CAPE LOOKOUT Barrier Island Ecology of Cape Lookout National Seashore and Vicinity, North Carolina NPS Scientific Monograph No. 9

SHORELINE CHANGES

After retreating during storms, the beach will grow seaward. Soon after Ginger, a new berm began building outward with the return of gentler waves. Before that storm, we tried to get some idea of the changes in the beach width since the first survey by the U.S. Army Corps of Engineers in the early 1960s, when the Corps expressed considerable alarm about the beach erosion shown by their measurements. The beach had indeed retreated markedly, but those measurements were made soon after a particularly severe storm period. Repeating some of their measurements shows the changes during the last 8 years (Fig. 37). It is quite evident that, for the most part, the beach has been prograding since those storms. (Measurements were made at about the same time of year to avoid seasonal differences.) Indeed, it appears that nearly all of the loss during the storms has been recouped. Nevertheless, based on measurements from old maps, Core Banks appears to be retreating about 50 m per century.

Fig. 37. Shoreline changes during the period 1960-71. The permanent benchmarks established by the Corps of Engineers in 1960 were used to determine beach retreat, and the data for 1960-62 are from their report urging erosion control (U.S. Army Corps of Engineers 1964). Measurements were made from the benchmark at each profile to mean sea level on the beach. In the early 1960s there were several severe storms, and such recession would be expected. The beach widths were remeasured in a similar manner during our studies and at the same time of year. Since there were few severe storms from 1962 to 1971, accretion predominated on most of the beach. Obviously, measurement of the width of undeveloped beaches means nothing unless one knows the storm frequency in the years immediately before.