The Gulf of Mexico beaches of the eastern end of Dauphin Island have experienced some of the most dramatic shoreline recession on any inhabited barrier island in the United States in the past 30 years. The shoreline recession is over 500 feet in the vicinity of the Coast Guard R&R facility. The easternmost mile of the island is receding while the next mile of beaches to the west is accreting! This pattern is due to a shift of sand from the easternmost mile to the next mile to the west. Essentially, these beaches are re-aligning themselves to be more perpendicular to the incident wave climate. They are rotating to face more south-southeast instead of south. The location and elevation of the ebb tidal delta of Mobile Pass has a strong influence on this. Sand and Pelican Island as well as Dixie Bar are part of the ebb-tidal delta. The cause of the shift is a change in wave energy reaching Dauphin Island caused by the northwestward migration of Sand/Pelican Island and the loss of elevation of the shoals around the outer portion of the ebb-tidal delta (near the lighthouse on both Dixie Bar and Sand Island Bar).
The new sand shown here will migrate to the beaches in the background
Some of this shift of sand can be explained as natural shoreline fluctuations around an inlet. However, the shift has probably been increased by the Mobile Ship Channel. Over 20 million cubic yards of material dredged from the channel have been dumped offshore in the past 30 years. Most of this material is probably sand that would otherwise have been part of the outer bar of the ebb-tidal delta of Mobile Pass (i.e. in the shoals around the lighthouse). Thus, without the ship channel, the shoals around the lighthouse would have been higher and the shift of sand on the eastern end of Dauphin Island would have been less. This report recommends that sand dredged from the outer bar (south of Fort Morgan) be placed in these shoals or directly on the beaches of Dauphin Island. This would be a form of artificial sand bypassing that would replace the natural bypassing that has to be interrupted to maintain the ship channel.
Sand dredged from the boat channel into Billy Goat Hole sometimes gets placed on the beaches in the flank of the failed groin field (the offshore rocks) south of Fort Gaines. These small beachfills feed sand to the easternmost mile of beaches that are so eroded. However, sometimes, this sand is moved north towards the Pass Drury area on the artificial sand bar and beach that protect the Government Cut boat channel. In essence, this sand is being used to protect a navigation channel and not to protect the Gulf of Mexico beaches. This is an example of competition for the same sand resource that will probably become more common in Alabama’s future.