Seasonal erosion occurs when large winter waves pull sand off the beach and smaller summer waves return all or part of it. Beach and dune erosion near inlets can be particularly dramatic. Through inlet erosion, islands can migrate hundreds of feet each year, causing chronic beach loss at one end of the island and substantial beach build-up at the other. This is what is happening at Mason's Inlet near erosion-threatened Shell Island Resort, Rogers says. Hurricanes and other powerful storms also can cause damage when storm tides and high water levels erode large chunks of land from the beach and sand dunes.
Currents carry the sand to the bottom of the ocean and later bring it up under the beach.
This natural restoration may take place the following year or not until years later, if it occurs at all. If sand continues to erode without being replaced, chronic beach loss occurs. The best defense against this appears to be beach nourishment, Rogers says. The process is expensive, costing hundreds of thousands of dollars in annual maintenance, as the sand must be replaced every two to four years. But for areas dependent on tourism, beach nourishment can be worth the expense.