, the highway has been moved further west twice over the past 20 years due to erosion caused by a series of Nor'easters.
Today, every time a Nor'easter hits the Outer Banks, this narrow stretch of highway floods severely, closing the road that connects Hatteras Island with the rest of the world. Though after each storm the North Carolina Department of Transportation (NCDOT) pushes sand back onto the dunes, locals know it is only a matter of time before the next Nor'easter will tear it down again and close the road.
As these examples show, the overall impact of storms on barrier islands depend upon qualities of the storm (the storm surge, the waves and the wind speed) and the elevation of the barrier island at landfall. To quantify the impact of storm damage, the United States Geological Survey (USGS) devised the following "hazard scale" which is divided into 4 "impacts," and accelerates in degree of damage caused by erosion:
- Impact 1 - Wave erosion is confined to the beach area. The eroded sands will be replenished in a few weeks to a few months and no significant change occurs in the system.
- Impact 2 - Waves erode the dune and cause the dune to retreat. This is a semi-permanent or permanent change to the system.
- Impact 3 - Wave action exceeds the dune's elevation, destroys the dune and pushes sediment from the dune landward (approximately 300 yards/100 meters), thereby creating overwash. This change in the system pushes the barrier island landward.
- Impact 4 - The storm surge completely covers the barrier island, destroys the dune system and pushes sediments landward (approximately 0.6 miles/1 kilometers). This is a permanent change to the barrier island or portions of it.