Application of a barrier island translation model to the millennial-scale evolution of Sand Key, Florida

The evolution of a barrier island and its stratigraphic architecture is investigated with the numerical model BIT (barrier island translation). The model simulates, with simplified equations, the effects of various processes (wind waves, storm surges, sea-level oscillations) on sediment location and characteristics. The presented formulation is able to reproduce both the cross-shore profile and the distribution of sediment facies in time.The model is based on two appropriate simplifying assumptions: (i) the conservation of the total mass of sediments and (ii) the conservation of the equilibrium cross-shore beach profile. Particular attention is devoted to the treatment of sediment reworking by wind waves and barrier overwash, which is induced by extreme events like storms and hurricanes, and causes a relative transport of sediments from the body of the sand barrier to the top of the island and to the back-barrier area. The model is applied to Sand Key, Florida. Model results show a satisfactory reproduction of the geometry and stratigraphy of the inner shelf, with the correct position of every stratigraphic facies within the barrier island. Simulations under different scenarios of sea-level rise during the last 8000 yr indicate that the rate of overwash and lagoonal deposition are critical for the survival of the barrier island under past sea-level oscillations.