Studies of water-mass circulation and sediment transport adjacent to barrier islands of the Georgia coast indicate a more complex pattern of barrier-island development than has been previously suggested. The model here proposed emphasizes that shoal formation seaward from estuarine entrances is critical to development and growth of barrier islands.

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Shoal development on the north and south sides of estuarine entrances gives rise to 2 structurally different types of barrier islands. South-side shoals are triangular sand bodies attached to the shoreline. Through time these shoals prograde seaward and form arcuate beach ridges. Shoal and beach ridges are partly eroded during periods of high wave energy. The development of barrier islands (Type I) results when renewed shoal and beach ridge formation occurs seaward from these terminated ridges. Shoals on the north sides of entrances are detached from the shoreline and are segmented as a result of longshore spillover of channel water. Longshore trending shoals form seaward of "spillover channels." These shoals are the forerunners of recurving beach ridges which form barrier islands (Ty e II) on the north side of the channel. At the present time Type I and Type II barrier islands are developing on the Georgia coast.

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