130. Folly Island, northeast of the inlet, has eroded landward and 

 alongshore to the northeast over the duration of these data. From 1854/58 to 

 1921, it retreated over 1,080 m in alongshore direction (16 m/year) . Along- 

 shore retreat continued to 1983, although at a reduced rate (2.5 to 3.4 m/ 

 year). Net change between 1854/58 and 1983 was alongshore erosion of approxi- 

 mately 1,200 m. Coincident with rapid erosion of Folly Island between 1854/58 

 and 1921 was the development of Bird Key between Folly and Kiawah Islands. It 

 was first mapped on the 1921 survey, where it had an area of 0.2 x 10 6 m 2 . 



Its surficial area has waxed and waned dramatically between 1921 and 1983. 

 Between 1921 and 1933, it lost 183,000 m 2 and then gained 1.1 x 10 6 m 2 by 1955. 

 The 1964 survey shows a tiny island only 7,000 m 2 in size, representing a 

 1.2 x 10 6 m 2 loss since 1955. In 1983, the key was 244,000 m 2 in area, repre- 

 senting a net increase of 48,700 m 2 since 1921. Small changes in position, 

 orientation, and shape accompanied these area changes. 



131. As a result of changes in Kiawah and Folly Islands and Bird Key, 

 throat width changed from 1,525 m in 1854/58, to a maximum of 2,560 m in 1921, 

 down to 1,700 m in 1955, and back up to 2,010 m in 1983. A net width increase 

 of roughly 500 m from 1854/58 to 1983 was due mainly to erosion of Folly 

 Island. 



Lighthouse Inlet (Map 13) 



132. Most changes that have occurred at Lighthouse Inlet are the result 

 of rapid shoreline erosion along Morris Island since completion of the 

 Charleston Harbor jetties. Net erosion rate between 1857/58 and 1983 is over 

 10 m/year for the southern end of Morris Island. Folly Island, south of the 

 inlet has also eroded landward since 1857/58, but the magnitude of change is 

 small compared with Morris Island. A prominent seaward offset of Folly Island 

 has resulted. The southern terminus of Morris Island has moved alongshore 

 only slightly during this period. Net change from 1857/58 to 1983 has been 

 about 60 m of southwest extension. Folly Island eroded southwest about 275 m 

 during this same interval; however, because of landward retreat of Morris 

 Island, the inlet throat retreated upstream and decreased in width by 120 m 

 over the study duration. 



Charleston Harbor (Map 13) 



133. The northwest side of Charleston Harbor entrance is formed by 

 Sullivans Island. Accretion in the vicinity of Fort Moultrie has been ade- 

 quately measured by the shoreline mapping technique. Southwest of Charleston 



110 



