Beach Erosion and Deposition on Dauphin Island, Alabama, U.S.A.

Abstract

Beach erosion and deposition along the Gulf of Mexico beaches of Dauphin Island, Alabama, were evaluated using air photos, beach profiles, visual wave observations, and historical coastal engineering archives. The eastern end of the island has two reaches of shorelines which are receding and a reach of shoreline in between them which is accreting. Shoreline recession was measured during the year of this study at rates up to 15 m/yr. Based on beach profile surveys, the changes observed this year are consistent with the changes that have occurred during the past decade. Averaged over the past decade, maximum recession fates of 6 m/yr were found. The recession/accretion/recession pattern at the eastern end of the island appears to be a response to changes in the position of the Mobile Pass ebb- tidal shoals and related ephemeral islands immediately offshore. Mobile Pass is one of the largest tidal inlets in the country. The shoals and Islands (commonly called Sand Island) provide both sand for the Dauphin Island beaches and wave sheltering to those beaches. The shoreline along the remainder of the Dauphin Island beaches to the west appears to have been generally stable during the past decade. Coastal engineering works which have modified the natural coastal processes of the Dauphin Island littoral system include coastal structures at the east end of the island and the removal of sand from the littoral system by dredging.