ABSTRACT

Kana, T.W.; Traynum, S.B.; Gaudiano, D.; Kaczkowski, H.L., and Hair, T., 2013. The physical condition of South Carolina beaches 1980–2010.

Thirty years of monitoring surveys and shoreline erosion studies (1980–2010) along the South Carolina coast show that artificial beach nourishment and the natural process of inlet shoal bypassing have advanced the shoreline along most of the developed beaches and barrier islands. Of the ∼98 mi (∼161 km) of developed beaches (including public parks), fully 80% were much healthier in 2010 than in 1980, as evidenced by burial of seawalls, wider berms, and higher dunes. About 15% of the developed beaches are in approximately the same condition as in 1980; the remaining ∼5% are considered in worse condition. The balance of South Carolina beaches (∼89 mi, ∼146 km) are principally wilderness areas with limited public access. The dominant condition of wilderness beaches is high erosion; limited new sand inputs, particularly via inlet bypassing; and accelerated recession as many of these sand-starved beaches wash over salt-marsh deposits. High erosion results from a combination of sand losses to the lagoon, winnowing of muddy marsh deposits outcropping across the receding beach, and longshore transport losses to the adjacent inlet. An estimated 75% of the undeveloped beaches in 2010 were well landward of their 1980 positions. Between 1980 and 2010, ∼39.4 million yd3 (∼30.1 million m3) of beach nourishment from external sources was added to developed and park beaches (∼62.6 mi, ∼102.6 km). This is equivalent to an addition of ∼168 ft (∼51 m) of beach width in the nourished areas. Natural shoal bypassing events appear to have added a similar magnitude of new sand along accreting beaches. Bypassing events at some beaches involved ∼2–5 million yd3 (1.5–3.8 million m3). Ebb dominance at many South Carolina inlets is shown to play an important role in preserving the littoral sand budget, maintaining large sand reservoirs for bypassing and helping maintain the developed beaches in the state. Low rates of erosion in other areas, such as the Grand Strand, combined with large-scale nourishment have advanced those beaches well beyond historic conditions.

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